HARD COATING BY PLASMA-ASSISTED CVD ON PLASMA-NITRIDED STELLITE

To maximize an abrasive-wear-resistant function of stellite 6B, a coba lt-base superalloy, a duplex treatment combined with diffusion-dominat ed plasma nitriding of the substrate and a multilayer coating system o f titanium compounds TiN-Ti(C, N)-TiC by plasma-assisted CVD has been designed and developed. Its treatment process has been optimized to im part both smoothness on the top surface of the coating system and a ve ry low level of chlorine in the multilayers. It has also been optimize d to be a continuous process at a constant temperature in the same uni t simply by changing the flow of reactive and inactive gases, plasma p ower (gradually) and treatment time, responding to an individual step of the combined process. This developed duplex treatment at 650 degree s C was well applied to the surface of a stellite 6B workpiece that ha d been under severe abrasive wear. (C) 1998 Elsevier Science S.A.