High-frequency induction heat sintering of 316L stainless steel: a systematic investigation of ultra-low-pressure processing, microstructure, and corrosion performance

The present work provides a systematic evaluation of direct pressure-assisted High-Frequency Induction Heat Sintering (HFIHS) of gas-atomized 316 L stainless steel powder at 40 MPa and approximately 50 kHz, across a temperature range of 1000–1150 °C, with a 5 min hold at approximately 1 × 10⁻³ Torr. This study investigates the relative density, Vickers hardness, maximum compressive stress, microstructure, and corrosion behavior in a 3.5 wt% NaCl solution. Results indicated that relative density progressed from 88.87% at 1000 °C to 98.61% at 1150 °C. Hardness measurements enhanced significantly from 156.5 ± 5.2 HV10 to 263.0 ± 14.4 HV10, while maximum compressive stress rose from 284 to 379 MPa. Image analysis using Fiji software demonstrated reductions in pore-area fraction, pore size, and pore connectivity, alongside increases in pore circularity and grain size. Notably, the most favorable corrosion rate occurred at 1100 °C, whereas the specimen at 1150 °C exhibited the highest density and a relatively clean post-corrosion surface. Overall, findings suggest that direct HFIHS can effectively consolidate 316 L stainless steel to near-full density within a brief processing duration and at significantly lower applied pressure compared to the traditional press-and-sinter approach.