Corrosion Behavior of a Cr-Al Coating Deposited on 304 Austenitic Stainless Steel by Multi-Arc Ion Plating in Liquid Lead–Bismuth Eutectic

In this paper, a Cr-Al coating was deposited using multi-arc ion plating (MAIP) on 304 austenitic stainless steel. The Cr-Al-coated sample was treated by vacuum annealing at 600 °C for 12 h, and its corrosion behaviors against static LBE were carefully evaluated by SEM, EDS and XPS at a temperature of 600 °C for 1000 h, compared with an uncoated sample. The results showed that the uncoated sample was corroded by the dissolution and oxidation of LBE severely; a duplex-layered oxide layer consisting of an outer Fe3O4 magnetite layer and an inner FeCr2O4 spinel layer was produced on the surface of 304 stainless steel after LBE corrosion. For Cr-Al diffusion coating, an oxide layer was formed that separated the LBE into the 304 matrix. XPS detection showed that the oxide layer primarily included Al2O3. Besides this, the hardness of the coating was tested with a Vickers hardness tester, and the annealed Cr-Al diffusion coating exhibited an average hardness of 260 HV, about five times as high as the Al coating before annealing, of which the average hardness was 48 HV.