The oxidation behavior of three different zones of welded Incoloy 800H alloy

Abstract

The oxidation behavior of three different zones of welded Incoloy 800H alloys, containing the substrate (800H-SUB), heat-affected zone (800H-HAZ) and the melt zone (800H-MZ) was studied at 950 °C in dry and wet air. The steady-state oxidation rate constants (kp values) were calculated based on the mass-gain data, and the oxidation resistant ability of the alloys followed by the rank of 800H-MZ > 800H-SUB > 800H-HAZ in dry air. The scales formed on the 800H-SUB and 800H-HAZ consisted of a heterophasic mixture of Cr2O3 and FeCr2O4, while a mixture of Cr2O3 and MnCr2O4 was observed on the 800H-MZ. On the other hand, the oxidation kinetics of the alloy, initially followed the parabolic-rate law up to 48 h, while a significant mass-lost kinetics was observed for a prolong exposure in wet air. The detail oxidation mechanisms for the alloys in both environments were investigated.