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

The printing process parameters of Mar-M509 alloy formed by selective laser melting (SLM) were optimized. The optimized process parameters with less pores and microcracks were obtained. Effects of heat treatment on microstructure and mechanical properties were studied by two heat treatment systems of solution and solution+aging. 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 500 MPa, while the tensile strength of the sample after solution+aging treatment decreases by about 350 MPa. 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, which exists along grain boundary and in grain. The plasticity of the Mar-M509 superalloy does not improve 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. © 2022 Rare Metals Materials and Engineering Press. All rights reserved.