Characterization and comparison of white layer by hard turning versus grinding

Compared with grinding, hard turning has the potential to make a variety of precision components of superior surface integrity, such as bearings, gears, cams, shafts, tools, dies, etc., while reducing investment, increasing production rate, and eliminating environmental pollution. Despite its spectrum of advantages over cost intensive grinding process, industrial realization of hard turning still remains in incipient stage. The low industrial acceptance of hard turning may be attributed to uncertainty related to surface quality especially for the white layer which is a key factor of surface integrity and thus product performance.

A comparative study has been conducted to solve the current problems. Hard turning and grinding AISI 52100 (62 to 64 HRC) steel were designed and conducted to generate the white layer. Then, white layer induced by hard tuning and grinding were characterized and compared in six aspects: (1) Surface structure by optical microscope; (2) Hardness by microhardness tester; (3) Microstructure by scanning electron microscopy (SEM); (4) Chemical composition by X-ray photo spectroscopy (XPS); (5) Retained austenite phase by X-ray diffraction; (6) Crystal defects and microstructure by Transmission Electron Microscopy (TEM).