Oxidation of Austenitic Stainless Steel Boiler Tubing in Carbon Dioxide

Abstract

The long-term oxidation characteristics of austenitic stainless steel boiler tubing in CO₂₋ vol.-% CO at up to 600 psig and at 650° and 700° have been studied. Weight gams, metallography and microprobe analysis indicated that heavily cold-worked material showed the best oxidation resistance owing to the formatiOn of a Cr₂O₃. protective scale. Oxidation of material heat-treated in nitrogen at the lower temperatures. resulted in the formation of a rather less resistant ‘spinel’ type oxide, while the material heat-treated in nitrogen at the higher temperature suffered severe pitting attack. Heat treatment in air at all temperatures provided a fairly resistant oxide film during subsequent oxidation in CO₂. Hence heat treatment in air is preferable to heat treatment in nitrogen, and leaving the heat-treatment scale on surfaces which are subsequently to be exposed to CO₂-based environment is recommended. Type 316 stamless steel showed rather better oxidation resistance than Type 347 stainless steel.