**2.5 Complication avoidance**

Carotid artery injury is the most formidable complication of the EEA. Avoidance of carotid artery injury comes from meticulous planning, the use of stereotaxy, and adjunct tools including ultrasonography and fluorescence. Control of carotid artery injury can be achieved by an experienced two-surgeon team, and with coordination with anesthesiology and case support staff. We utilize a carotid artery injury "time out" to rehearse such a scenario in cases where the carotid artery may be encountered. This includes the possibility of endovascular sacrifice of the blood vessel, which is the safest immediate option in brisk bleeds. Endovascular sacrifice should only be attempted after hemorrhage is controlled.

#### **Figure 3.**

*A 7 year old male presented with vision changes and was diagnosed with craniopharyngioma on MRI with contrast (A) sagittal (B) coronal, (C) axial. This was resected by endonasal transsphenoidal approach. Post operative MRI (D-F) after gross total resection. A high flow CSF leak was identified intraoperatively, which was closed with a nasal septal flap and abdominal fat graft.*

#### *Pediatric Skull Base Tumors DOI: http://dx.doi.org/10.5772/intechopen.95605*

High flow venous bleeding should also be avoided, especially during exposure of the anterior intercavernous sinus. Bleeding from a robust intercavernous sinus can be brisk and is best avoided by isolating and dividing the sinus with cuts in the sellar and planum dura before moving forward in the exposure. Hemostatic agents and warm irrigation can aid in hemostasis from venous bleeding. Finally, while rare, carotid-cavernous fistula should be suspected in patients with mid-face or skull base trauma, and if present, treated before tumor resection is attempted.

CSF leaks are best avoided by respecting the arachnoid planes of dissection surrounding the tumor and sella. Entry into a subarachnoid cistern or ventricle can predict a CSF leak with confidence. We do not routinely use lumbar drainage for peri-operative care, unless such a leak is expected or encountered by misadventure. High flow CSF leaks can be addressed by raising a nasoseptal or turbinate flap for closure, though as described above, development of the septum and turbinates may lag behind development of the skull base and limit coverage of the flap (**Figure 3**).

Persistent leak can predispose a patient to developing tension pneumocephalus. Multi-layered closure can help prevent this rare complication, which is thought to arise from a ball-valve effect of air entry into the resection bed and intracranial compartment. CSF leaks can also confer a risk for meningitis and ventriculitis, and positive pressure ventilation (CPAP) is strictly avoided peri-operatively.


**4. Conclusions**

Our results revealed that LMW-ulvan enzymatic production of ulvan extracted from green algae U. pertusa consists of 57.23% rhamnose, 28.76% xylose, 7.42% glucuronic acid, and 1.77% glucose. Its backbone contained (1 →3,4)-linked Rha, (1 →4)-linked Xyl, and (1 →4)-linked GlcA with small amounts of (1 →4)-linked Rha residues; sulfate substitution was at C-3 of rhamnose. In addition, LMW-ulvan was able to relieve intestinal inflammation and oxidative damage caused by DSS. Meanwhile, LMW-ulvan was able to significantly increase mRNA levels of claudin, occluding, and ZO-1, which improve intestinal mucosal permeability. Consequently, the results of this study support the potential application of LMW-ulvan as a functional food ingredient for IBD.

**Author Contributions:** Conceptualization, Y.L. (Yuanyuan Li), R.L., and Y.L. (Yinping Li); Methodology, Y.L. (Yuanyuan Li), R.L., and Y.L. (Yinping Liu); Formal analysis, Y.L. (Yuanyuan Li), H.Y., T.W., P.W., and Y.T.; Investigation, Y.L. (Yuanyuan Li), H.Y., J.Z., and Y.L. (Yinping Li); Data curation, Y.L. (Yuanyuan Li); Writing, Y.L. (Yuanyuan Li), R.L., and Y.L. (Yinping Li); Visualization, Yuanyuan Li; Supervision, R.L. and Yinping Li; Project administration, R.L. and Y.L. (Yinping Li); Funding acquisition, R.L. and P.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Comprehensive Management of Marine Ecological Environment and Risk Emergency Handling No.2019-Environment Protection Project-070, the Key Project of New and Old Energy Transformation in Shandong Province, and Research project of ecological environment protection and restoration of Yangtze River in Zhoushan (No. SZGXZS2020068).

**Conflicts of Interest:** The authors declare that they have no competing financial or non-financial conflict of interests.


*3.4. Risk Assessment*

The modified risk graph presented Figure 3 visualises the assessment of the risk of portable lithium-based batteries. Two specific scenarios were chosen representing the observed areas of (1) collection and (2) treatment of waste from Table 8.

**Figure 3.** Modified risk graph for the two scenarios of Table 8: Waste collection (a small fire in a collection vehicle, CV) and waste treatment (a fully developed fire in a treatment plant, TP).

Keeping the grading of the probability of occurrence in mind, the various probabilities do not lead to different results in the risk graph, whether residual waste or lightweight packaging waste; however, they vary considerably in Table 8.

### **4. Discussion**

A broad spectrum of potential hazards of batteries was considered within this study's investigations and it is presented in Table 5, being exemplary for residual household waste. However, from a holistic viewpoint, in complex systems, such as waste management systems, it is unlikely to cover all of the possible hazards that are posed by lithiumbased batteries.

As [25] stated, risk matrixes may be subject to biases or errors. A risk matrix can compare only a small fraction of more or less randomly selected hazards due to their low resolution. In general, that fact has to be kept in mind when risk graphs are created or the basis of decision-making.

The scenarios that were observed in detail reveal that the risks are either in the ALARP region (yellow area) or in the region of inacceptable risks (red area of the risk graph). For the latter, measures of risk reduction are inevitable.

Fires in waste collection vehicles have become a well-known phenomenon in recent years. The smoke of the fires is usually recognised by the vehicle drivers in an early stage. An unspoken best-practice measure of the respective vehicle driver is to choose a known asphalt or concrete surface that is big enough to unload the burning waste (e.g., parking area of a nearby supermarket) and call the local fire brigade. The waste is usually pulled apart during extinguishing in order to speed up the subsequent fire-fighting operations and to locate the origin of the fire.

The different results for RHW and LPW indicated that waste shredders are the main hot-spot for battery-caused waste fires. In contrast to shredders, bag openers in LPW sorting plants are not crushing the waste. That is also confirmed by a recently published study [26], revealing high numbers of battery-caused ignitions after pre- and post-shredders in treatment facilities for RHW and commercial waste.

