Progress of the Oxidation at 1000°C of a Low–Mn High–Cr Cantor’s Alloy in Natural Air

In order to discover how formed the multiple oxides observed in the final external scales after long exposure of a low–Mn high–Cr Cantor’s alloy to hot air, oxidation tests in furnace were performed for seven different durations. Metallographic characterization was carried out concerning the oxidation products obtained after each test duration. The different oxides did not appear one after the other, but simultaneously, at the early beginning of the exposure to hot air and after. They thickened all progressively and the chemical composition of each also evolved with time, more or less. Globally the innermost oxide is almost chromia much richer in Cr than in Mn while the outermost one contains Mn principally. The interrupted tests also allowed specifying the mass gain kinetic, which is parabolic, twice faster than a chromia–forming alloy. Despite the lowered content in Mn, manganese still plays an important role in the oxidation phenomenon, starting very early.