Metallographic Characterization and Comparative Analysis of SS-309L and Inconel 625 as Buffer Layer Materials on P91 Steel

SS-309L and Inconel 625 are recommended buffer layers between nickel-based hardfacing and P91 steel to avoid crack formation due to the martensite formation in heat affected zone (HAZ). These buffer layers have different metallurgical characteristics and significant cost difference. Hence, this article attempts to identify suitable buffer layer between SS-309L and Inconel 625. These buffer layers are deposited independently on P91 steel using flux cored arc welding followed by metallurgical characterizations. Metallographic results confirmed the presence of γ austenitic phases and columnar dendrites in both buffer layers. Lower HAZ hardness was observed due to absence of cube-shaped precipitates and high dilution of iron in SS-309L compared to Inconel 625. Coupled with cost effectiveness and metallographic observations, SS-309L material emerges as candidate buffer layer between nickel-based hardfacing and P91 steel.