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 µm and 0.2 µm, 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 α-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.
In this work, the corrosion resistance of AISI 321 stainless steel is increased through. the two-stage implantation of oxygen ions and of both aluminum and boron ions together. During ion implantation, a modified layer with a thickness of about 200 nm is formed, which affects the properties of material. The increase in corrosion resistance is confirmed by prolonged acid corrosion tests at pH 3.5 and by accelerated electrochemical tests using a potentiostat. The corrosion rate of the implanted sample is 0.708 μA/cm2, in contrast to the non-implanted sample (1.26 μA/cm2). The modified surface layer is examined using X-ray photoelectron spectroscopy (XPS), secondary-ion mass spectrometry (SIMS), and transmission electron microscopy (TEM). Aluminum and boron are implanted to a depth of more than 250 nm. It is found that the modified surface of the stainless steel substrate contains oxides of implanted ions (Al2O3) and oxides of substrate ions (Cr2O3 and NiCr2O4).
In this work, multilayer ceramic-metal coatings (Metal/nitride ceramics/ Metal/oxide ceramics) with increased corrosion resistance were obtained. The structure of each layer of the obtained coatings was researched using the transmission electron microscope JEOL JEM-2100. The metal layers had a columnar crystal structure, the layers of nitride ceramics predominantly had a nanocrystalline structure (grain size was about 15 nm), the layers of oxide ceramics were amorphous. Corrosion resistance was evaluated on a potentiostat P-45X in a 0.5 M NaCl solution using a three-electrode cell. The created coating reduced the corrosion rate of the stainless steel substrate by an order of magnitude.
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