Microstructural and Mechanical Characterization of Spray-Formed and Vacuum Cast AISI 440C-Mod Martensitic Stainless Steel

Abstract The spray-forming process is a promising processing route for producing high-performance high-carbon steels. In this study, as-received and hardened/tempered spray-formed (SF) AISI 440C-Mod steel is compared to its vacuum cast (VaC) counterpart. For materials microstructure characterization scanning electron microscopy, X-ray diffraction analysis, energy dispersive spectroscopy, and electron backscatter diffraction were utilized. For the characterization of the mechanical properties and performance hardness, tensile, and compression testing were performed. The results show that the SF steel has a microstructure that is very different from the VaC condition. The differences in the microstructure of the steels after the different processing routes can be explained consistently by differences in the solidification rate and the rate of subsequent cooling of the solidified structure. In particular, the identity, morphology, and size of the primary carbides depend strongly on the combination of solidification and cooling rates. The differences in microstructures have a decisive influence on the mechanical properties of as-manufactured and hardened/tempered steels. The present findings demonstrate the potential of spray forming to produce high-performance AISI 440C-Mod martensitic stainless steel with improved mechanical properties compared to VaC steel.