Influence of Alloy 625 Manufacturing Process on 950˚C Oxidation Behavior in Air and Post-Oxidation High-Cycle Fatigue Performance

This study investigates the effect of the Alloy 625 manufacturing process on the high-cycle fatigue (HCF) performance of oxidized samples. Conventional manufacturing processes (wrought and casting) and additive manufacturing (AM) processes (laser powder bed fusion and direct energy deposition) were studied. Results of Alloy 625 isothermal oxidation at 950°C in air revealed that AM samples showed faster oxidation kinetics and enhanced intergranular oxidation (IGO) with associated voids; the latter two were attributed partially to the alloy's greater amount of interstitial oxygen compared to conventional manufacturing processes. The HCF results showed that oxidized AM samples have a shorter life than oxidized wrought counterparts, where the earlier crack initiation in the oxidized AM samples is attributed to greater oxidation-induced subsurface degradation. This subsurface degradation includes the enhanced IGO and associated voids.