An investigation on the microstructure and compression properties of laser powder-bed fusion fabricated Hastelloy X Ni-based superalloy honeycomb structures

Abstract

One of the advantages of emerging additive manufacturing is providing opportunities to build parts with complex geometries. The microstructure and compressive response of Hastelloy X Ni-based superalloy honeycomb lattiaces fabricated by laser powder-bed fusion additive manufacturing is evaluated. The microstructural studies indicated that the as-built sample consisted of submicron cells with random orientations embedded in columnar austenite grains. The STEM-EDS observations revealed that the cell walls contained dense dislocation tangles rich in Mo and Cr elements compared to the cell interior. After the heat treatment at 1175 °C for 2 h, the partial recrystallization via twinning-assisted nucleation mechanism replaced some columnar grains with equiaxed ones. In addition, EBSD investigations illustrated that the recrystallized grains retained the texture of the parent grains, leading to the reduction of recrystallization kinetics through the creation of low-mobility boundaries. Upon the compression testing, the honeycomb samples showed stretch-dominated type behavior. The fractography results indicated that the initiation of cracks from the outer and inner surfaces of the honeycomb's walls was the failure mechanism of both as-built and heat trated honeycomb samples. Moreover, the compressive performance of the samples was slightly improved after heat treatment.