ADHESION IMPROVEMENTS IN SILICON-CARBIDE DEPOSITED BY PLASMA ENHANCED CHEMICAL VAPOR-DEPOSITION

The ability to deposit a hard, adherent, wear resistant, inert thin coating on complex geometries at temperatures at and below 350-degrees-C will find application both in the cutting industry and where coatings on cheaper substrates can replace expensive bulk material. This study describes the deposition of silicon carbide coatings from a conventional plasma-enhanced chemical vapour deposition reactor. The deposition was conducted at 350-degrees-C from source gases of SiH4, NH3, C2H4, N2, and H2 in a 300 kHz high frequency plasma. A variety of substrates including M2 high speed steel, tool steel and cemented carbides were coated. The coatings were characterized in terms of their mechanical properties, tribological properties and composition, especially at the interfaces. The ex situ and in situ pretreatment of the substrates using different etching processes was found to be of paramount importance in achieving good adhesion. The effects which interface layers have on the change in adhesion of silicon carbide to the substrate were also addressed.