Influence of Heat Treatment Process on the Microstructure and Properties of 304 Stainless Steel Formed by Electron Beam Fuse Deposition

This study investigates the effects of post‐deposition heat treatment on the microstructure and mechanical properties of electron beam fuse deposited 304 stainless steel. Specimens undergo three heat treatments: 1) annealing at 850 °C (air cooling), 2) solution treatment at 1050 °C with air cooling (ST+AC), and 3) solution treatment at 1050 °C with water quenching (ST+WQ). All heat treatments significantly reduce magnetic response due to martensite reversion, yielding a predominantly single‐phase austenitic microstructure. Furthermore, thermal expansion of deposition‐induced gas pores reduce density in all heat‐treated specimens. Solution treatment with air cooling forms lath martensite with diminished austenite grain boundaries. Conversely, water‐quenched solution treatment enables complete austenite reversion, producing a supersaturated solid solution. Scanning Electron Microscope (SEM) analysis confirmed elimination of non‐equilibrium features, while Energy Dispersive Spectrometer (EDS) revealed that this contributed to the enhanced strength and hardness in the as‐deposited material. Irregular carbide precipitates are identified as detrimental second phases that may initiate structural failure. These results establish clear correlations between heat treatment parameters, microstructural evolution, and mechanical degradation—particularly tensile strength reduction.