Evolution of structure and properties of the nickel-based alloy EP718 after the SLM growth and after different types of heat and mechanical treatment

The selective laser melting (SLM) process is used throughout the world. This process is based on the continuous (layer by layer) surfacing of metallic powder which is fused by laser or high-power electron beam. In this paper is presented studies of the structure of a nickel alloy (EP718) component formed using the SLM process, and the effects of heat treatment and hot isostatic pressing (HIP) on the mechanical properties of samples manufactured by SLM technology. Mechanical tests have shown that components formed using SLM exhibit a low level of strength but with a high degree of plasticity. Subsequent heat treatment led to an increase in strength and a corresponding reduction in plasticity owing to the formation of reinforcing particles of molybdenum silicides and an incomplete relaxation, with low grain growth. However, a combination of SLM + HIP + heat treatment resulted in optimum levels of strength and plasticity in comparison with other samples.