Coating cylinder bores with ultra thin solid lubricant phase
Cylinder bores (16) are coated by preparing the cylinder bore surface to expose fresh metal free of contamination, generating through a nozzle (13) from a highly pressurised supply of emulsion a hollow conical spray consisting of fine mist droplets (38) of a solid lubricant emulsion, the conical spray having an effective base with a diameter greater than the diameter of the cylinder bore, and moving by means (15, 20, 21) the apex of the conical spray (28) along the axis of the bore at a uniform speed to deposit a coating of the emulsion on the interior of such cylinder bore in a thickness of no greater than 30 microns. The lubricant emulsion may consist of a mixture of molybdenum disulfide, boron nitride and graphite in a thermoset or thermoplastic polymer resin base. The nozzle may have diverging and converging conical surface sections (32, 33) to induce the flow of emulsion to exit from the nozzle with a hollow interior.