Influence of Cr3C2 Additions to AISI H13 Tool Steel in the LPBF Process

Tool steels are known to be difficult to process by laser powder bed fusion as they were not designed to fit the welding or additive manufacturing (AM) process route. Hot cracks and cold cracks are known to occur in such alloys. To gain insights on limits of alloying contents regarding primary carbides in the melt, powder blends based on AISI H13 with additions of Cr3C2 carbides are processed by laser powder bed alloying (LPBA) herein. The LPBA process is evaluated based on demixing phenomena observed in the macroscopic chemical composition of the specimen. In-depth microstructural analyses are carried out to understand the metallurgical behavior of the new alloy and are accompanied by Calphad modelling. Hardness tests characterize the alloy's suitability as a novel tool steel. The alloy's hot cracking tendency is reduced by systematic additions of Cr3C2 to AISI H13 which narrow the solidification interval. Hardness tests after martensitic hardening without annealing have shown the applicability of the new alloy as AM tool steel. Apparent chemical gradients over the build plate demonstrate that further research is needed to improve the technology of LPBA for processing these novel alloys.