High Temperature Oxidation of Type 430 Base Stainless Steels

High temperature oxidation has been made on four steels of type 430, i.e. Fe-16.6Cr (430-A), Fe-16.2Cr-0.4Ti (430-B), Fe-16.2Cr-0.3Zr (430-C) and Fe-17.6Cr-0.5Al (430-D) in wet oxygen containing up to 10 vol%H2O as well as in dry one between 1173 and 1473 K for 86.4 ks (24 h). 430-A has shown protections at 1173 K, 430-B at 1273 K, and 430-C and 430-D at 1373 K, irrespective of the environmental humidity. Above these temperatures, the mass gain curve of each steel shows breakaway, and the initiation and growth of the breakaway is accelerated by water vapour. The scale structures are duplicated and basically similar to each other, i.e. the outer layer being of type MnCr2O4 and the inner layer is of type (Fe, Cr)2O3. When steels contain Ti, Zr and Al, respectively, the internal oxidation of each element occurs. Zr and Al have shown strong contributions to adhesion of the scales. On the contrary, no contribution from the internal oxidation particles of Ti to the adhesion of the scales formed on 430-B has been observed.