Orientation dependence of the wear resistance in the Co-Cr-Mo single crystal

This is the report clarifying the orientation dependence of the wear behavior of Co-Cr-Mo alloy. The wear resistance of the Co-Cr-Mo alloy with face-centered cubic (fcc) structure was found to be higher on the planes in order of {110}, {001} and {111}. Quantitatively, the wear resistance on {110} is 1.5 times larger than that on {111}. The tendency showed in coincident with the orientation dependence of the surface hardness, as empirically suggested. However, we additionally found in the observation of the worn surface in the fcc-single crystals that the volume fraction of the hexagonal close-packed (hcp)-phase, which was formed as the strain-induced martensite during the wear test, was larger in the same order of the wear resistance. The variation in formation frequency of the hcp-phase during the wear test can be explained by focusing on the Schmid factor along the resultant direction of the applied stress and the friction stress. On the {111} surface where the Schmid factor for the strain-induced epsilon-martensite formation is small, homogeneous deformation microstructure covered by it was not developed even after long-time wear, resulting in lower wear resistance. The results strongly suggest that not only the hardness, but the distribution of the epsilon-martensite is important to control the wear behavior of the Co-Cr alloys with the extremely low stacking fault energy, and it can be achieved by the crystal orientation control in the gamma-phase.

Automated summary

The research clarifies the orientation dependence of the wear behavior of Co-Cr-Mo alloy, showing higher wear resistance on {110} planes compared to {111}. Additionally, the formation of the hexagonal close-packed (hcp) phase during wear is influenced by the applied stress direction. The study suggests that controlling the distribution of epsilon-martensite is crucial in determining the wear behavior of Co-Cr alloys.