Surface Microstructure Evolution and Mechanical Property Investigation of Inconel 718 Alloy Using Multiple Trimmings and WEDM

The nickel-based Inconel 718 alloy, known for its high strength, hardness, and temperature resistance, is widely used in cutting-edge industries such as aerospace. However, after wire electrical discharge machining (WEDM), the alloy surface can experience varying degrees of thermal damage, leading to a significant deterioration in the service performance of manufactured parts. In this study, single-factor experiments were conducted on the nickel-based Inconel 718 alloy to investigate the effects of different machining parameters on the surface quality, material removal rate, and microstructure. Using Taguchi experiments, parameter combinations that achieved the maximum material removal rate and minimum surface roughness were obtained. Based on parameter optimization, multiple trimming strategies were employed to study the effects of multiple trimming on the evolution of the surface microstructure and mechanical properties of Inconel 718 alloy parts. The results showed that with an increase in the number of trimmings, the thermal damage to the surface gradually decreased. After multiple trimmings, the roughness average (Ra) value was reduced to 0.396 μm, the recast layer thickness was reduced from 9.035 μm to 0.92 μm, and the surface hardness approached that of the substrate, effectively removing the surface-hardened layer. The tensile strength of the samples after multiple trimmings increased by 52.2 MPa. The fracture strain of the main cutting was 63.1%, while that after multiple trimmings was approximately 67%. The stress required to fracture the sample increased, thereby enhancing the mechanical properties. The thickness of the brittle fracture zone at the fracture edge was reduced from 18.89 μm to 6.65 μm. The findings indicate that parameter optimization and multiple trimming strategies can improve the surface quality and mechanical properties of Inconel 718 alloy workpieces.