The oxidation resistance of fine-grained sputter-deposited 304 stainless steel

Abstract

The air oxidation of free standing 0.1 cm thick sputter-deposited and wrought 304 stainless steel specimens was studied and the long term oxidation weight gains of the sputterdeposited material were much less than weight gains for the wrought material at 800, 900, and 1000°C. The amount of scaling was also much less on the sputtered material and a thin, adherent oxide formed. The oxide on the sputtered material was more uniform in composition and was higher in chromium and manganese compared to oxide on wrought stainless and eventually formed MnCr₂O₄ after long periods of exposure. No stratified oxide layers, as typically observed in wrought stainless steel, formed on the fine-grained sputtered material. The improved scaling resistance of the sputter-deposited steel was attributed to a combination of grain boundary enhancement of chromium diffusion, reduced stresses in the oxide and mechanical keying of the oxide to closely spaced grain boundaries. The stability of grain size for the sputtered material (grain size ≤ 6 μm) also contributed to the better oxide adherence.