The comparison of the data of potential fire incidents per year with values from literature allows for an overall evaluation of these results. In contrast to the statistical data of waste fire incidents [1,27], where relatively low numbers are determined battery-caused fires, the results of this study seem to be very high. The data of [1,27] are characterised by high shares of unknown fire causes, which probably underestimates the relevance of battery-caused fires. In contrast to the high numbers of heat-related threshold exceedances in waste shredding machines found by [26], which are caused by batteries to a large extent, the results of this study seem appropriate. Autischer et al. [26] detected 0.1 to 1.5 threshold exceedances per eight-hour-work shift, depending on the respective measuring point in one of the two observed treatment plants. That means 260 to 1.580 threshold exceedances per year and treatment facility. In comparison to the results, it should be noted that (1) both treatment plants process significantly less than 100,000 tonnes per year and (2) temperature-related threshold exceedances are detected—not fire incidents.

### **5. Conclusions**

In this article, the main influence factors on lithium-based portable batteries' risk were investigated in their end-of-life phase. The degree of damage that was happening to portable batteries was investigated and compared for different waste streams. After that, the hazards and potential risks were modelled and assessed, including the present and previous studies' findings.

The results included a detailed analysis of the damage degree, the distribution pattern of influencing characteristics of portable batteries, and profound risk analysis and assessment.

The assessment reveals that the risk of lithium-based portable batteries is significantly too high, which makes it difficult to maintain modern waste management in a sustainable way. Primarily, municipal solid waste treatment plants are at increased risk. The probability that treatment plants burn to the ground is far too high, according to the available assessment. The increased number of major fires in waste management in recent years is clear and undeniable evidence.

No other substance or material has ever comparably endangered the whole waste industry. Hence, besides research and development activities for investigating and understanding the hazards and risks of lithium-based portable batteries, increased technological development and innovation efforts are indispensable for reducing the risk potential of end-of-life portable batteries.

In order to reduce risk, the waste sector has to aim to collect as many batteries as possible in the separate collection systems and take-back schemes, as only this collection system guarantees a damage-free return system. That requires increased effort in public relations and consumer awareness-raising. However, a 100% separate collection rate for portable batteries is highly unrealistic without a comprehensive deposit system. Hence, operators of treatment facilities have to find ways to (1) protect critical infrastructure and treatment processes (e.g., including new detection and extinguishing methods) or (2) preferably detecting and separating portable batteries in the course of their treatment processes.

Further research is necessary in order to gain more specific knowledge on the influence factors, where assumptions had to be made in the present study. Especially, the probability of waste ignition due to the thermal runaway of portable batteries has to be investigated.

**Supplementary Materials:** The following are available online at https://www.mdpi.com/2227-971 7/9/1/49/s1.

**Author Contributions:** Conceptualization, T.N. and R.P.; Data curation, T.N. and M.B.; Formal analysis, T.N. and M.B.; Funding acquisition, R.P.; Investigation, T.N. and M.B.; Methodology, T.N. and M.H.; Project administration, T.N.; Resources, T.N. and R.P.; Software, T.N.; Supervision, R.P.; Validation, T.N., M.H. and R.P.; Visualization, T.N.; Writing—original draft, T.N. and M.H.; Writing review & editing, T.N. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Austrian Research Promotion Agency, grant number 850753.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy restrictions.

**Acknowledgments:** The authors thank T. Bäck, L. Kranzinger, P. Puchbauer, W. Rübenbauer, S. Schlögl, B. Steiner, and the members of the Chairs working group 'Environmental Analytics' for their support in the sampling and sorting campaign. Furthermore, the authors thank the Austrian Research Promotion Agency for funding and the project partners for support.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

### **References**


**5. Conclusion**

The study found *E. coli* with most ESBL producing strains. Multiple drug resistance was a common occurrence; in almost all the Gram negative uropathogens characterized, 100% resistance was recorded. ESBL strains generally showed greater resistance than the non-ESBL strains particularly to the cephalosporins and β-lactam antibiotics. However resistance to UTI empirical drugs and other commonly used antibiotics were alike in both ESBL and non-ESBL strains as low susceptibility was observed. An important finding was the considerable resistance of the ESBL strains to the aminoglycosides and imipenem which are last line treatment drugs. The results of the study clearly indicate the need for antimicrobial stewardship and enhanced infection control measures in our hospitals. Routine screening of ESBLs in our hospitals is highly recommended since appropriate antimicrobial therapy can only commence with early detection of these strains.


**Abstract**

Ciliates are important elements of the trophic networks of aquatic and terrestrial environments, they can be primary producers (myxotrophs), consumers of bacteria, algae, flagellates, even other ciliates and can serve as food for metazoans, for all the above they are the link between different levels of food webs. The structure of the ciliates varies according to the seasons of the year and depending on the trophic conditions of the aquatic systems. Ciliated communities have modifications and adaptations in response to environmental perturbations. The objective of this chapter is to describe the importance of different trophic groups of ciliates in different ecosystems, including anthropogenic perturbations and their impact on trophic webs.

**Keywords:** ciliates, trophic groups, food webs, perturbations


*2.3. Animals and Experimental Design of the CCl4-Induced Hepatotoxicity*

To test the potential hepatoprotective effects of olive leaf extracts, experiments were conducted in six groups according to the following administration (Scheme 1): group I—negative control with administration of vehicle only (corn oil); group II—administration of carbon tetrachloride (CCl4) in corn oil 50 μL/kg [39]; group III—daily administration of fresh leaf extracts dissolved in corn oil (FLE, 30 mg/kg); group IV—daily administration of dried leaf extracts dissolved in corn oil (DLE, 30 mg/kg); group V—administration of FLE (30 mg/kg) and simultaneous treatment with CCl4 (50 μL/kg) +; group VI—administration of DLE (30 mg/kg) and simultaneous treatment with CCl4 (50 μL/kg).

**Scheme 1.** Graphical scheme summarizing the experimental design, *n*: number of rats.

The CCl4 was administered by gastric gavage twice per week (on every Tuesday and Thursday) over eight weeks. A daily pretreatment with FLE or DLE was realized 7 days before CCl4 exposure and then daily throughout the research work by gastric gavage. The rats were sacrificed at the end of eight weeks and 24 h after the last dose of the hepatotoxin.


**4. Conclusions**

accumulating

generated by the Peltier module, which

chamber.

 on the top wall. The design

We found that by infusing calcium chloride into a cellulose sponge, faster moisture absorption and an increase in the maximum water uptake capacity (at 27 ◦C and 80% RH) up to ~305% were achieved compared to that without the sponge at ~272%. The sponge inhibited common problems caused by calcium chloride, such as agglomeration and its deliquescence. The approach is simple, and relatively more cost effective compared to other moisture absorber materials. Cellulose sponge as a medium is simple, cheap, and environmentally friendly; energy efficient; and effective when absorbing moisture, as shown by the salt absorbing moisture up to ~305%. A proof-of-concept device was also demonstrated, utilizing a three-channel water collection pathway using a Peltier device to generate the clean water from atmospheric moisture.

