选区激光熔化及热处理工艺对钴铬合金力学性能的影响

Process and effects of heat treatment on mechanical properties of Co-Cr alloy manufactured by selective laser melting

系统研究了选区激光熔化(SLM)及热处理工艺对钴铬合金组织与性能的影响。通过设计正交实验,利用EOS M290选区激光熔化设备,优化钴铬合金成型的工艺参数;利用XRD、扫描电镜(SEM)、硬度仪及万能材料试验机对选区激光熔化钴铬合金的显微组织结构、物相组成及力学性能进行观察与测试。研究结果表明,选区激光熔化成型的最佳工艺参数为:扫描间距0.08 mm,扫描速度1110 mm/s,激光功率335 W,能量密度4.8 J/mm2,获得的致密度高达99.18%,且最佳的填充角度为67°。SLM成型的钴铬合金的物相主要由γ相及少量ε相共存,微观组织由细小均匀的胞状晶及柱状晶构成;其硬度、抗拉强度及延伸率分别为41.0HRC,1032 MPa,10%,断裂机制主要为穿晶脆性断裂。热处理后显微组织发生γ→ε相变,主要为ε相及少量γ相,并产生少量强化相M23C6(M=Cr,Mo,W);其硬度、抗拉强度及延伸率分别提升了6.1%,35.9%和17.6%,断裂机制主要为准解理断裂。

The selective laser melting （SLM） process of cobalt-chromium alloy and the effect of heat treatment on micro structure, mechanical properties were systematically studied. The orthogonal experiment was designed to optimize the process parameters by using EOS M290 SLM equipment. The microstructure, phase and mechanical properties were observed and tested by XRD, SEM, hardness tester and universal material testing machine. The results show that the optimum hatch distance is 0.08 mm, the scanning speed is 1110 mm/s, the laser power is 335W, the energy density is 4.8 J/mm^2 , the density is as high as 99.18%, and the optimum hatch angle is 67°. The phase of Co-Cr alloy formed by SLM is mainly composed of γ（fcc） and a small amount of ε（hcp） phases, and the microstructure of the alloy consists of fine uniform cell crystal and columnar crystal. The hardness, tensile strength and elongation of the Co-Cr alloy formed by SLM are 41.0 HRC, 1032 MPa, 10%, and the main fracture is transgranular ductile fracture. After heat treatment, the γ→ε phase transition will occur, the microstructure is mainly composed of ε phase and a small amount of γ phase, and produces a small amount of an enhanced phase M23C6 （M=Cr, Mo, W） ; the hardness, tensile strength and elongation are increased by 6. 1%, 35.9% and 17.6%, respectively; the main fracture is quasicleavage fracture.