High-temperature oxidation performance and its mechanism of TiC/Inconel 625 composites prepared by laser metal deposition additive manufacturing

The laser metal deposition (LMD) additive manufacturing process was applied to produce TiC/Inconel 625 composite parts. The high-temperature oxidation performance of the LMD-processed parts and the underlying physical/chemical mechanisms were systematically studied. The incorporation of the TiC reinforcement in the Inconel 625 improved the oxidation resistance of the LMD-processed parts, and the improvement function became more significant with increasing the TiC addition from 2.5 wt. % to 5.0 wt. %. The mass gain after 100 h oxidation at 800 °C decreased from 1.4130 mg/cm2 for the LMD-processed Inconel 625 to 0.3233 mg/cm2 for the LMD-processed Inconel 625/5.0 wt. % TiC composites. The oxidized surface of the LMD-processed Inconel 625 parts was mainly consisted of Cr2O3. For the LMD-processed TiC/Inconel 625 composites, the oxidized surface was composed of Cr2O3 and TiO2. The incorporation of the TiC reinforcing particles favored the inherent grain refinement in the LMD-processed composites and, therefore, the composite parts possessed the sound surface integrity after oxidation compared with the Inconel 625 parts under the same oxidation conditions. The LMD-processed TiC/Inconel 625 composites exhibited the excellent oxidation resistance under the oxidation temperature of 800 °C. A further increase in the oxidation temperature to 1000 °C caused the severe oxidation attack on the composites, due to the unfavorable further oxidation of Cr2O3 to CrO3 at the elevated treatment temperatures.