Effect of the possible fcc stabilizers Mn, Fe, and Ni on the high-temperature oxidation of Co-Cr alloys

Abstract

Earlier studies have suggested that manganese might be attractive as an alternative fcc stabilizer to nickel in cobalt base alloys because of its beneficial effect on the sulfidation resistance. Because it has relatively high oxygen affinity, it seemed possible that it might modify the ability of the alloys to form a protective Cr ₂O₃ scale. Thus, a range of alloys having compositions close to the critical Co-20 Cr value have been investigated in the temperature range 900–1150° C for times up to 240 hr in air and oxygen. Similar, but less extensive studies, have been conducted on alloys containing iron or nickel. None of these elements has a significant effect on the oxidation behavior, or on the ability of the alloys to develop a protective Cr ₂O₃ layer. However, manganese has a significant adverse effect on the scale spallation, apparently because of its increasing the brittleness of the oxide, particularly the CoO.