Surface Engineering with Lasers: Application to Co Based Materials

Abstract

Electron Inicroscopy, mechanical hardness measurements, and wear experiments have been carried out on316 stainless steel laser coated with Co based Stellite alloys. It has been found that with optimum laser parameters a poreless coating with a hardness of 11·3 GPa can be attained. Detailed analysis indicates that solid solution hardening by Wand Cr, dislocation–dislocation interactions, and dispersion hardening owing to the metal carbides and the C0₃ W precipitates are responsible for the high hardness. In accordance with theoretical predictions, cuttingof the DO₁₉ ordered C0₃W precipitates was not observed. All these microstructural features contribute to the mechanical properties, on the basis of which the hardness can be successfully explained. An ilnportant parameter which influences these mechanical properties is the low dilution of the coating by the substrate. It is this aspect, together with the well defined and controllable processing parameters, which makes laser coating of powders superior to other deposition techniques for depositing Stellite layers.