Hard coating by plasma-assisted CVD on plasma nitrided stellite

To maximize an abrasive-wear-resistant function of stellite 6B, a cobalt-base superalloy, a duplex treatment combined with diffusion-dominated plasma nitriding of the substrate and a multilayer coating system of titanium compounds TiN-Ti(C, N)-TiC by plasma-assisted CVD has been designed and developed. Its treatment process has been optimized to impart both smoothness on the top surface of the coating system and a very low level of chlorine in the multilayers. It has also been optimized to be a continuous process at a constant temperature in the same unit simply by changing the flow of reactive and inactive gases, plasma power (gradually) and treatment time, responding to an individual step of the combined process. This developed duplex treatment at 650 degrees C was well applied to the surface of a stellite 6B workpiece that had been under severe abrasive wear. (C) 1998 Elsevier Science S.A.