Producing high quality hardened parts using sequential hard turning and ball burnishing operations

This paper presents a novel sequential process which incorporates optionally CBN turning operations with (CHT) or without (HT) cryogenic pre-cooling of the workpiece and ball burnishing (B) operations. The main hypothesis tested concerns the fact that cryogenic pre-cooling slightly deteriorates surface finish but at the same time it enhances the mechanical and service properties of the subsurface layer without white layer. Moreover, it indicates how this complex process (cryogenic pre-cooling, hard turning and ball burnishing) should be performed to obtain satisfactory surface integrity and service properties. Investigations include 2D and 3D surface roughness, microstructure alterations by means of SEM/BSE techniques and microhardness distribution. The geometrical, mechanical and physical improvements of surface layer properties were revealed.