The study on contact failure experiment of nitridedand duplex treated 32Cr2NoVa

摘要

Deposition of TiN onto nitrided substrate, which called duplex treatment, can provide working surface with high wear resistance. In this paper, TiN layer were selected to deposit onto the 32Cr2MoVA by ion plating to investigate the influence of duplex treatment on the wear resistance and contact failure properties. After rolling contact fatigue experiment, the S-N curves of nitrided and duplex treated 32Cr2MoV were drawn as well as the surface morphology and microstructure of the cross section of the coated and uncoated 32Cr2MoVA were observed by SEM and optical microscope. The results showed that lifetime of coated-TiN 32Cr2MoV were greater than that of nitrided 32Cr2MoVA at the low stress level, which demonstrated that TiN could provide the sub-surface protection. The pitting on the surface of duplex treated samples was shallower than that of nitrided samples and the surface of duplex treated samples was smoother than that of nitrided samples. The microstructure on TiN-coated superficial case was finer and content of white nitrides were higher than that of nitrided. Thus, the duplex structure of TiN film and nitrided case could insure higher hardness and proper hardness distribution in 0.2mm depth than nitrided structure. It is concluded that duplex treatment is an effective way to increase the surface contact fatigue strength.