The influence of tempering temperature on the microstructure of powder metallurgy high-speed steels (PM HSSs) PM20 is investigated by X-ray diffraction, electron backscattering diffraction, and transmission electron microscopy. With the increasing of tempering temperature, the ratio of low angle grain boundaries decreases, while the volume fraction and size of M 6 C and VC carbides increase. The wear resistance of PM20 with different tempering temperatures is studied by reciprocating ball-on-flat methods. The wear properties of PM20 decrease gradually with the increasing of tempering temperature. The variation of wear properties is explained by the characteristic of the martensite matrix, carbides, and the misorientation angle of boundaries. All samples present a complex wear mechanism of abrasive wear and oxidation wear.
The microstructure of a powder metallurgical high‐speed steel (PM HSS) after sliding wear is investigated by using electron backscattering diffraction (EBSD) and transmission electron microscope (TEM). Part of martensite blocks become coarsened as the fine blocks can still be seen after sliding wear. The texture, nanolamellar structure, and twin martensite are observed, which suggests that grain rotation and grain boundary migration are driven by plastic deformation and are the main factors for grain growth. However, grain rotation and grain boundary migration are also blocked by carbides and alloy elements segregation, resulting in discontinuous grain growth.
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