Formation of a nanocrystalline recrystallized layer during microabrasive wear of a cobalt-chromium based alloy (Co-30Cr-19Fe)

The tribological behavior of a cast cobalt-chromium alloy, during microabrasion testing, was investigated. The alloy's microstructure contains coarse grains of fcc cobalt rich dendrites, interdendritic segregations and almost no precipitates. The tests were done using a 0.1 g/cm3 Al2O3/distilled water slurry, 0.3 N applied load and 20 rpm rotational speed. Two-body abrasion (grooving wear) was the dominating wear micromechanism. A severely deformed nanocrystalline layer containing random oriented ∼20 nm grains was observed, immediately below the worn surface. Finite element modeling of a single Al2O3 particle scratching the Co-Cr alloy surface showed that severe plastic deformation occurs in a region 1-2 μm beneath the worn surface, giving rise to the observed nanocrystalline layer.