Effect of cryogenic burnishing on surface integrity modifications of Co-Cr-Mo biomedical alloy

Severe plastic deformation (SPD) processes have been used to modify the surface integrity properties of many materials by generating ultrafine or even nanometer-sized grains in the surface and subsurface region. These fine grained materials created by SPD and dynamic recrystallization in a thin layer near the surface usually have higher hardness and frequently exhibit enhanced mechanical properties (wear resistance, corrosion resistance, fatigue life, etc.). Cryogenic burnishing, a SPD process, was used to improve several surface integrity parameters of a Co-Cr-Mo biomedical alloy. Application of liquid nitrogen during the burnishing process significantly suppressed the temperature rise within and outside the nitrogen application zone. Better surface finish, high hardness value, thick burnishing-influenced surface layer, and significant grain refinement were simultaneously achieved with the application of cryogenic cooling. Current results show that cryogenic burnishing can be an effective processing method for modifying the studied surface integrity properties of Co-Cr-Mo biomedical alloy.