Stabilised mechanical properties in Ni-based Hastelloy C276 alloy by additive manufacturing under different heat inputs incorporated with active interlayer temperature control

Abstract

In this study, a Ni-based Hastelloy C276 alloy was prepared using cold metal transfer (CMT)-based directed energy deposition (DED) under different heat inputs with a zig-zag deposition path, integrated with active cooling and interlayer temperature control. Analogous mechanical properties were obtained for the fabricated alloys under different heat inputs (276, 368 and 553 J/mm) through effective interlayer temperature control. Such a broad processing window facilitates the large-scale industrial manufacturing and application of Hastelloy C276 by DED. Nevertheless, the lower heat input appears to slightly refine the microstructure and decrease the mechanical anisotropy of manufactured alloys, which is ascribed to combined effects of the manipulated bulk texture, refined dendrite arm spacing and reduced chemical segregation under lower heat input. Despite the variations of geometrically necessary dislocation (GND) densities with heat inputs, no significant change was observed in the average total dislocation density (TDD) in the microstructure of all samples as suggested by the peak profile analysis of Synchrotron X-ray diffraction data, which is advantageous for lowering the solidification cracking susceptibility. Moreover, all as-fabricated alloys present a typical strong fibre-type (200) crystallographic bulk texture measured by neutron diffraction, while such texture was relatively weaker in the lowest heat input condition. This work provides a reliable approach for stable additive manufacturing of Hastelloy C276 alloy, and innovatively presents rationales of stabilised properties based on the obtained insights into microstructure and bulk texture developments in a wide observation range by various techniques.