**Author Contributions:** Conceptualization, J.L., T.B., E.T., D.J.M. and E.S.; formal analysis, J.L., E.J., and E.S.; investigation, J.L., T.B., E.T. and D.J.M.; writing, J.L., E.J. and E.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by SPH Applied Science Academy Program at Sekolah Pelita Harapan Lippo Village, period 2022–2024.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Acknowledgments:** We thank Sekolah Pelita Harapan, Universitas Pelita Harapan and Emmerich Research Center for their generous support in providing lab access throughout this research study.

**Conflicts of Interest:** The authors declare no conflict of interest.


**8. Peri-operative considerations in rheumatoid patients undergoing arthrodesis**

A complete assessment of the patient by an internal medicine physician and an anaesthetist is vital prior to the patient undergoing general anaesthesia. Cardiological manifestations such as pericarditis, arrhymthmias, and valvular incompetence occur at much greater incidence in this cohort when compared with their peers (Conlon et al 1966, Del Rincón. et al 2001). Similarly rheumatoid patients have twice the mortality rate from pulmonary disease (Gonzolez–Juanatey et al 2003). We do routinely monitor these patients in a high dependency setting postoperatively, until they are stable enough to be transferred to a low dependency and rehabilitation setting. Anaemia is a common finding in patients with well established rheumatoid arthritis (Doyle et al 2000), though in our experience pre-operative transfusion is the exception as opposed to the rule. It is our practice to continue intravenous antibiotics for a period of 3 days post-operatively, with the initial dose being administered at time of induction, due these patients tendency to develop both early and late infections (Maury et al 1988, Wimmer et al 1998, Carpenter et al 1996).

A particularly difficult issue for surgeons to grapple with is the question of when to discontinue disease modifying drugs. Though a recent trial failed to show any significant difference (Grennan et al 2001),these medications had previously been shown to delay wound healing, a most undesirable complication in an already vulnerable group of patients (Abhilash et al 2002, Hamalainen et al 1984). Our practice is to discontinue such medications four weeks prior to surgery, having discussed the case with the patient's rheumatologist.

Surgical Considerations of Rheumatoid Disease

(Ebraheim et al 2000).

Involving the Craniocervical Junction and Atlantoaxial Vertebrae 287

foraminae or aberrant vertebral artery (Ebraheim et al 1998, Golanki & Crockard 1999, Nagaria et al 2009). We routinely use stealth neuronavigation when planning screw trajectories to minimise the risk to both vertebral arteries and neural structures. In our experience myelopathic patients who have successful reduction and immobilisation of the C1C2 segment will not require laminar decompression. In cases of aberrant vertebral arteries we place a unilateral transarticular screw, with a lateral mass screw in C1 and a pars screw in C2 being placed on the "aberrant" side, if safe to do so, however, an aberrant vertebral artery can also preclude safe C2 pars screw insertion and we have not experienced any failures over a 15 year period with unilateral screw placement. Though some authors routinely reinforce their constructs with a Gallie or Brooks fusion, this has not been our practice. Successful placement of bilateral transarticular screws provides 38mm of fixation which more than adequately stabilises the segment (Yoshida et al 2006), without the added 5 - 7% risk of neurologic injury associated with wire constructs

Having applied the Mayfield skull clamp either to the skull or to the halo ring itself if previously applied, an image intensifier is used to confirm correct alignment of the atlantoaxial joint and the subaxial cervical spine. A midline posterior incision from C1 arch to C2/C3 spinous interspace level is followed by a subperiosteal exposure of both atlas and axis, and of the occiput itself in cases of occipitocervical fusion. The posterior arches of C1 and C2 are exposed at C1 as far laterally as the medial border of the lateral mass and inferiorly as far as the C2/3 joint avoiding disruption of the joint itself. The destruction wrought by the rheumatoid inflammatory process on the normal anatomical landmarks of the atlas and axis makes placing C1-C2 screws without the use of neuronavigation hazardous at best, and foolhardy in some cases. The pars of C2 is exposed subperiostially as far as the C1/C2 joint remaining anterior to the traversing C2 root. Blunt dissection along the superior aspect of the C2 lamina allows the operator to appreciate the medial aspect of the C2 pedicle. Successful identification of the C2 pedicle and the pars as it extends superiorly toward the C1-C2 articulation, allows a safe entry into the C1-C2 joint. It is important in this area to maintain a subperiosteal approach with a sharp dissector to avoid venous haemorrhage. The joint may be entered, curetted and graft inserted directly. This step may be facilitated with the use of an operating microscope. It has been our practice to perform this additional step where the space between the articular surfaces of C1 and C2 allow it, particularly in those cases with incomplete reduction of C1 on C2. The approximate entry point for transarticular screw placement is 2mm lateral to the medial border of the C2-C3 facet joint. Stab incisions as per image guidance bilaterally allow the desired screw trajectory aiming toward the upper half of the C1 anterior tubercle. Use of neuronavigation to confirm screw trajectory minimises the danger of encountering either the vertebral artery (which may easily be damaged with a lateral or inferior trajectory (Geremia et al 1985) or the spinal cord. The vertebral artery is most at risk from a trajectory that is too low rather than one that is too lateral. This is especially important in cases when incomplete reduction of C1 and C2 has been achieved where an anterior target above the tubercle of C1 should be chosen. In these cases the choice of the anterior tubercle of C1 as a target causes a low trajectory through C2 with the risk of cortical perforation inferiorly. If this is kept in mind, incomplete reduction of C1 on C2 does not preclude C1/C2 transarticular screw fixation. An image-guided drill-guide is passed percutaneously to the posterior arch of C2, and aligned with the planned entry point on the neuronavigation. A guide K-wire is drilled

Such disease-modifying agents are recommenced after a period of 12 weeks to allow the maximum bony fusion to occur around the arthrodesis. The one exception in the disease modifying drug group is glucocorticoids. Rheumatoid patients have commonly been receiving oral glucocorticoids as a adjunct to other agents for a few decades by the time surgical intervention is recommended. By such a stage the hypothalamic-pituitary-adrenal has been completely suppressed, placing them at risk of an Addisonnian crisis if such medications are not administered. A large bolus of steroids is usually administered at the same time as that of antibiotics, with "stress-doses" continued for 3 days post-operatively. Due to the severity of the subluxation and deformity seen in the spines of these patients, along with accompanying cricoarytenoid and temporomandibular arthritis (Chen et al 2005, Paulsen 2000), the anaesthetists fibreoptically place the endotracheal tube whilst the patient remains awake.


