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, approximately 50 kHz, 1000-1150 °C, a 5 min hold, and approximately 1 × 10⁻³ Torr. Relative density, Vickers hardness, maximum compressive stress, microstructure, and corrosion behavior in 3.5 wt% NaCl were evaluated. Relative density increased from 88.87% at 1000 °C to 98.61% at 1150 °C. Hardness measurements increased from 156.5 ± 5.2 HV10 to 263.0 ± 14.4 HV10, while the measured maximum compressive stress increased from 284 to 379 MPa. Fiji-based image analysis showed decreasing pore-area fraction, pore size, and pore connectivity, together with increasing pore circularity and grain size. The lowest polarization-derived corrosion rate was obtained at 1100 °C, whereas the 1150 °C specimen had the highest density and a comparatively clean post-corrosion surface. Within the investigated conditions, the results indicate that direct HFIHS can consolidate 316 L stainless steel to near-full density within a short processing cycle and at substantially lower applied pressure than the conventional press-and-sinter baseline used for comparison.