TRANSITIONS OF MICROSCOPIC WEAR MODE OF SILICON-CARBIDE COATINGS BY CHEMICAL-VAPOR-DEPOSITION DURING REPEATED SLIDING OBSERVED IN A SCANNING ELECTRON-MICROSCOPE TRIBOSYSTEM

The purpose of this investigation is to analyze microscopic wear mecha nisms of silicon carbide coatings by chemical vapor deposition (CVD). For this purpose, the wear processes during one hundred sliding cycles were observed successively in a scanning electron microscope (SEM) tr ibosystem. The results were compared with those of uncoated silicon ca rbide. The following results were obtained. (1) Wear modes are classif ied into four, they are ploughing, powder formation, crack formation a nd flake formation. These wear modes except for ploughing are mainly c aused by surface crack propagation. (2) Silicon carbide coatings showe d higher wear resistance than uncoated silicon carbide, because there are less initial surface cracks in the silicon carbide coatings. (3) T he condition for wear mode transition can be explained theoretically b y using the parameters of severity of contact, S-c, S-c, and the fric tion coefficient mu, where S-c = P-max(R(max))(1/2)/K-1c and S-c() = H-v(R(max))(1/2)/K-1c.