Microstructural and mechanical characterization of high-alloy quenching and partitioning TRIP steel manufactured by electron beam melting

Abstract

The applicability of electron beam melting (EBM) as a powder-bed based process of additive manufacturing was examined for a high-alloy transformation-induced plasticity (TRIP) steel developed, in particular, for quenching and partitioning (Q&P) treatment. The chemical composition of the EBM manufactured material was determined to investigate the effect of EBM process on interstitial alloying elements such as carbon and nitrogen, which are relevant for the partitioning step. In Q&P state, tensile tests were performed and compared to the as-built as well as solution annealed state. In addition, these investigations were supplemented by microstructural characterization using electron backscatter diffraction. Compared to the as-built state, the tensile samples of Q&P state show a significant increase in yield strength of up to 1100 MPa with no significant decrease in ductility. Furthermore, it is shown that despite large defects resulting from the manufacturing process, material with extraordinarily high strength and good ductility was achieved. Finally, the EBM process on a high-alloy Q&P steel led to a fine-grained and texture-free martensitic microstructure, which develops due to solid-solid-phase transformations at elevated temperatures.