Microstructural analysis of high-pressure cold-sprayed Ni, NiCu and NiCu + Al2O3 coatings

• Highly dense coating structures of high-pressure cold-sprayed (HPCS) Ni, NiCu and NiCu + Al2O3 coatings
• Density was proven with Corrodkote tests.
• Impermeable structures were achieved with heat-treated HPCS NiCu + Al2O3 coatings.
• Heat-treated HPCS NiCu coatings had good cavitation–erosion wear behavior.

Cold spraying has shown its potential to produce metallic and composite coatings with high quality and performance. For instance, the impermeability of the coatings is the criterion for the corrosion resistance and thus, fully dense coatings can act as real corrosion barrier coatings. Our previous study has demonstrated the good corrosion properties of high-pressure cold-sprayed (HPCS) Ni and NiCu coatings whereas the present study focuses on the analysis of structural characteristics behind the dense coatings. Microstructures of as-sprayed and heat-treated HPCS Ni, Ni20Cu and Ni20Cu + Al2O3 coatings have been evaluated with FESEM from top-view direction. This revealed clearly particle deformation and particle boundaries whereas particle bonding was evaluated with cavitation–erosion test. Density was proven with Corrodkote test and impermeable HPCS NiCu + Al2O3 coating structures were achieved. Furthermore, cavitation–erosion resistance of NiCu coating was improved by heat treatment.