Influence of Different Copper Feedstock Powders on the Microstructure and Corrosion Resistance of Coatings Prepared by Cold Gas Spray

The purpose of this study is to investigate the effect of copper powder oxidation on the deposition efficiency, microstructure, wear and corrosion resistance. The gas-atomized copper powders in the as-received (Cu-Safina and Cu-FST) and oxidized states (Cu-treat, oxidized in air, 25 °C for 5 months; Cu-treat1, oxidized at 100 °C for 1 h; and Cu-treat2, oxidized at 200 °C for 1 h) were used to prepare the coatings by cold gas spray (CGS). XPS analysis detected Cu₂O and CuO for all feedstock powders, increasing for oxidized ones. The deposition efficiency and thickness of the coatings followed the order: Cu-Safina > Cu-FST > Cu-treat1 > Cu-treat > Cu-treat2. For oxidized coatings, SEM images showed more defected microstructure, increase in pores, and microcracks. Cu-FST coating showed a sliding wear rate of (0.13 ± 0.01) × 10^-4 mm³ N⁻¹ m⁻¹), and abrasive wear rate of (3.2 ± 0.2) × 10⁻⁴ mm³ N⁻¹ m⁻¹. Gas-atomized powder coatings showed a better corrosion resistance performance. The electrolyte did not reach the substrate/coating interface for t ≥ 700 h and the coatings resisted for 2000 h in salt fog tests. However, oxidized coatings showed low corrosion resistance due to the presence of cracks and defects, and the coating/substrate was severely damaged after ≈100 h in 3.5wt.%NaCl solution.