Characterization of Engineered Nickel-Base Alloy Surface Layers Produced by Additive Friction Stir Processing

Abstract

Additive friction stir processing (AFSP) was used as a novel method to create consolidated γ′-strengthened superalloy surface layers on non-age-hardenable Ni-alloy substrates. A Ni-Cr-Mo superalloy (Haynes Alloy 282) was deposited onto Ni-Cr-Fe alloy (INCONEL™ Alloy 600) plate using a cold-wire gas tungsten arc process and subsequently friction stir processed. Alloy 282 was incorporated into the surface and led to increases in near-surface hardness to levels over 275 HV0. 3 as-processed. Heat treatment response and precipitate distribution also improved as a result of AFSP. The application of AFSP led to a 2-fold increase in hardness after a direct age heat treatment relative to the as-deposited GTAW weld overlay without AFSP. Enhancement of precipitate formation kinetics was attributed to stored energy from mechanical stirring of the additive Alloy 282 at high temperature. Electron backscatter diffraction and transmission electron microscopy of AFSP regions showed increased dislocation density for low AFSP heat input processing parameters. © 2013 Springer Science+Business Media New York and ASM International.