Cold Spray of Ni-Based Superalloys: A Review on Processing and Residual Stress

Cold spray has been extensively applied to deposit a range of materials in many industries. In the recent times, such a method has also shown its potential to deposit nickel-based superalloys, which currently are in demand due to their high tensile strength and corrosion resistance (especially at elevated temperatures); however, cold sprayed nickel super alloy coatings have poor mechanical properties due to the materials’ limited ability to undergo plastic deformation. Regarding this, numerous cold spray process modifications have been experimented, including preheating substrate and feedstock powder, applying laser irradiation, heat treating coatings post deposition, and heat treating feedstock powder, to promote plastic deformation, eliminate porosity and enhance inter particle bonding. Specifically, the important influence of external heat input on the underlying substrate and/or the incoming particles during cold spray deposition was highlighted in multiple studies. These studies indicated that the addition of external heat during cold spray increased the adhesion strength of the coatings due to an increase in the thermal softening effect of the deposited particles. In general, an attempt is made here to systematically review the influence of cold spray process modifications on the microstructure, mechanical properties and residual stresses of nickel super alloy coatings.