MICROSTRUCTURAL AND MECHANICAL CHARACTERIZATION OF COLD SPRAYED INCONEL 718 DEPOSITS

Cold Spray is a solid state coating technology and has a high potential to serve as an additive manufacturing process. However, cold spraying of high strength materials is still challenging. For nickel-superalloys as Inconel 718, successful coating formation is challenging due to the limited thermal softening, which is necessary to reach adiabatic shear instabilities at internal interfaces. Thus, impact conditions have to be tuned for high particle temperatures in terms of a window of deposition. In the present study, two different Inconel 718 powders were cold sprayed under variation of the process gas temperature to investigate the role of softening on coating properties, such as bond strength, porosity, hardness, tensile strength, residual stress and electrical conductivity in as sprayed and annealed conditions. The results show that deposits with low porosity could be obtained and that strength and hardness improve with increased process gas temperature. Heat treatments of the coatings improve inter-particle bonding and enhance their mechanical properties. These results are the basis for successful manufacturing of Inconel 718 parts by cold spraying.