Abstract
Formation of a surface layer containing a high concentration of aluminum on SUS304 stainless steel was tried by electrodeposition of Al on the steel using potentiostatic cathodic polarization method in NaCl-KCl melt containing AlF3. In addition, improvement in spallation resistance of the steel was accomplished by electrodeposition of La in the same molten salt containing LaF3. The cyclic oxidation resistance of the electrodeposited sample was investigated at 1273K in air containing water vapor. The deposited layer formed after Al electrodeposition uniformly coated the substrate steel, and was adhesive to the substrate steel. The deposited layer consisted mainly of Fe aluminides. The particles of La were observed on the surface of the deposited layer when the electrodeposition of La was carried out after the Al electrodeposition. The cyclic oxidation test in atmosphere containing water vapor showed that for the untreated steel, a large mass loss was observed, while for the steel with Al deposition, this behavior was largely improved. For the SUS304 steel with Al and La depositions, the mass loss became small as compared with the steel with only Al deposit, showing that the cyclic oxidation resistance of the steel with Al and La depositions was extremely high. For this case, it was found that a protective scale consisting of α-Al2O3 was formed on the deposited layer surface.
