预热对27SiMn钢激光熔覆热影响区显微组织和力学性能的影响

采用激光熔覆技术在27SiMn钢表面制备了铁基熔覆层，考察了预热对27SiMn钢热影响区显微组织及力学性能的影响。结果表明，激光熔覆27SiMn钢热影响区出现大量马氏体组织；拉伸断裂断口由河流状解理面、撕裂棱及韧窝组成，表现为准解理断裂；预热处理有效减少了马氏体含量，且出现珠光体组织。预热温度100℃时，淬火层硬度下降25.4%、延伸率提升11.5%、抗拉强度下降14.3%。预热温度升高至300℃时，拉伸断裂方式转变为韧性断裂。适当的预热可有效减少27SiMn钢热影响区的马氏体组织，缓解淬冷导致27SiMn钢的韧性下降问题，提升激光熔覆27SiMn钢液压油缸的服役安全性。

Effects of Preheating on Microstructures and Mechanical Properties of Heat Affected Zone of 27SiMn Steel After Laser Cladding Process

A Fe-based cladding layer was prepared on the surface of 27SiMn steel by using laser cladding technique, and effect of preheating on the microstructure and mechanical properties of the heat affected zone (HAZ) of 27SiMn steel was investigated. The results show that a large amount of martensite appears in the HAZ of 27SiMn steel after laser cladding process. The tensile fracture is composed of river-pattern cleavage plane, tear edge and dimple, representing a quasi-cleavage fracture; preheating treatment effectively reduces the amount of martensite and brings pearlite structure. When the preheating temperature is 100 ℃, the quenched layer has its hardness decreased by 25.4%, elongation increased by 11.5%, and tensile strength decreased by 14.3%. When the preheating temperature rises to 300 ℃, ductile fracture occurs in the material under tensile force. Appropriate preheating can effectively reduce the martensite in the HAZ of 27SiMn steel and alleviate the decline in the toughness of 27SiMn steel caused by quenching, thus improving the safety during the service of hydraulic cylinder made of laser cladded 27SiMn steel.