Auxetic Behavior and Compressive Performance of Additively Manufactured Inconel 718 Tetra-Chiral Structures for Aerospace Turbine Applications

Abstract

The tetra-chiral auxetic structure was fabricated from Inconel 718 superalloy using selective laser melting (SLM) at various relative densities (25, 50, and 75%) and cell sizes (2 and 3 mm). A quasi-static compression test was conducted both experimentally and numerically to assess the effect of the negative Poisson’s ratio on the compressive stress–strain relationship of the auxetic structure. Morphological examination of IN718 superalloys revealed cellular and columnar dendritic structures. The experimental results show that the tetra-chiral auxetic structure with a 2 mm cell size and 75% relative density exhibits an ultimate compressive strength of 1004.17 MPa and a yield compressive strength of 237.20 MPa, which are higher than those of the 3 mm cell size structure. The experimental results were validated against 2.5D models through FEA analysis, which shows a stronger correlation between the FEA simulations and the experimental results. The enhanced negative Poisson’s ratio of − 1.96 was achieved at a 3 mm cell size, compared with 2 mm, due to the variation in cell size and relative density. The deformed tetra-chiral auxetic structure showed crack propagation, and elongated grain patterns formed under the compressive load. The tetra-chiral auxetic structure with a 2 mm cell size and 75% RD exhibits excellent weight reduction and mechanical properties under compressive loads, making it suitable for potential applications in aero-turbine blades.