COMPARATIVE ASSESSMENT OF SURFACE ROUGHNESS AND MICROSTRUCTURE PRODUCED IN WHIRLWIND MILLING OF BEARING STEEL

摘要

The surface roughness and deformation microstructure of the GCr_(15) subjected to whirlwind milling (WM) were characterized. The machined surface roughness was modeled for predicting, and effects of cutting parameters on surface roughness were studied. Microstructure evolution was investigated using electron backscatter diffraction (EBSD).The microstructure in the top surface evolved into sub-boundaries and highly misoriented grain boundaries, and consisted of a mixture of elongated subgrains. The average size was 167 × 10~2 nm~2 in WM zone, which was less than 194 × 10~2 nm~2 in the non-WM zone. The presence of slip lines within the deformed grains was clearly noticeable. The predicted average surface roughness was evidently smaller than the experimental result, but the same conclusion was determined in in the effects of cutting depths and cutting speeds on surface roughness. The variation tendencies of hardness profiles were initially proved to be almost consistent to that of user-defined boundaries average misorientation (BsAM) calculated from the data detected by EBSD. The proposed models were validated by comparing the predicted results with experimental data.