Mitigating the Anisotropy of the Microstructure and Mechanical Properties of L-PBF-Fabricated H13 Steel via Rare Earth Ce Addition

TL;DR

Adding rare earth cerium (Ce) to H13 steel during 3D printing reduces directional differences in its structure and strength, making it more uniform.

Contribution

Ce addition is shown to mitigate microstructural and mechanical anisotropy in L-PBF H13 steel for the first time.

Findings

Ce transforms columnar grains into equiaxed grains, reducing anisotropy.

Ce-containing samples show minimal elongation difference (0.2%) between building and scanning directions.

Ce increases retained austenite content and improves tensile strength and ductility.

Abstract

H13 tool steel is widely used in the hot work die industry owing to its excellent mechanical properties. However, the inherent anisotropy of its microstructural and mechanical properties during additive manufacturing (AM) via laser powder bed fusion (L-PBF) hinders its broader application. In the current study, Ce-containing and as-built samples were prepared in both vertical and horizontal directions, and their microstructures and tensile properties were investigated. Notably, the grain size of the vertical samples is approximately 2.7 μm, which is 19.2% smaller than that of the horizontal samples in L-PBF H13 steel. In addition, the retained austenite (RA) content in the vertical samples reaches as high as 19.7%, whereas in the horizontal samples, it is only 0.4%. After the addition of Ce, the columnar grains of the building direction (BD) samples transform into equiaxed grains. The RA content of the scanning direction (SD) samples and BD samples is 6.3% and 5.7%, respectively. The tensile test results further demonstrate that Ce-containing BD samples exhibit a tensile strength of 2025.3 MPa and an elongation of 17.3%, with the elongation difference between the two directions being only 0.2%. The addition of Ce reduces microstructural anisotropy, resulting in a significant decrease in the mechanical property anisotropy of the formed parts.

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