Feedstock modification and microstructural characterisation of Cold Spraying of Inconel 718

Cold spray is a solid-state deposition technique which employs the kinetic energy of the feedstock, conserving the original microstructural characteristics of the particles upon the deposition process. Inconel 718 has been practically applied due to its remarkable high tensile strength and corrosion resistance at an elevated temperature, which derives from its complex alloying chemistry. This superalloy can be deposited via cold spray process for multiple applications; however, cold spraying Inconel 718 demonstrates porosity and delamination, which have been attributed to limited plastic deformation, sourcing from the existence of hard precipitates. This research aims to enhance the deformability of the alloy by modifying the feedstock microstructures prior to deposition through solution treatment process at 950 °C and 1050 °C. It was observed that the γ'' phase has transformed into a stable δ precipitate at 950 °C. Higher treatment temperature at 1050 °C shows a complete solution transition, proven by XRD, EBSD phase map, and electron channelling contrast imaging (ECCI). The cold sprayed solution treated Inconel 718 at 950 °C particles indicate a metallurgical improvement at the coating interface, followed by porosity reduction of nearly 60% when compared to the as-sprayed Inconel 718 feedstock.