The effect of temperature during plasma nitriding on the properties of IN718 additively manufactured by laser beam powder bed fusion.

The IN718 superalloy has become a strategic alloy for applications in critical components in aerospace, oil, and gas, or power generation. Commercially, IN718 is produced by conventional casting processes. However, manufacturing is evolving towards 3D printing, which allows the manufacturing of near-net-shape parts and complex designs, thus optimizing manufacturing steps, reducing production costs, and adding other advantages to the final product. However, high corrosion resistance and mechanical strength are required in applications such as oil and gas, whereas IN718 superalloys have limitations. Surface hardening by applying plasma nitriding can protect against corrosion by increasing mechanical strength and wear resistance. For this, plasma nitriding has been widely applied for surface hardening of IN718; however, little is found on the effects of surface treatments (coating or nitriding) of additively manufactured alloys. The effects of temperature during plasma nitriding on the surface properties of IN718 superalloy 3D printed by the Laser Beam Powder Bed Fusion (LB-PBF) method are reported here. Samples of IN718 fabricated by 3D printing were plasma nitrided at fixed temperatures between 500 and 650 °C in a semi-industrial reactor, their effects are analyzed and correlated with their microstructural characteristics, the mechanical properties at the micro- and nanoscale, and the tribological responses in a pin-on-disk configuration. [Display omitted] • PN at 500 °C produced the γ N coexisting with c-CrN and the fine crystalline γ-(Ni,Cr,Fe) phases. • PN between 550& 650 °C produced the γ Cr-depleted and the c-CrN hardening phases. • HV increases with PN at 500 °C to 575 °C, and neglectable changes in nano-hardness & E are detected. • The elastoplastic behavior of the IN718 PN at 500 °C was better than the nitriding at 650 °C. • Wear resistance of the 3D-printed IN718 is strongly improved upon plasma nitriding at 500 °C. [ABSTRACT FROM AUTHOR]