*Article* **Laser Dissimilar Welding of AISI 430F and AISI 304 Stainless Steels**

**Krzysztof Pa ´ncikiewicz 1,\* , Aleksandra Swierczy ´nska ´ 2 , Paulina Hu´cko 1,3 and Marek Tumidajewicz 4**

Received: 24 September 2020; Accepted: 8 October 2020; Published: 13 October 2020

**Abstract:** A dissimilar autogenous laser welded joint of AISI 430F (X12CrMoS17) martensitic stainless steel and AISI 304 (X5CrNi18-10) austenitic stainless steel was manufactured. The welded joint was examined by non-destructive visual testing and destructive testing by macro- and microscopic examination and hardness measurements. With reference to the ISO 13919-1 standard the welded joint was characterized by C level, due to the gas pores detected. Microscopic observations of AISI 430F steel revealed a mixture of ferrite and carbides with many type II sulfide inclusions. Detailed analysis showed that they were Cr-rich manganese sulfides. AISI 304 steel was characterized by the expected austenitic microstructure with banded δ-ferrite. Martensitic microstructure with fine, globular sulfide inclusions was observed in the weld metal. The hardness in the heat-affected zone was increased in the martensitic steel in relation to the base metal and decreased in the austenitic steel. The hardness range in the weld metal, caused by chemical inhomogeneity, was 184–416 HV0.3.

**Keywords:** laser welding; austenitic stainless steel; martensitic stainless steel; dissimilar welded joint; microstructure; sulfide inclusions

#### **1. Introduction**

The development of technology is aimed at reducing production and operating costs, increasing the safety of use and improving ecology in the context of the development of materials. This opens the possibility of using new materials, developing the existing ones and modifying their properties [1]. Particularly in the area of welded joints, especially dissimilar joints, there are many opportunities due to the multitude of materials, processes and additional treatments that can significantly affect the final product.

AISI 430F (X12CrMoS17) is a stainless steel with the addition of sulfur typically existing in the form of MnS inclusions, which improves the machinability of this material. Despite the high chromium content, the addition of sulfur lowers the resistance to crevice and pitting corrosion. Depending on the type of treatment, it has a ferritic or ferritic-martensitic structure [2]. This steel is not recommended for use in marine environments and highly oxidizing chemical environments. It is used in the production of screws, spindles, nuts, medical instruments, and in the automotive and transport industry. Due to its applications, this steel can be subjected to plasma nitriding or nitrocarburizing to increase hardness, corrosion, tribocorrosion and wear resistance [3–5].

AISI 304 (X5CrNi18-10) steel is a very popular grade of austenitic stainless steel, with good corrosion resistance. It is used in the construction, automotive, food, and chemical industries, for decorative purposes and kitchen equipment, as well as an element of electronic equipment [6]. There have been many studies describing the corrosion resistance, mechanical and functional properties of this steel [7,8]. Currently, many studies have focused on possible ways to improve the properties of AISI 304 steel [9–11].

The weldability of steel depends primarily on its chemical composition, structure, mechanical and physicochemical properties. Therefore, dissimilar steels usually require special care to be able to join them [12–14]. The basic difficulties include differences in the values of thermal expansion coefficients, melting points, mechanical properties, electrochemical potential as well as the formation of intermetallic compounds [15]. Additional difficulties may arise from the need to meet different heat treatment requirements for each of the welded materials. Dissimilar joints are characterized by a non-linear change of properties and often a very unfavorable segregation of elements, which may eliminate them from service. In addition, dissimilar joining requires extensive technical knowledge, appropriate equipment and careful selection of consumables. However, these inconveniences and risks are taken due to the many benefits that arise from combining two very different materials, reducing both production and operating costs and the improving mechanical properties of the joints [16,17]. In order for such a joining to be carried out without unacceptable imperfections, it is necessary to thoroughly understand the technologies and weldability of materials.

AISI 430F steel is usually regarded as difficult to weld due to, among other factors, hydrogen-induced cold cracking, lack of weld ductility, intergranular corrosion, deterioration of toughness and corrosion resistance. In order to carry out the welding it is necessary to use pre-heating at 150–200 ◦C, which reduces diffusible hydrogen content and welding stresses. Additionally, post-weld annealing at 790–815 ◦C can be performed. To reduce the risk of intergranular corrosion, chrome depletion at grain boundaries should be decreased by the use of low heat input value. Despite so many difficulties, the literature shows that there have been few effective attempts to weld this steel grade, mainly to make dissimilar joints in such applications as pressure vessels or fuel injectors. Khan et al. [18] investigated laser beam welding of dissimilar AISI 430F and AISI 440C stainless steels and the effects of laser welding parameters and heat input on weld bead geometry. They obtained qualitatively sound joints by finding appropriate welding parameters to avoid micro-crack formation. Romoli et al. [19] made a dissimilar AISI 440C with AISI 430F laser welded joint and found an empirical relationship between the shear strength of the weld and the configuration adopted during experiments. They observed that higher susceptibility to surface crack formation generated on the boundary of the weld seam with AISI 440C is connected with a higher martensitic volume fraction.

AISI 304 steel is considered to be easily weldable, with the use of specific technological procedures, such as ensuring that the interpass temperature does not exceed 200 ◦C. However, it should be remembered that the heat introduced into the material during welding makes it more sensitive to intergranular corrosion and solidification cracking. Pankaj et al. [20] investigated the possibility of laser welding of AISI 304 steel with low carbon steel and found a correlation between heat input and the properties of the joints. Rogalski et al. [21] welded 304L steel with Incoloy 800HT and conducted an analysis of the properties and structure of the joint, confirming that the TIG method can be used to join these materials even with an unfavorable design resulting from the working conditions of the joint. On the other hand, Pa´ncikiewicz et al. [22] indicated in their work that although austenitic steels are treated as easily weldable, they cannot be ignored and potentially dangerous imperfections should be identified using both traditional and new test methods. At the same time, Kurc-Lisiecka et al. [23] obtained the sound joints during laser welding of AISI 304 steel in a wide range of welding parameters, confirming the good weldability of this material, even when using a concentrated heat source. Welding of AISI 304 austenitic steel with AISI 430 ferritic steel was performed by Wang et al. [24]. They used the gas tungsten arc welding process, assessed the structure and corrosion resistance of welded joints and proved that it is possible to obtain the correct joint between these steels.

