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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. [ABSTRACT FROM AUTHOR]

The effects of Ultrasonic Nanocrystal Surface Modification (UNSM) on the thermal oxidation (TO) behavior of Ti6Al4V alloy has been investigated. The thermal oxidation was carried out at 500, 600 and 700 °C. The microstructure after UNSM and TO was characterized using scanning electron microscopy with energy dispersive spectroscopy. And phase identification was performed using X-ray diffraction. At 500 and 600 °C, the reaction capability are enhanced and the oxidation layer thickness is increased in the UNSM-treated Ti6Al4V alloy. This is attributed to nanoscale grain boundaries created by UNSM that serve as efficient diffusivity paths for interstitial gaseous atoms. When the TO temperature rises to 700 °C, due to dislocation elimination and grain coarsening induced by the high temperature, the oxidation layer thickness of the Ti6Al4V specimens show no significant difference. [ABSTRACT FROM AUTHOR]