Using of Nickel Oxide NiO as a Diffusion Barrier in Aluminide Coating on Austinitic Stainless Steel AISI 321

Aluminum compounds are the most effective to resist the oxidation and corrosion at high temperature, because it has a good ductility and its capability to form a protective oxide scale Al2O3, such Alumina scale is known as thermally and electrically insulator and characterized with slow gowning rate. In this research we tried to prepare aluminide coating on austinitic stainless steel AISI 321, using a pack-cementation technique. The alloy surfaces were doped with a thin nickel oxide layer before aluminising using an adhesive materials. The coating produced was subjected to a cyclic oxidation and hot corrosion tests. The coating structure and coating behaviour after the treatment were studied using X-rays and optical microscope. The coatings produced were posses a high resistance to oxidation under atmospheric pressure at 900C, but not in presence of a molten salt Na2SO4 at 884C.