Research On The Effect Of Cryogenic And Surface Treatment On Wear Property Of High Speed Steel

High speed steel tool plays an important role in improving the efficiency of processing, especially as an indispensable material in the manufacturing of complex and precision tools. At present about 95% of the tapping and sawing tool use high speed steel. But there existed a serious problem in the domestic high-speed steel tool material. That is the short life and the low reliability. With the enhancement of the material processed, high-speed steel tool life is lower and lower. The heat treatment is an important way to improve the mechanical properties and wear resistance of high speed steel material. Although the literature of this field is limited, there is still controversial in cryogenic treatment to improve the efficiency of life assessment of high speed steel cutter cryogenic treatment as the extension of heat treatment can improve the performance and wear resistance of the material. The research and application of passivation technology in the process of manufacturing tool is very extensive, the life of the tool could be effectively enhanced by changing the geometric dimension of the tool cutting edge. However, the research of passivation's effect on the surface properties of the material is very little.The research sample is W6Mo5Cr4V2 in the paper. According to the conventional experimental design method, considering such three factors as the cryogenic, heat treatment and passivation process, systematic experiment research process was made to improve wear resistance, hardness and reduce the residual stress of high-speed steel. The main research contents are as follows:(1) The systematic process was developed, contains three factors for the variables of cryogenic treatment process: cooling rate, cryogenic temperature and holding time; two factors for the variable tempering treatment process: tempering temperature and tempering times and passivation process;(2) Cryogenic temperature, holding time, cooling rate, number of tempering, tempering temperature of different cryogenic and tempering treatment were explored to reduce the residual stress of the surface. The results show that the improved cooling and tempering process could reduce the residual stress on the surface of the material, when the cooling rate selected 1?/min, tempering temperature selected 440?, tempering times selected three times, the residual stress is minimum;(3) The effect of different cryogenic treatment,tempering treatment and passivation process on the wear resistance of material was achieved by wear test of the specimen experiencing different treatments: Cryogenic and tempering process could enhance the wear resistance and hardness of the work piece, when cooling rate selected 2?/min, tempering temperature selected 440?, tempering times selected three times, anti-wear has best performance, hardness is the best. And surface passivation technology could improve the quality of material surface, improve initial abrasion wear, reduce vibration, and improve wear resistance;(4) The samples experiencing wear test was gained to explore the microstructure and morphology of wear scar, and the reason of the change of wear resistance, which provided the basis for the design of the following process route. Observations indicate that cryogenic treatment and tempering process could improve the size, the precipitation amount and the distribution of carbides, which is the main reason for improving wear resistance. Surface passivation treatment process could make material surface precipitate large amount of carbonaceous material, which has a certain degree of lubrication, so as to reduce the vibration, and improve the wear resistance of materials.The conventional test design method was applied in this paper, and system experiment research process was developed from the cryogenic, heat treatment and surface passivation process three aspects, mainly to improve high-speed steel material wear resistance, hardness and reduce the residual stress. The influence of cryogenic(cryogenic temperature, holding time, cooling rate), tempering(tempering times, tempering temperature) and surface passivation treatment on wear resistance has been gotten, and the reason of it has been analyzed from the micro level, providing reference for the further study of cryogenic treatment and surface passivation technology.