Effect of cryogenic tempering treatment on hardness of pick tip of roadheader

YG8 cemented carbide was selected as the pick tipping material of the roadheader.For the purpose of improving the Vickers hardness of YG8 cemented carbide, the parameters of cryogenic tempering were optimized by orthogonal design method, and the effects of different cryogenic temperature, cryogenic speed, cryogenic time, tempering temperature and tempering times on the Vickers hardness of YG8 cemented carbide was obtained by the range method.The results show that the effect of cryogenictempering on the micro Vickers hardness of YG8 cemented carbide is -15.96～53.02 HV1, and the maximum increase is 4.35%.The order of influence of cryogenic tempering process parameters on Vickers hardness of YG8 cemented carbide is tempering times> cryogenic time> cryogenic speed>cryogenic temperature>tempering temperature,and the optimum process parameter combination is cryogenic speed of 3 ℃/min, cryogenic temperature -160 ℃, cryogenic time 12 h, tempering temperature 150 ℃, tempering times of 4.Cryogenic treatment can promote dense shrinkage of the binder phase, which contributes to the improvement of the hardness of YG8 cemented carbide.