| Abstract Scope |
Spray forming suppresses macro-segregation and refines grains in superalloys due to its rapid solidification characteristics. However, microporosity and Laves phase segregation inevitably exist in the deposited microstructure. This study systematically investigated the effects of different hot isostatic pressing (HIP) temperatures (1080℃, 1130℃, 1180℃) on the densification behavior, phase transformation kinetics, grain growth mechanisms, and tensile properties of a spray-formed nickel-based superalloy. To isolate the direct impact of the HIP process, all specimens were characterized and tested in their respective as-processed states (i.e., as-deposited or as-HIPed) without any subsequent standard heat treatment. It was found that plastic flow and diffusion creep mechanisms during HIP significantly reduced porosity. As the HIP temperature increased, the Laves phase dissolved back into the matrix, and grain size followed growth laws governed by the failure of Zener pinning. Experimental results indicate that 1130℃ is the optimal HIP temperature. Under this condition, the alloy achieved a relative density of 99.87%, the volume fraction of the deleterious Laves phase decreased to 0.48%, and the best strength-ductility match was obtained (UTS: 1255 MPa, Elongation: 22%). This paper discusses the intrinsic connections between pore closure mechanisms, strengthening phase evolution, and fracture behavior, providing a theoretical basis and process guidance for the industrial preparation of spray-formed nickel-based superalloys. |