热处理对激光选区熔化成型高速钢组织和力学性能的影响EI北大核心CSCD

基于激光选区熔化(selective laser melting,SLM)技术,采用加热打印基板和低功率慢扫描的打印策略,制备了近全致密、低缺陷的高速钢样品;对比分析了固溶淬火及1~4次高温回火等热处理工艺对高速钢显微组织及力学性能的影响。结果表明:SLM极高的熔融/冷却速率产生了细晶奥氏体组织,解决了高速钢中常见的粗大莱氏体组织和网状碳化物问题。固溶淬火处理后高速钢组织由马氏体和残余奥氏体组成。随后在数次高温回火过程中,高速钢逐渐向回火马氏体转变,并析出大量微米级和纳米级MC型碳化物。在马氏体相变强化和MC型碳化物沉淀强化作用下,固溶淬火+3次回火的Tempered-Ⅲ样品硬度60HRC,抗弯强度3621 MPa,弯曲断裂应变为10.1%,获得硬度、强度和韧性匹配较佳的综合性能。继续增加回火次数则导致部分碳化物长大,使得高速钢弯曲断裂应变有所降低。通过SLM技术结合固溶淬火+高温回火,能够充分发挥细晶强化、相变强化和沉淀强化效果,为高强高韧复杂形状高速钢零件的快速制备提供了新途径。

Effect of heat treatment on microstructure and mechanical property of selective laser melted high speed steel

Based on selective laser melting (SLM), the high speed steel samples with nearly full density and low defects were prepared by using the printing strategy consisted of preheated printing substrate, low laser power and slow scanning speed. The effect of solid-solution oil-quenching as well as 1-4 times high temperature tempering on the microstructure and mechanical properties of selective laser melted high speed steel was contrasted and analyzed. The results demonstrate that fine austenite grains can be obtained due to the high melting/cooling rate in SLM process, solving the problems of coarse ledeburite organization and carbide network in high speed steel. The structure of steel is martensite and retained austenite after solid-solution oil-quenching. High speed steel sample transformed into tempered martensite during multiple tempering, accompanied with a large number of micro-sized and nano-sized carbides precipitated. The quenched and triple tempered Tempered-Ⅲ sample has a hardness of 60HRC, a flexural strength of 3621 MPa and a bending fracture strain of 10.1%, exhibiting an outstanding combination of hardness, strength and toughness. The bending fracture strain of high speed steel decreases owing to the coarsening of carbides in four times tempering. The integration of SLM, solid-solution oil-quenching and high-temperature tempering, which forms the combined effects of fine-grain strengthening, martensitic hardening and precipitation strengthening, provides a new approach for complex shaped high speed steel parts with high strength and toughness.