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Grind-hardening machining is not only a complex process coupling mechanical,dynamical and thermal effects,but a process containing distinct changes of microstructure and property of surface layer on the workpiece.Under the defined experimental conditions,the hardened layer depth (HLD) increases when grinding speed/depth increases,or the feed speed decreases.Based on experimental results,an empirical formula is constituted to describe the relation between HLD and grinding parameter of grind-hardening layer,and the multi-parametric optimization is conducted.There are a variety of factors influencing the hardened layer depth.The intension and moving speed of the heat source in the contact zone between grinding wheel and workpiece are two key factors to influence the HLD.A commercial FEM software package is used to simulate the grind-hardening process.The distribution and variation characteristics of the temperature and microstructure in the grinding surface layer are obtained.Because of high grinding temperature and large temperature gradient,the entirely austenized zone of the workpiece surface layer is relatively deep and the partially austenized zone is narrow.The overcooling austenite directly enters the martensitic transformation zone for the intense self-cooling effects of the workpiece basal body,making the martensite distribution inherit the austenite distribution characteristics so as to form the special microstructure and properties of the grind-hardened layer finally.