Microstructural evolution of a FeCo15Cr14Ni4Mo3 maraging steel with high ductility prepared by selective laser melting

Abstract

In this study, FeCo15Cr14Ni4Mo3, a new precipitation hardening martensitic stainless steel with ultra-high ductility, was used for selective laser melting (SLM). SLM technology is gradually applied in mold design and manufacturing, but there are still problems including materials. Maraging stainless steel with high ductility for additive manufacturing can greatly increase the life of mold and solve problems such as mold fracture. However, there are few maraging steels whose ductility after heat treatment exceeds 15%. From the examination of the microstructure characteristics, this study observed a large amount of martensite in the as-built samples and up to 50% of austenite (FCC) remained after aging. In addition, the heat-treated SLM FeCo15Cr14Ni4Mo3 sample shows a finer grain structure compared with the as-built samples. These microstructural features are favorable for enhancing the mechanical properties and ductility. Under optimized aging conditions, the SLM fabricated steel exhibits a tensile strength of 1484 ± 6 MPa, a yield strength of 1376 ± 4 MPa and a large elongation at break of 25 ± 0.6%. These results are promising for the application of the SLM fabricated FeCo15Cr14Ni4Mo3 parts in different fields such as molds.