选择性激光相变40Cr钢摩擦磨损性能研究

Study on the friction and wear properties of 40Cr steel by selective laser transformation

为了解决40Cr钢零部件表面磨损问题,结合表面织构理论,采用激光相变硬化工艺制备分布规则的不同形状(圆形、条状)软硬耦合表面。通过扫描电镜、X射线衍射、摩擦磨损实验和超景深显微镜分别分析相变区微观组织、物相,评估表面抗磨损性能、磨损表面形貌。结果表明,圆形相变区截面硬度高于条状,平均介于(720±3)HV_(0.1),且淬硬层较深;相变后生成马氏体、Cr_(7)C_(3)、Fe_(7)C_(3);对比40Cr钢未处理表面与软硬耦合表面摩擦系数,软硬耦合表面摩擦系数均低于0.5且波动小,具备好的摩擦稳定性;磨损表面损伤小,源于磨损过程硬质相能够阻碍磨屑运动、减少表面损伤,软相区可以缓存能量和碎屑,软相区以梨削、粘着损伤为主,硬相区以小点蚀坑为主,900W圆形软硬耦合表面减磨耐磨效果最好;塑韧好、表面规律分布、一定比例(50%)硬质相能够有效提升和改善材料工作表面抗磨损性能,改善对磨副接触表面,进而能够稳定摩擦系数。该研究可为改善40Cr零部件表面磨损提供参考。

To solve the surface wear problem of 40Cr steel parts,incorporated with the theory of surface texture,laser phase transformation hardening technology was applied to preparate various shapes(spot and striation)of hard-soft coupling surfaces with regular distribution.Scanning electron microscopy,X-ray diffraction,friction and wear machine and ultra-depth of field microscopy were adopted to analyze the microstructure,physical phase,anti-wear performance,and wear surface morphology of the phase transformation zone.the results show that the cross-section hardness of the spot phase transformation zone is higher than the striation,with the average of(720±3)HV_(0.1),and the hardening layer is deeper.Martensite,Cr_(7)C_(3),and Fe_(7)C_(3)are generated after phase transformation.By comparing the friction coefficient between the untreated surface and the hard-soft coupling surface of 40Cr steel,the friction coefficient of the hard-soft coupling surface is inferior to 0.5 and its fluctuation is smaller which demonstrates great friction stability.In addition,the wear surface damage of the hard-soft coupling surface is small,and the reason of this is that the hard phase could resist the deformation while the soft phase could release the stress concentration and the accumulation of plastic deformations.The soft phase field is mainly pear peeling and adhesion damage,and the hard phase area is mainly small pitting pits.The 900W spot soft-hard coupling surface with the first-rate anti-wear performance.Above all,the conclusion is that the hardening phase with great plastic toughness and a certain proportion(50%)of inerratic surface distribution can markedly increase and promote the anti-wear performance of the material working surface,improve the contact surface of the fraction pair as well as stabilize the friction coefficient,this study can provide a reference for improving the surface wear of 40Cr parts.