Tribological and microstructural studies of oxygen-implanted ferrite and austenite

Ferrite (pure α-Fe) and austenite (AISI 304 stainless steel) discs were implanted to doses ranging from 1x1017 to 1x1018 O2 cm-2 at temperatures ranging from 90 to 500degC and tested using an oscillating pin-on-disc wear tester. Moessbauer spectroscopy, X-ray diffraction and Auger electron spectroscopy were used to characterize the microstructures and compositions of the implanted layers. Although oxygen implantation reduces the wear rates of both steel constituents at all implantation doses and temperatures, the lowest wear rates are observed in the α-Fe implanted at the lower doses and temperatures and in the stainless steel implanted at elevated temperatures. Ranked from most to least wear resistant, the oxides observed in ferrite are FeO, Fe2O3 and Fe3O4. When discs of austenite are implanted, hematite-like oxide is formed at all temperatures and a magnetite-like oxide begins to appear in addition at elevated temperatures (500degC at 4x1017 O2 cm-2 and 430degC at 1x1018 O2 cm-2). The hematite-like oxide formed when 4x1017 O2 cm-2 is implanted at 400degC induces the greatest load for the transition from mild to severe adhesive wear (approximately 300 times the load for unimplanted discs). (orig.)