Cold spraying of Inconel®625 thick deposits

Cold spraying of high strength materials, i.e., Inconel^®625 is still challenging due to the confined material deformability and thus high critical velocities, as well as occurring nozzle clogging affecting the quality of deposits. Thus, cold spray process parameters should be tuned and optimized to reach higher particle impact velocities as well as temperatures to allow Inconel®625 for high amounts of well-bonded particle-substrate and particle-particle interfaces, assuring high cohesive strength and minimum amounts of porosities. In this study, Inconel^®625 powder was cold sprayed on carbon steel substrates using N₂ as propellant gas under varied spray parameter sets, kinematics and powder sizes for a systematic evaluation. Coating microstructure, porosity, electrical conductivity, hardness, cohesive strength and residual stress were characterized in as-sprayed condition. Increasing the process gas temperature, pressure leads to low coating porosity of less than 1 % and higher electrical conductivity. The as-sprayed coatings show microstructures with highly deformed particles and well bonded internal boundaries. X-ray diffraction reveals that powder and deposits are present as γ-solid-solution phase without any precipitations. By work hardening and peening effects, the deposits show high microhardness and compressive residual stresses. With close to bulk material properties, the optimized deposits should fulfill criteria for industrial applications.