不同组织高铬白口铸铁低速重载滑动干摩擦磨损行为

摘要

对不同化学成分的高铬白口铸铁进行不同热处理,通过低速重载滑动干摩擦磨损试验研究了高铬白口铸铁的磨损率和摩擦因数与摩擦功率密度、正压应力、碳化物类型和基体组织的关系,并探讨了低速重载条件下高铬白口铸铁的滑动干摩擦磨损机理.结果表明:高铬白口铸铁的摩擦因数与碳化物相类型和正压应力有关,而与基体组织无关;磨损率与基体组织类型、碳化物相类型和摩擦功率密度均有关;在低速重载滑动干摩擦磨损过程中,铸铁的组织由摩擦面至内部依次为摩擦层、流变层、应变带、不变区等4个区域;摩擦层中原始基体组织遇到严重破坏,与破碎碳化物充分混合;流变层中固相塑性流变的黏滞阻力增大,导致裂缝、空洞形成,最终产生疲劳剥落;应变带中碳化物相因基体组织的塑性变形而发生弯曲或断裂.%High chromium white cast irons with different chemical compositions were heat treated by different ways.The relationship of friction coefficient and wear rate of high chromium white cast irons with friction power intensity,positive pressure stress,carbide phase and matrix structure were investigated by dry sliding friction and wear tests under low speed and heavy load.The mechanism of dry sliding friction and wear of high chromium white cast iron under low speed and heavy load was discussed.The results indicate that the friction coefficient of high chromium white cast iron was related to the type of carbide phase and positive pressure stress, but was not related to the matrix structure.The wear rate was concerned with the type of matrix structure,the type of carbide phase and friction power intensity.The microstructure of the cast iron was consisted of friction layer, rheological layer,strain band and stability region in sequence from friction surface to inside during dry sliding friction and wear test.The original matrix structure was severely damaged and fully mixed with broken carbide in the friction layer.The viscous resistance of solid phase plastic flow increased in the rheological layer resulted in the formation of crevices and caves,and fatigue flake occurred finally.The carbides in the strain band bent or was ruptured due to plastic deformation of matrix structure.