Laser welding by concentrating the heat source provides many opportunities compared to the conventional arc welding: simplicity of automation, very narrow HAZ, slight material deformation, deep penetration without the need for beveling and the use of filler metal [25,26]. These features make laser technologies are constantly evolving so that the expensive equipment, which is necessary in this method, is becoming more accessible and at the same time the process simulation programs are more and more accurate [27,28]. In addition, laser welding was initially considered unsuitable for difficult-to-weld materials and carried a high risk due to the concentrated heat source. A lot of research has been done on the possibility to use laser welding for joining various materials and show that this method makes it possible to obtain high quality welded joints using the wide range of conditions and parameters [29–31]. conventional arc welding: simplicity of automation, very narrow HAZ, slight material deformation, deep penetration without the need for beveling and the use of filler metal [25,26]. These features make laser technologies are constantly evolving so that the expensive equipment, which is necessary in this method, is becoming more accessible and at the same time the process simulation programs are more and more accurate [27,28]. In addition, laser welding was initially considered unsuitable for difficultto-weld materials and carried a high risk due to the concentrated heat source. A lot of research has been done on the possibility to use laser welding for joining various materials and show that this method makes it possible to obtain high quality welded joints using the wide range of conditions and parameters [29–31].

*Materials* **2020**, *13*, x FOR PEER REVIEW 3 of 15

Laser welding by concentrating the heat source provides many opportunities compared to the

Each of the previously discussed steel grades can cause some problems during and after welding. According to the literature, each of the steel grades was subjected to laser welding, but there are no data on the possibility of laser beam welding of AISI 430F steel with AISI 304 steel. The purpose of this work was to analyze the possibility of making the overlap autogenous welded joint with the use of laser beam welding and to show the mechanism of structure formation in this welded joint. This goal was achieved by metallographic macro- and microscopic observations, EDS analysis, simulations and hardness measurements. Each of the previously discussed steel grades can cause some problems during and after welding. According to the literature, each of the steel grades was subjected to laser welding, but there are no data on the possibility of laser beam welding of AISI 430F steel with AISI 304 steel. The purpose of this work was to analyze the possibility of making the overlap autogenous welded joint with the use of laser beam welding and to show the mechanism of structure formation in this welded joint. This goal was achieved by metallographic macro- and microscopic observations, EDS analysis, simulations and hardness measurements.

#### **2. Materials and Methods 2. Materials and Methods**

The overlap joint of AISI 430F drill rod and AISI 304 tube (Ø25 × 2.5 mm) was welded by the 521 laser beam welding (LBW) process without a filler metal. A general view and the design of the welded joint are presented in Figure 1. This joint, a part of a specialized drill produced by RaQun Sp. z o.o. (Gorlice, Poland) for the mining industry, was made during the start of development and first testing of the welding procedure qualification. The overlap joint of AISI 430F drill rod and AISI 304 tube (Ø25 × 2.5 mm) was welded by the 521 laser beam welding (LBW) process without a filler metal. A general view and the design of the welded joint are presented in Figure 1. This joint, a part of a specialized drill produced by RaQun Sp. z o.o. (Gorlice, Poland) for the mining industry, was made during the start of development and first testing of the welding procedure qualification.

**Figure 1.** The welded joint: (**a**) general view, (**b**) design. **Figure 1.** The welded joint: (**a**) general view, (**b**) design.

Visual testing was performed according to European Standards ISO 17637 and EN 13018 by direct method in intense lighting ~600 lx with universal welding gauge, with resolution 0.05 mm. Chemical composition of base metals was measured by optical emission spectroscopy (OES) using a Foundry Master-WAS Spectrometer (Hitachi, Tokyo, Japan). Macro- and microscopic examinations were performed on two cross sections after mechanical grinding, polishing and two-step etching: chemical in Kalling's reagent (5 g CuCl2 + 100 ml HCl + 100 ml C2H5OH) and electrolytic in 10% CrO3 water solution. Base metals, heat-affected zones and weld metal were examined. Microstructure was characterized using a light microscope (Leica, Wetzlar, Germany) and scanning electron microscope (SEM) (Japan Electron Optics Laboratory Co., Ltd., Tokyo, Japan) with X-ray energy-dispersive Visual testing was performed according to European Standards ISO 17637 and EN 13018 bydirect method in intense lighting ~600 lx with universal welding gauge, with resolution 0.05 mm. Chemical composition of base metals was measured by optical emission spectroscopy (OES) using aFoundry Master-WAS Spectrometer (Hitachi, Tokyo, Japan). Macro- and microscopic examinationswere performed on two cross sections after mechanical grinding, polishing and two-step etching: chemical in Kalling's reagent (5 g CuCl2 + 100 mL HCl + 100 mL C2H5OH) and electrolytic in 10% CrO3 water solution. Base metals, heat-affected zones and weld metal were examined. Microstructure wascharacterized using a light microscope (Leica, Wetzlar, Germany) and scanning electron microscope(SEM) (Japan Electron Optics Laboratory Co., Ltd., Tokyo, Japan) with X-ray energy-dispersive

spectroscopy (EDS) (Japan Electron Optics Laboratory Co., Ltd., Tokyo, Japan). The depth of EDS analysis was assessed by CASINO v<IP_ADDRESS> software (Université de Sherbrooke, Sherbrooke, QC, Canada). Thermodynamic analyses were performed by Thermo-Calc 2020a (Thermo-Calc Software AB, Solna, Sweden) with the TC-FE7 database (Thermo-Calc Software AB, Solna, Sweden). Hardness measurements were performed by the Vickers method (2.942 N) on a Tukon 2500 universal hardness tester (Wilson, NY, USA) in 8 rows of 25 indentations on the cross section of the joint. The distance between the indentations was 0.2 mm and indentation time was 5 s. *Materials* **2020**, *13*, x FOR PEER REVIEW 4 of 15 spectroscopy (EDS) (Japan Electron Optics Laboratory Co., Ltd., Tokyo, Japan). The depth of EDS analysis was assessed by CASINO v<IP_ADDRESS> software (Université de Sherbrooke, Québec, Canada). Thermodynamic analyses were performed by Thermo-Calc 2020a (Thermo-Calc Software AB, Solna, Sweden) with the TC-FE7 database (Thermo-Calc Software AB, Solna, Sweden). Hardness measurements were performed by the Vickers method (2.942 N) on a Tukon 2500 universal hardness tester (Wilson, NY, USA) in 8 rows of 25 indentations on the cross section of the joint. The distance

#### **3. Results and Discussion** between the indentations was 0.2 mm and indentation time was 5 s.

Chemical compositions of base metals, verified by the OES, and weld metal, verified by the EDS, are presented in Table 1. The compositions comply with the requirements of product standards. The main alloying elements in AISI 430F steel were 15.5% chromium for corrosion resistance and almost 0.5% of sulfur for machinability in automatic machining processes. AISI 304 steel contains 18% chromium and 8% nickel to provide an austenitic structure with δ-ferrite at ambient temperature. **3. Results and Discussion**  Chemical compositions of base metals, verified by the OES, and weld metal, verified by the EDS, are presented in Table 1. The compositions comply with the requirements of product standards. The main alloying elements in AISI 430F steel were 15.5% chromium for corrosion resistance and almost 0.5% of sulfur for machinability in automatic machining processes. AISI 304 steel contains 18%

**Table 1.** Chemical composition of base metals (OES) and weld metal (EDS). chromium and 8% nickel to provide an austenitic structure with δ-ferrite at ambient temperature.

