The effect of heat treatment on the short term oxidation of 18/8 stainless steel in CO2

Samples of 18/8 stainless steel (type EN58A) have been vacuum annealed for 5h at 1073K in either a dynamic or a static vacuum. These, together with as recieved samples, were oxidised at 973K for 168h in one atmosphere of flowing CO2 and examined by scanning electron microscopy, energy dispersive x-ray analysis, x-ray diffraction and Auger electron spectroscopy. The elements manganese and carbon were removed from the bulk during annealing and the consequences of this on the stability of the austenite and hence on the subsequent oxidation characteristics are discussed. It is concluded that vaporisation of manganese and carbon during dynamic annealing could in certain cases result in the formation of ferrite in the steel. (author)