Low-temperature nitriding of nanocrystalline Inconel 718 alloy

- Nitriding efficiency was significantly increased in Inconel with UNSM pretreatment.
- M-phase was generated in Inconel after nitriding at 460 °C with UNSM pretreatment.
- Higher corrosion and wear resistance was observed in the UNSM + nitriding sample.

Surface severe plastic deformation was induced in Inconel 718 alloy using ultrasonic nanocrystal surface modification (UNSM). Low-temperature gas nitriding was carried out on non-processed and UNSM-processed Inconel 718 samples. The microstructure and material properties were characterized using X-ray diffraction, scanning electron microscopy, the Vickers hardness test, and wear and corrosion testing. The results demonstrated that gas nitriding efficiency was significantly enhanced by the UNSM treatment. Higher nitrogen concentration was observed in the surface layer of the UNSM samples. The nitride layer in the UNSM + nitriding sample exhibited an increased hardness over that of the nitriding sample and the UNSM treated sample. Additionally, both wear resistance and corrosion resistance were significantly improved in the UNSM + nitriding sample.