Exploring the Effect of Si Content in Cr Coating on Its Microstructure and Properties

Four Cr-Si coatings with varying Si content ranging from 2 at.% to 9 at.% were deposited on the both surface of Zr-4 substrate. This study systematically investigated the effect of Si content on microstructure, mechanical properties, corrosion resistance and high-temperature oxidation resistance. Due to the lower Si content, only the Cr phase was detected in the Cr-Si coating, with Si existing in solid-solution. Therefore, all Cr-Si coatings exhibited good mechanical and hydrophobic properties. The addition of Si in the Cr coating significantly reduces the surface roughness compared with Cr coating. During the long-term autoclave test (30-day, 60-day and 90day) at 320 degrees C and 11.3 MPa, Cr-Si coatings demonstrated superior corrosion resistance attributed to the effective inhibition of further Si dissolution by the dense and continuous Cr2O3 layer forming on the surface. Additionally, after exposure to high-temperature oxidation at 1200 degrees C for 30 min, all Cr-Si coatings protect the substrate from oxidation. However, only the Cr0.91Si0.09 coating internally formed a dense and continuous in-situ Zr2Si diffusion barrier layer, which effectively reduce the Cr/Zr inter-diffusion, and sufficient Si prevent the outwards diffusion of Cr by forming Cr3Si boundary. The corrosion and oxidation mechanism have been studied in detail.