Effect of cold work on the oxidation resistance of2tfrac{1}{4} Cr-1 Mo steel

The effect of cold work on the oxidation rate of 21/4 Cr-1 Mo steel in pure oxygen at 1 atm pressure at temperatures ranging from 400 to 950C has been studied for short exposure periods (max. 4 hr). The specimens had been cold worked up to 90% by cold rolling. The results indicate negligible effect of cold work on the oxidation kinetics up to 700C, beyond which there is general reduction in oxidation. The effect was pronounced at 900C. The increased resistance to oxidation has been attributed to the faster diffusion of chromium in the cold-worked material compared to the annealed one, leading to the formation of a chromium-rich spinel which helps in slowing down the oxidation of the alloy. The findings have been corroborated by the examination of all samples oxidized at 900C by optical, EPMA, SEM, and EDAX analyses.