White etching cracks (WECs), first reported in 1996, are cracks that can form in the microstructure of bearing steel, leading to the development of a network of branched white cracks. They are usually observed in bearings that have failed due to rolling contact fatigue or accelerated rolling contact fatigue. These cracks can significantly shorten the reliability and operating life of bearings, both in the wind power industry and in several industrial applications.
The exact cause of WECs and their significance in rolling bearing failures have been the subject of much research and discussion. Ultimately, the formation of WECs appears to be influenced by a complex interplay between material, mechanical, and chemical factors, including hydrogen embrittlement, high stresses from sliding contact, inclusions, electrical currents, and  temperature. They all also have all been identified as potential drivers of WECs.