Research on Surface Hardening and Dimensional Stabilisation Process of High-speed Precision Bearings
The microstructure characteristics,hardening layer gradient and residual austenite content of GCr15 bearing steel under different heat treatment processes were analyzed and studied using optical mi-croscopy (OM),microhardness tester and X-ray diffraction (XRD).The results showed that the technical requirements for bearing parts with surface hardness greater than 63 HRC,the residual austenite content in the matrix less than 3％ and the residual austenite content on the surface about 6％ could be achieved through carbonitriding quenching,cold treatment at-70 ℃ for 2 h and tempering at 220 ℃ for 4 h,and ensured the dimensional accuracy of the parts while avoiding the low contact fatigue life of the bearings due to the low residual austenite content.By adding trace amounts of strong carbide alloying elements such as Mo and V to the raw materials,and undergoing two quenching processes of martensitic quenching and car-bonitriding,the average grain size of the matrix was refined from grade 8 to more than grade 10.
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