Plane-strain fracture toughness of thin additively manufactured maraging steel samples

Abstract

This study aimed to evaluate the aging effects on mechanical properties of 18Ni (300) maraging steel processed by additive manufacturing powder bed fusion and subjected to different aging conditions. The aging temperatures were 470 °C, 510 °C, and 530 °C, with exposure times ranging from 0.33 to 96 h, followed by air cooling. Despite the layer-by-layer material consolidation mechanism, weak preferred orientation was found in the as-built condition; moreover, only martensite and austenite were found in the X-ray diffraction results. This alloy showed a steep increase in hardness, compressive strength, and tensile strength, while the work-hardening ability decreased with aging. Despite using thin single-edge bending samples (5 mm), the plane-strain fracture toughness (KIC) size requirement was met, and valid KIC results were 49 ~ 64 MPam. This result could help design new additive manufacturing applications of high-strength steel, such as thin-walled, lattice structures, and reduced cross-section parts projected to minimize weight in different industries.