The butt welded joint was B quality level (acc. to EN ISO 13919-1) in visual testing (VT) and was C quality level in macroscopic examination. Full penetration and a few gas pores were observed (Figure 2). The largest pore was 0.16 mm in diameter and all the pores occupied 1.2% of the weld area (Table 2). For C quality level, the maximum dimension of the pore (with a tube thickness of 2.5 mm) was 1 mm and the maximum dimension of the area of the imperfection related to the projected area was 2%. Weld metal - 0.7 1.9 - 0.2 16.8 0.4 4.5 - - The butt welded joint was B quality level (acc. to EN ISO 13919-1) in visual testing (VT) and was C quality level in macroscopic examination. Full penetration and a few gas pores were observed (Figure 2). The largest pore was 0.16 mm in diameter and all the pores occupied 1.2% of the weld area (Table 2). For C quality level, the maximum dimension of the pore (with a tube thickness of 2.5 mm) was 1 mm and the maximum dimension of the area of the imperfection related to the projected area was 2%.

**Figure 2.** Macrostructure of the welded joint. **Figure 2.** Macrostructure of the welded joint.

Figure 3 presents the microstructure on the AISI 430F steel side of the joint. Base metal (Figure

**Table 2.** The results of the weld and pores surface area measurements.

Figure 3 presents the microstructure on the AISI 430F steel side of the joint. Base metal (Figure 3d) was characterized by a mixture of ferrite and carbides, which indicates a soft annealing or a high tempering delivery condition. This is a particularly favorable condition for machining due to the avoidance of a martensitic structure and low hardness. Gray inclusions elongated in the rolling direction, characteristic of manganese sulfides, were also observed (Figure 3d). The shape of the inclusions suggests that they are type II sulfides, acc. to Sims's classification [32]. EDS analysis confirmed the high content of manganese and sulfur, and additionally the inclusion was enriched by chromium (Figure 4), as indicated by a similar chromium content in the inclusion and the matrix. In high chromium steels it is possible to enrich the inclusions with this element. Considering also the small amount of iron, pyrrhotite with the formula (Cr, Fe, Mn)S can be formed [33–35]. Atomic concentration analysis indicates a 3:1 ratio between iron+manganese and chromium, and a 1:1 ratio between metallic elements and sulfur; thus, the observed inclusions were [(Fe,Mn)3Cr]S.

In the heat-affected zone, Figure 3b, intercritical HAZ (ICHAZ, heated to the δ + γ + MnS range) and coarse-grain HAZ (CGHAZ, heated much above A3) were observed. In ICHAZ an incomplete normalized microstructure with fine and medium grains and more carbides than base metal (Figure 3e) and in CGHAZ an overheated microstructure with coarser grains than in other zones were observed (Figure 3c). Due to the presence of a higher content of ferrite stabilizers (particularly chromium), martensite with δ-ferrite was observed, clearly visible in CGHAZ (Figure 3c). With increasing chromium content, the γ-field on the phase diagram contracts to a small region, and with increasing carbon content, initially two-phase (δ + γ)-field expands. Accelerated cooling in the two-phase field, in the absence or narrow range of homogeneous austenite, leads to the transformation of the austenite into martensite and some δ-ferrite remaining (Figure 3a). Unfortunately, a negative effect on mechanical properties is observed – ductile-brittle transition temperature increases and tensile strength decreases with increase δ-ferrite in volume fraction [36,37].

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**Figure 3.** Microstructure of AISI 430F (X12CrMoS17) steel heat-affected zone: (**a**) pseudobinary phase diagram of 0.17C-0.48Si-0.8Mn-0.028P-0.497S-0.26Mo-0.33Ni-0.12Cu-0.05V steel, (**b**) general view, (**c**) coarse-grain heat-affected zone, (**d**) base metal, (**e**) intercritical heat-affected zone (Kalling's and CrO3 etched). **Figure 3.** Microstructure of AISI 430F (X12CrMoS17) steel heat-affected zone: (**a**) pseudobinary phase diagram of 0.17C-0.48Si-0.8Mn-0.028P-0.497S-0.26Mo-0.33Ni-0.12Cu-0.05V steel, (**b**) general view, (**c**) coarse-grain heat-affected zone, (**d**) base metal, (**e**) intercritical heat-affected zone (Kalling's and CrO3 etched). phase field, in the absence or narrow range of homogeneous austenite, leads to the transformation of the austenite into martensite and some δ-ferrite remaining (Figure 3a). Unfortunately, a negative effect on mechanical properties is observed – ductile-brittle transition temperature increases and tensile strength decreases with increase δ-ferrite in volume fraction [36,37].

(polished).

tensile strength decreases with increase δ-ferrite in volume fraction [36,37].

**Figure 4.** SEM microstructure and EDS point analysis of AISI 430F (X12CrMoS17) base metal **Figure 4.** SEM microstructure and EDS point analysis of AISI 430F (X12CrMoS17) base metal (polished).

(polished). Near the fusion line, on both sides, the shape of the inclusions was changed from elongated to spherical, which was caused by high temperature from laser beam welding (Figure 5). The mechanism is shown in Figure 6.

**Figure 4.** SEM microstructure and EDS point analysis of AISI 430F (X12CrMoS17) base metal

mechanism is shown in Figure 6.

mechanism is shown in Figure 6.

Near the fusion line, on both sides, the shape of the inclusions was changed from elongated to

Near the fusion line, on both sides, the shape of the inclusions was changed from elongated to

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**Figure 5.** Microstructure near fusion line on the AISI 430F (X12CrMoS17) base metal side: (**a**) microstructure (polished), (**b**) microstructure (Kalling's etched), (**c**) SEM microstructure and EDS point analysis (polished). **Figure 5.** Microstructure near fusion line on the AISI 430F (X12CrMoS17) base metal side: (**a**) microstructure (polished), (**b**) microstructure (Kalling's etched), (**c**) SEM microstructure and EDS point analysis (polished). **Figure 5.** Microstructure near fusion line on the AISI 430F (X12CrMoS17) base metal side: (**a**) microstructure (polished), (**b**) microstructure (Kalling's etched), (**c**) SEM microstructure and EDS point analysis (polished).

