Growth behavior of oxide forming on a sputtered oxygen-enriched type 304 stainless steel

Type 304 stainless steel was deposited with and without added oxygen and then oxidized at 900 °C in 0.1 atm oxygen. The oxidation rate of the oxygen-enriched steel was lower than that of the steel without added oxygen, and the oxide adhesion was better. Line scans on cross-sectioned scale on the oxygen-enriched steel showed that inward oxygen diffusion had occurred; however, this was not shown by any of the line scans on the steel without added oxygen. The diffusion rate of cations through chromia scale was reduced by the oxygen enrichment. A secondary ion mass microscopy study showed that sulfur segregation to the oxide scale occurred during oxidation. The extent of this segregation for the oxygen-enriched steel was much lower than that for the steel without added oxygen. The results are explained in terms of the sulfur effect theory by postulating that impurity sulfur segregated to oxide particles in the oxygen-enriched steel, resulting in a reduced sulfur level in the scale and at the oxide/metal interface.