Si-Al-N-O Multi-Layer Coatings with Increased Corrosion Resistance Deposited on Stainless Steel by Magnetron Sputtering

This work studies single-layer (Al-Si-N) and multi-layer (Al-Si-N-O/Al-Si-O) coatings deposited by magnetron sputtering on stainless steel specimens (AISI 321), which can be used under aggressive conditions. The multi-layer coating consists of six alternating layers of Al-Si-N-O and Al-Si-O with a thickness of 0.9 mu m and 0.2 mu m, respectively. The structural-phase state and the chemical composition of the coatings were studied by transmission and scanning electron microscopy and XPS analysis. It was revealed that single-layer coatings are nanocrystalline and contain AlN and alpha-Si3N4 phases. Multi-layer coatings (Al-Si-N-O/Al-Si-O) are amorphous in each of the layers. The corrosion properties of substrate and coated specimens were investigated using a potentiostat in the 3.5 mg/l sea salt solution. It was found that corrosion resistance of stainless steel specimens with multi-layer coating is substantially (tenfold) higher compared with substrates and the specimens with single-layer coating.