**Figure 6.** Constitutional liquation mechanism of sulfide in partially melted zone. (**a**) before welding; (**b**) during welding; (**c**) after welding. **Figure 6.** Constitutional liquation mechanism of sulfide in partially melted zone. (**a**) before welding; (**b**) during welding; (**c**) after welding. **Figure 6.** Constitutional liquation mechanism of sulfide in partially melted zone. (**a**) before welding; (**b**) during welding; (**c**) after welding.

Sulfides, which were in the high-temperature HAZ, melted with the formation of a liquid film as a result of constitutional liquation. Part of the sulfur-rich liquid was located at grain boundaries in the partially melted zone, while part was located in the weld. At the fusion line, sulfur-rich liquid was not mixed with the weld metal due to the presence of an unmixed zone near the fusion line (Nernst layer). During cooling, the areas with a higher melting point (poorer in impurity) were first crystallized. Figure 7 shows a Scheil Simulation for AISI 430F steel solidification, when the chemical composition corresponds to the tested steel (sulfur mass content was 0.497%) and when the sulfur content was 0%. The solidification temperature of steel with 0.497%S was lower than that of the sulfur-free steel by 394.2 deg. Sulfur-rich liquid is trapped at the grain boundaries and crystallizes in the form of eutectics. Sulfides, which were in the high-temperature HAZ, melted with the formation of a liquid film as a result of constitutional liquation. Part of the sulfur-rich liquid was located at grain boundaries in the partially melted zone, while part was located in the weld. At the fusion line, sulfur-rich liquid was not mixed with the weld metal due to the presence of an unmixed zone near the fusion line (Nernst layer). During cooling, the areas with a higher melting point (poorer in impurity) were first crystallized. Figure 7 shows a Scheil Simulation for AISI 430F steel solidification, when the chemical composition corresponds to the tested steel (sulfur mass content was 0.497%) and when the sulfur content was 0%. The solidification temperature of steel with 0.497%S was lower than that of the sulfur-free steel by 394.2 deg. Sulfur-rich liquid is trapped at the grain boundaries and crystallizes in the form of eutectics.

**Figure 7.** AISI 430F (X12CrMoS17) steel solidification (Scheil Simulation). **Figure 7.** AISI 430F (X12CrMoS17) steel solidification (Scheil Simulation).

In the weld metal, martensite with many spheroidal inclusions was observed (Figure 8). δ-ferrite was not observed in microstructure, which is caused by the presence of nickel, derived from partially melted AISI 304 base metal. With increasing nickel content, the γ-field on the phase diagram expands. Accelerated cooling from homogeneous austenite transforms the austenite into martensite. EDS analysis showed enrichment of inclusions with manganese and sulfur and a similar chromium content to the matrix, which indicated that they are (Cr, Fe, Mn)S inclusions. The small size of the inclusions is responsible for the high iron content, which comes from the matrix. An example of the effective depth of electron penetration in the chemical analysis of small-size MnS inclusion, performed by Monte Carlo Simulation, is presented in Figure 9. Characteristic X-rays were emitted approximately equally from the inclusion and the matrix. In the weld metal, martensite with many spheroidal inclusions was observed (Figure 8). δ-ferrite was not observed in microstructure, which is caused by the presence of nickel, derived from partiallymelted AISI 304 base metal. With increasing nickel content, the γ-field on the phase diagram expands. Accelerated cooling from homogeneous austenite transforms the austenite into martensite. EDSanalysis showed enrichment of inclusions with manganese and sulfur and a similar chromium content to the matrix, which indicated that they are (Cr, Fe, Mn)S inclusions. The small size of the inclusions isresponsible for the high iron content, which comes from the matrix. An example of the effective depth of electron penetration in the chemical analysis of small-size MnS inclusion, performed by Monte CarloSimulation, is presented in Figure 9. Characteristic X-rays were emitted approximately equally from the inclusion and the matrix.

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**Figure 8.** Microstructure and EDS point analysis of weld metal: (**a**) pseudobinary phase diagram of 0.11C-0.7Si-1.9Mn-0.2S-0.4Mo-4.5Ni steel, (**b**), (**c**) microstructure (Kalling's + CrO3 etched), (**d**) SEM microstructure and EDS points analysis (polished). **Figure 8.** Microstructure and EDS point analysis of weld metal: (**a**) pseudobinary phase diagram of 0.11C-0.7Si-1.9Mn-0.2S-0.4Mo-4.5Ni steel, (**b**,**c**) microstructure (Kalling's + CrO3 etched), (**d**) SEM microstructure and EDS points analysis (polished). **Figure 8.** Microstructure and EDS point analysis of weld metal: (**a**) pseudobinary phase diagram of 0.11C-0.7Si-1.9Mn-0.2S-0.4Mo-4.5Ni steel, (**b**), (**c**) microstructure (Kalling's + CrO3 etched), (**d**) SEM microstructure and EDS points analysis (polished).

**Figure 9.** Monte Carlo Simulation of electron trajectory in MnS inclusion and AISI 430F (X12CrMoS17) matrix. **Figure 9.** Monte Carlo Simulation of electron trajectory in MnS inclusion and AISI 430F (X12CrMoS17) matrix. **Figure 9.** Monte Carlo Simulation of electron trajectory in MnS inclusion and AISI 430F (X12CrMoS17) matrix.

Base metal of AISI 304 steel (Figure 10a,b) was characterized by austenitic microstructure with banded δ-ferrite. The orientation of the δ-ferrite and a large content of twins indicate a mechanical worked delivery condition. In high-temperature HAZ (Figure 10c,d), disappearance of twins due to the recrystallization was observed, which significantly reduces strength properties [38]. Base metal of AISI 304 steel (Figure 10a,b) was characterized by austenitic microstructure with banded δ-ferrite. The orientation of the δ-ferrite and a large content of twins indicate a mechanical worked delivery condition. In high-temperature HAZ (Figure 10c,d), disappearance of twins due to the recrystallization was observed, which significantly reduces strength properties [38]. Base metal of AISI 304 steel (Figure 10a,b) was characterized by austenitic microstructure with banded δ-ferrite. The orientation of the δ-ferrite and a large content of twins indicate a mechanical worked delivery condition. In high-temperature HAZ (Figure 10c,d), disappearance of twins due to the recrystallization was observed, which significantly reduces strength properties [38].

