Plasma duplex treatment of stellite

Despite their excellent tribological properties, the lifetime of stellites in some applications in metallurgical and mechanical engineering is not suf ficient. This study describes the development of a duplex treatment for ste llite 6B, which consists of either plasma nitriding (PN) or plasma nitrocar burizing (PNC), followed by the deposition of boron-containing hard coating s (TiBN or TiB2). The influence of the process parameters and the gas compo sition was investigated. Compositional and structural analysis was performe d by: profilometry; XRD; SEM; WDS; and GDOS. Knoop hardness measurements, s cratch tests, pin-on-disk tests and wear tests by ball cratering were deter mined in order to describe the mechanical properties. It is shown that plas ma duplex treatment combines the advantages of both separate process steps. Case hardening during diffusion treatment offers a mechanical support to t he coating, which exhibits a lower coefficient of friction than the diffusi on-treated surface. The optimal combination consists of PNC, at high plasma energy, and a boron rich TiBN coating. (C) 2001 Elsevier Science BN. All r ights reserved.