Corrosion resistance and oxidation resistance of CoCrFeNiCu high entropy alloy coatings prepared with different sputtering powers

Abstract

In order to explore the influence of magnetron sputtering process parameters on the corrosion resistance and high-temperature oxidation resistance of CoCrFeNiCu coatings, the coatings were prepared by DC magnetron sputtering with different sputtering powers (50, 100, 150, and 200 W). The phase compositions, microstructures, and corrosion resistance of the coatings were tested using X-ray diffraction, scanning electron microscopy, energy spectrum analysis, and electrochemical experiments. The high-temperature oxidation resistance of the coatings was measured using the cyclic oxidation method. The influence of sputtering power on the high-temperature oxidation resistance of the coating was explored by analyzing its oxidation kinetics curve and the surface morphology of the oxide layer. The results showed that the coating prepared with the sputtering power of 50 W had a quasi-amorphous structure and better corrosion resistance. However, with the increase in sputtering power, the coating grains became coarser gradually, and its corrosion resistance decreased. The oxidative kinetic curves of the coatings prepared at the lower power increased roughly linearly with oxidation time at 800 ℃ in the air, and an amount of pores appeared on the surface of the oxide layer, which weakened the oxidation resistance of the coating. The oxidation kinetic curves of coatings prepared at the higher power presented a parabolic change, and the formed oxide layers became relatively dense, which could effectively protect the coatings. Therefore, the larger thickness and the higher hardness of the CoCrFeNiCu coating with an FCC solid solution prepared at the higher sputtering power are beneficial for improving the oxidation resistance of the coatings at elevated temperature.

Keywords

• cocrfenicu high entropy alloy coating
• sputtering power
• microstructure
• microhardness
• corrosion resistance