Microstructural and mechanical properties of high-performance Inconel 718 alloy by cold spraying

Abstract

As a precipitation-hardening nickel-based superalloy, Inconel 718 has decent corrosion resistance, high strength at ambient temperature, excellent creep and fatigue strengths at high temperature. In this work, high performance Inconel 718 alloy was fabricated by cold spray process. The microstructure evolution, hardness, adhesive strength and tensile strength were investigated systematically on the cold-sprayed Inconel 718 in as-sprayed and heat-treated conditions. The N2-processed Inconel 718 samples demonstrate a decreasing porosity with the increasing gas pressure, whereas the fully dense coating was obtained by using He gas. Consistent with the particle velocity measurement, higher adhesive and tensile strength were obtained at higher pressure of N2 propelling gas. Through the heat treatment at 990 °C for 4 h, the adhesive strength of N2 and He-processed Inconel 718 reached as high as 435.4 and 899.4 MPa, which is comparable with the tensile strength of bulk material. The microstructure and EBSD examination indicate the disappearance of particle boundaries after the diffusion during heat treatment. Besides, the He-processed Inconel 718 samples show a significantly improved ductility and ultimate strength comparable and even higher than those of bulk material. The results show that the high-performance Inconel 718 alloys can be fabricated by CS process for the application of damage repair and additive manufacturing.