Formation mechanism of the TiN containing coating on the Al2O3-Ti2O3 composite at 1400°C nitrogen-blowing

Abstract

The Al2O3-Ti2O3 composite is a byproduct of smelting ferrotitanium alloy, and a gold coating material was successfully obtained by nitriding this raw material at 1400 °C for 3h. The material was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, thermal gravimetry and differential scanning calorimetry (TG-DSC) and vibrating sample magnetometry (VSM). The formation of TiN containing coating layer on the surface of the material was confirmed by XRD and Raman spectroscopy analysis. The golden surface disappeared after polishing by cross-section polishing, and the titanium compounds in the material after nitriding showed a gradient distribution from the surface to the inside as TiN→Ti3O5→Ti2O3. From SEM analysis, titanium nitride was observed to be obtained by a gas-solid reaction with cluster growth, and the thickness of titanium nitride was approximately 10 μm. The main reaction in the nitridation process was determined by TG-DSC as well as thermodynamic analysis. The sample maintained a uniform mass increase from 665 °C to 1430 °C, and the Ti2O3 on the surface of the sample underwent both nitridation and oxidation. The hysteresis of the sample as a composite was complex before nitriding, and behaved as a soft magnetic material after nitriding, indicating the macroscopic scale coating uniformity of the samples.