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**Figure 10.** Microstructure of AISI 304 (X5CrNi18-10) steel heat-affected zone: (**a**) pseudobinary phase diagram of 0.05C-0.59Si-1.95Mn-0.009P-0.003S-0.04Mo-8.02Ni-0.05Cu steel, (**b**), (**c**) base metal, (**d**), (**e**) heat-affected zone (Kalling's + CrO3 etched). **Figure 10.** Microstructure of AISI 304 (X5CrNi18-10) steel heat-affected zone: (**a**) pseudobinary phase diagram of 0.05C-0.59Si-1.95Mn-0.009P-0.003S-0.04Mo-8.02Ni-0.05Cu steel, (**b**,**c**) base metal, (**d**,**e**) heat-affected zone (Kalling's + CrO3 etched).

Comparison of the expected weld structure with the obtained results of the EDS analysis was performed with the Schaeffler diagram (Figure 11). OES analysis results of base metals, average values determined assuming of 50% dilution of both material and EDS analysis results of weld metal are presented in Table 3. In the case of AISI 430F steel, the predicted structure is martensite with approx. 24% ferrite, which essentially coincides with the obtained microstructure in the HAZ. Base metal was heat treated before welding; therefore, the structure does not correspond to that of the Schaeffler diagram. The structure of the AISI 304 steel according to the diagram is composed of austenite with approx. 8% ferrite and a small amount of martensite, which correspond to the observed microstructure. In the case of the weld, a difference between the average and measured chemical composition was identified (Table 3). Chemical composition of the weld obtained in the EDS analysis indicates that dilution of AISI 304 steel in the weld was 65% and AISI 430F was 35%. Non-axial arrangement of the laser beam in relation to the contact point of both welded materials and the difference in melting temperature and thermal conductivity coefficient values were the reasons for uneven melting. Regardless of the degree of dilution, the microstructure should consist of martensite, residual austenite and approx. 13% ferrite. Comparison of the expected weld structure with the obtained results of the EDS analysis was performed with the Schaeffler diagram (Figure 11). OES analysis results of base metals, average values determined assuming of 50% dilution of both material and EDS analysis results of weld metal are presented in Table 3. In the case of AISI 430F steel, the predicted structure is martensite with approx. 24% ferrite, which essentially coincides with the obtained microstructure in the HAZ. Base metal was heat treated before welding; therefore, the structure does not correspond to that of the Schaeffler diagram. The structure of the AISI 304 steel according to the diagram is composed of austenite with approx. 8% ferrite and a small amount of martensite, which correspond to the observed microstructure. In the case of the weld, a difference between the average and measured chemical composition was identified (Table 3). Chemical composition of the weld obtained in the EDS analysis indicates that dilution of AISI 304 steel in the weld was 65% and AISI 430F was 35%. Non-axial arrangement of the laser beam in relation to the contact point of both welded materials and the difference in melting temperature and thermal conductivity coefficient values were the reasons for uneven melting. Regardless of the degree of dilution, the microstructure should consist of martensite, residual austenite and approx. 13% ferrite.

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**Figure 11.** Schaeffler constitutional diagram: (**a**) general view, (**b**) enlarged view. **Figure 11.** Schaeffler constitutional diagram: (**a**) general view, (**b**) enlarged view.

**Table 3.** Chemical composition of base metals (OES) and weld metal (arithmetic mean of the chemical composition of base metals and EDS analysis). **Table 3.** Chemical composition of base metals (OES) and weld metal (arithmetic mean of the chemical composition of base metals and EDS analysis).

1 arithmetic mean of the chemical composition of base metals, 2 EDS analysis. 1 arithmetic mean of the chemical composition of base metals, 2 EDS analysis.

The hardness distribution map on the cross section of the joint is shown in Figure 12a. Hardness of the AISI 430F base metal was the lowest in the welded joint and amounted to 178–205 HV0.3. In the HAZ an increase in hardness to 417 HV0.3 was noted. On the AISI 304 steel side, the hardness was 259–333 HV0.3, which decreased to 191 HV0.3 in HAZ, reaching the hardness of the AISI 430F steel in the delivery condition. In the weld metal, hardness ranged from 184 to 416 HV0.3, which corresponds to the lowest and highest hardness in the other zones of the joint. The large difference in the hardness of the weld was caused by chemical segregation, shown in Figure 12b. EDS analyses were performed in the areas of 192 × 192 μm (0.037 mm2), where the centers of indentation and analyzed areas were a common point. The zones with the highest hardness coincide with the areas with decreased chromium and nickel contents, i.e., the main components of chromium and nickel equivalents (RCr and RNi) decreased in these areas (Figure 12c). The determination of distribution of carbon in the weld metal using EDS analysis was not possible. When this distribution was simplified to be homogeneous, as the nickel equivalent value was decreased, the volume fractions of martensite and ferrite increased at the cost of austenite, and the hardness in the weld increased (Figure 12d). The hardness distribution map on the cross section of the joint is shown in Figure 12a. Hardness of the AISI 430F base metal was the lowest in the welded joint and amounted to 178–205 HV0.3. In the HAZ an increase in hardness to 417 HV0.3 was noted. On the AISI 304 steel side, the hardness was 259–333 HV0.3, which decreased to 191 HV0.3 in HAZ, reaching the hardness of the AISI 430F steel in the delivery condition. In the weld metal, hardness ranged from 184 to 416 HV0.3, which corresponds to the lowest and highest hardness in the other zones of the joint. The large difference in the hardness of the weld was caused by chemical segregation, shown in Figure 12b. EDS analyses were performed in the areas of 192 × 192 µm (0.037 mm2 ), where the centers of indentation and analyzed areas were a common point. The zones with the highest hardness coincide with the areas with decreased chromium and nickel contents, i.e., the main components of chromium and nickel equivalents (RCr and RNi) decreased in these areas (Figure 12c). The determination of distribution of carbon in the weld metal using EDS analysis was not possible. When this distribution was simplified to be homogeneous, as the nickel equivalent value was decreased, the volume fractions of martensite and ferrite increased at the cost of austenite, and the hardness in the weld increased (Figure 12d).

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**Figure 12.** Hardness map of the joint and chemical composition distribution in weld metal. (**a**) hardness map; (**b**) chemical composition map; (**c**) chromium and nickel equivalents map; (**d**) hardness distribution depending on the chromium and nickel equivalents. **Figure 12.** Hardness map of the joint and chemical composition distribution in weld metal. (**a**) hardness map; (**b**) chemical composition map; (**c**) chromium and nickel equivalents map; (**d**) hardness distribution depending on the chromium and nickel equivalents.