Effects of Ion Implantation on Cavitation Erosion of a Cobalt Based Metal/Carbide Alloy

摘要

The goal of this work was to characterize the cavitation erosion wear mechanisms in a cobalt based superalloy and to investigate how these could be altered by high fluence titanium and nitrogen implantations. Both titanium and nickel implantations significantly improved the cavitation erosion resistance of the alloy, primarily through implantation effects in the cobalt rich matrix phase. The titanium implanted samples showed the highest erosion resistances, as a result of the microstructural changes produced in the alloy during implantation. Namely, a carburized surface layer was formed, with an amorphous matrix phase and recrystallized carbides. A corresponding toughening of the matrix phase and decrease in the elastic modulus difference between matrix and carbide phases can account for the observed increased erosion resistance of this phase and enhanced carbide-matrix cohesion. Nitrogen implantation stabilized the metastable fcc matrix phase of the alloy... (i.e., inhibited stress induced martensitic facc to hcp transformations in the cobalt rich phase) with consequent prolonged matrix phase ductility and decreased carbide-matrix debonding during cavitation erosion.