The Oxidation Behaviour of Fe–14Cr Alloys with Small Additions of Al at High Temperatures

Abstract

A study has been made on the effects of low Al addition, 0.1–2.0%, on the oxidation behaviour of Fe–14Cr alloys in flowing atmospheric oxygen in the temperature range 900–1200°C. Oxidation has not appeared to follow any simple rate law, indicating some complexity in the scaling process. A minimum has been found to appear at 0.3%Al in the weight gain vs Al content relation after oxidation for 24 h with the exception that 2.0%Al alloy show better oxidation resistance below 1000°C. The extent of spalling and nodular growth of scale increases with increasing Al content in the range from 0.3–2.0%Al. Cross-sectional examinations have revealed the formation of the internal oxidation zone of α-Al2O3 particles for all but 2.0%Al alloy. It has been deduced that the internal oxidation zone plays an important role in the formation and stabilization of the outer protective (Fe, Cr)2O3 layer rich in Cr as well as a role such as giving sites for vacancy sink. The good oxidation resistance observed in 0.3%Al alloy is thus considered to be mainly due to the internal oxidation in the best form among the alloys tested.