Work

Influence of increasing chromium content on additively manufactured tool steels: Microstructural and mechanical evolution before and after heat treatment

Year: 2024

Type: article

Abstract: Given the growing interest in additively manufactured martensitic tool steels, this study investigates the effect of increasing Cr content on the microstructure and mechanical properties of these steels. The analysis covers both the as-built (AB) condition and the condition after a typical heat treatment, which includes austenitization, quenching and multiple tempering steps. Thus, three Cr-alloyed tool steels, named Alloy A (20 wt.% Cr), Alloy B (22 wt.% Cr), and Alloy C (24 wt.% Cr), were analyzed in the AB and heat-treated (HT) conditions. Comprehensive microstructural characterization techniques, including light microscopy, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy unveiled a clear correlation between the Cr content and the resulting microstructural features and phase occurrences. An in situ synchrotron experiment identified the body-centered cubic-Fe phase in the alloys exclusively as δ-ferrite. Increasing the Cr content resulted in a higher amount of δ-ferrite in both AB and HT conditions, which consequently reduced the amount of martensite after heat treatment. Mechanical properties, evaluated through Vickers hardness and tensile testing, revealed a decrease in hardness and tensile strength with increasing Cr content and thus the δ-ferrite content. Additionally, changes in the deformation behavior from brittle to ductile were observed. This study thus contributes to a deeper understanding of the effects of increasing Cr content on the microstructural characteristics, phase occurrence and mechanical properties of high Cr-alloyed tool steels produced via additive manufacturing.

Source: Journal of Materials Research and Technology

DOI: 10.1016/j.jmrt.2024.12.169