Effects of nitrogen implantation on the tribology and microstructure of cobalt-based systems

Abstract

High fluence nitrogen implantation improved the cavitation erosion resistance of a cobalt-based superalloy (Stoody 3), primarily because of implantation effects in the cobalt-based matrix phase. As shown by X-ray diffraction examinations of eroded alloy surfaces, the metastable face-centered cubic (f.c.c.) matrix phase is stabilized by implantation. Prolonged matrix phase ductility and decreased carbide-matrix debonding were the results of the reduced incidence of stress-induced f.c.c. to hexagonal close packed (h.c.p.) transformations in the implanted surfaces during cavitation. The cavitation erosion resistance of a 6wt.%Co-WC cemented carbide also improved with implantation, again because of increased durability of the matrix phase.