The High Temperature Thermal Shock Performance of Si-Ti-Cr Silicide System Coating on Nb-Hf Alloy Surface in Atmosphere and Vacuum

To improve the high-temperature oxidization resistance, the Si-Ti-Cr silicide coatings were fabricated on Nb-Hf (NbHf 10-1) alloy by slurry sintering and high-temperature permeation. The high temperature thermal shock performance of Si-Ti-Cr silicide coated Nb-Hf alloy samples in atmosphere and vacuum was comparatively characterized. The failure mechanism of Si-Ti-Cr coating in vacuum and air after thermal shock test was determined by simulating the temperature and thermal stress distribution of the coating during thermal shock. The results show that silicide coating exhibits excellent thermal shock resistance below 1300°C in vacuum. The weight loss rate of the coating is less than 0.8 mg/cm2 after 100 cycles at 1300°C. The thermal shock life of the coating in the atmosphere decreases with the increase of temperature. Below 1450°C, the coating mass increases gradually without falling off, and the weight gain rate is less than 3 mg/cm2