Effect of pulse width on the mechanical properties and high-temperature steam oxidation resistance of Cr coatings deposited by high-power impulse magnetron sputtering

This study investigates the influence of pulse width parameters on the structural characteristics, mechanical properties, and high-temperature steam oxidation resistance of Cr coatings deposited on Zr-4 alloy using high-power impulse magnetron sputtering (HiPIMS). The findings reveal that all Cr coatings deposited by HiPIMS exhibit a (200) crystal plane preferential growth. Cr coatings deposited with narrow pulse widths possess dense structures with minimal columnar growth. As pulse width increases, the fiber texture of the coating becomes more pronounced, leading to a gradual decrease in hardness and scratch resistance. During steam oxidation at 1200 °C, Cr coatings deposited with wider pulse widths facilitate O diffusion due to enhanced columnar growth. This results in complete oxidation at an early stage, forming a dense oxide layer that impedes further inward O diffusion and outward Zr diffusion. In contrast, Cr coatings deposited with narrower pulse widths effectively slow down internal O diffusion owing to their denser structure. Consequently, a dense oxide layer forms on the surface, further restricting oxygen ingress. However, the remaining Cr layer fails to prevent the outward diffusion of Zr, resulting in the formation of ZrO₂ channels in a lattice pattern, which exacerbates the oxidation of the Zr substrate.