选区激光熔化Mar-M509合金成形性能及热处理工艺研究

Study on Formability and Heat Treatment of Mar-M509 Superalloy by Selective Laser Melting

摘要:

针对选区激光熔化（SLM）成形Mar-M509合金进行了打印工艺参数优化，得到孔隙和微裂纹较少的优化工艺参数。并设计固溶、固溶+时效两种热处理制度，研究热处理对显微组织及力学性能的影响。与直接打印态样品相比，热处理主要导致两种析出相的产生，亮白色近圆形富Cr-Co碳化物颗粒和暗灰色不规则长条形富Ta-W碳化物。室温拉伸试验结果表明，沉积态样品表现出高的抗拉强度和屈服强度，固溶热处理后的抗拉强度降低500MPa，固溶+时效热处理后抗拉强度下降约350MPa。造成强度降低的主要原因是热处理过程中发生了晶粒粗化和残余应力消除。固溶处理后样品中析出物以富Cr- Co碳化物为主，少量大尺寸Ta-W碳化物沿晶界析出。固溶+时效处理后Ta-W碳化物含量增加，以沿晶界和晶内两种方式存在。热处理后材料塑性未得到改善，两种热处理制度均导致产生大量沿晶界析出的碳化物，推测会对材料塑性产生不利影响。为了改善SLM Mar-M509的强度和塑性，需通过热处理工艺对析出碳化物的尺寸和分布进一步调控。

Abstract:

The printing process parameters of Mar-M509 alloy formed by selective laser melting (SLM) are optimized. The optimized process parameters with less pores and microcracks are obtained. Two heat treatment systems of solution and solution + aging were designed to study the effects of heat treatment on microstructure and mechanical properties. Compared with as-built samples, heat treatment mainly leads to the production of two precipitates: bright white nearly circular Cr-Co rich carbide particles and dark gray long strip Ta-W rich carbide. The tensile test results at room temperature show that the as-built samples have a high tensile strength and yield strength. After solution treatment, the tensile strength of the sample decreases by 500MPa, while the tensile strength of the sample after solution + aging treatment decreases by about 350MPa. The main causes of strength reduction are grain coarsening and residual stress elimination during heat treatment. After solution treatment, the main precipitates are Cr-Co rich carbides with a small amount of large-size Ta-W carbides precipitate along the grain boundary. After solution + aging treatment, the content of Ta-W carbide increases and exists along grain boundary and in grain. The plasticity of the Mar-M509 superalloy has not been improved after heat treatment. Both heat treatments lead to a large number of carbides precipitated along the grain boundary, which is speculated to have an adverse effect on the plasticity. In order to improve the strength and plasticity of SLM Mar-M509 superalloy, the size and distribution of precipitated carbides need to be further regulated by heat treatment.