利用激光熔覆技术在42CrMo钢表面制备了Stellite-6钴基涂层,然后在不同的温度下对涂层进行热处理,探究了热处理温度对涂层显微组织、硬度、耐蚀性和摩擦学性能的影响。结果表明:热处理能有效减小涂层内部的残余应力,消除裂纹、孔洞等缺陷;在900 ℃下进行热处理后,FCC结构的钴演变为HCP结构的钴,亚稳态M7C3型碳化物演变为稳态M23C6型碳化物;经过900 ℃×1 h的热处理后,涂层的近表面硬度是未热处理涂层的1.5倍,约为1300 HV;未热处理涂层的摩擦因数为0.42,磨损机理主要表现为塑性变形、犁沟及脆性剥落;热处理后,涂层的摩擦因数降至0.29,磨损机理主要为磨粒磨损和黏着磨损;热处理后生成的稳态M23C6型碳化物具有强化合金、提升涂层力学性能的作用;未热处理涂层与热处理涂层的自腐蚀电流密度均约为3.3×10 -3 A·cm -2,自腐蚀电位均在-0.29 V左右,单个容抗弧特征近乎重合。热处理过程中发生的再结晶和晶粒尺寸变化、马氏体相变对钴基涂层耐蚀性的影响不大。

Herein, a Stellite-6 cobalt-based coating was prepared on a 42CrMo steel surface using laser cladding technology; heat treatment was then conducted on the coating at different temperatures. Moreover, the effects of heat treatment on the microstructure, hardness, corrosion resistance, and tribological properties of the coating were investigated. Results show that the heat treatment can effectively reduce the residual stress in the coating and eliminate defects, such as cracks and holes. After heat treatment at 900 ℃, the faced centered cubic structure of cobalt evolves to hexagonal close-packed structure and metastable M7C3 carbide changes to stable M23C6 carbide. After 1 h of heat treatment at 900 ℃, the near surface hardness of the coating is 1.5 times that of the untreated coating, which is approximately 1300 HV. The friction coefficient of the untreated coating is 0.42, and its main wear mechanisms are plastic deformation, furrowing, and brittle spalling. However, after heat treatment, the friction coefficient of the coating reduces to 0.29, and its main wear mechanisms are abrasive and adhesive wear. The stable M23C6 carbide produced after heat treatment can strengthen the alloy and improve the mechanical properties of the coating. The self-corrosion current density of the coating after heat treatment is approximately 3.3×10 -3 A·cm -2, the self-corrosion potential is approximately -0.29 V, and the characteristics of the individual capacitive arcs nearly coincide. Further, the recrystallization and grain size variation during the heat treatment and martensitic transformation have no significant effect on the corrosion resistance of cobalt-based coatings.