Development and oxidation resistance evaluation of Al-rich surface layer on Alloy 617

Surface treatment was carried out for Alloy 617 to improve the high temperature oxidation resistance. After high purity Al was pre-deposited on the surface, electron beam (EB) was applied to form Al-rich micro-alloying zone with the depth of ~ 50 μm. In the micro-alloying zone, cellular and dendritic structures with very fine arm spacing were developed. In the oxidation test performed in air at 900 °C up to 1000 h, a transient oxidation behavior was observed for the surface-treated Alloy 617. During the short initial oxidation stage (< 1 h), Al-rich external oxide layers with the outermost spinel and inner alumina were quickly formed. However, during the steady-state oxidation stage, the oxidation rate of EB surface-treated Alloy 617 was substantially lower than that of the as-received Alloy 617.