Influence of the Grinding Pass on Microstructure and its Uniformity of the Grind-Hardened Layer

On the basis of the surface grind-hardening experiment, the influence of grinding pass on the microstructure and its uniformity of the grind-hardened layer of 65Mn steel were studied using optical microscope, scanning electron microscope, and digital microhardness tester in detail. The results show that the grind-hardened layer generated by two-passes grinding has better uniformity compare with one-pass grinding along the length. Under the conditions of this experiment, grind-hardened layer generated by one-pass grinding has part unhardened region, and grinding pass has little remarkable effect upon the delamination of the macrostructure, the microstructure and its microhardness value of the hardened layer. The hardened layer comprises completely hardened zone and transition zone, and the completely hardened zone whose microhardness is about 780HV0.5 is of fine lathe martensites, residual austenite and a few carbides. The grind-hardened layer uniformity can be observably enhanced when two-passes grinding is adopted.