Oxidation inhibition behaviors of HfB <sub>2</sub> ‐MoSi <sub>2</sub> ‐SiC oxygen blocking coating prepared by spark plasma sintering
Qingqing Yang, Xuanru Ren, Menglin Zhang, Lu Zhu, Hongao Chu, Peizhong Feng
Abstract
Abstract The HfB 2 ‐MoSi 2 ‐SiC oxygen blocking coatings were prepared by the spark plasma sintering (SPS) technique, whose oxidation inhibition ability was further strengthened by the pre‐oxidation treatment. The effect of MoSi 2 content and pre‐oxidation treatment process on the oxygen blocking ability of the HfB 2 ‐MoSi 2 ‐SiC coating at 1973 K were conducted. After SPS, for the HfB 2 ‐MoSi 2 ‐SiC coatings with 20 wt%, 40 wt%, and 60 wt% MoSi 2 , the relative density of the coatings are 92.6%, 93.9%, and 85.6%, respectively. Owing to the enhanced compactness of the coatings, increasing MoSi 2 content can significantly improve the protection efficiency of the coatings during the activation oxidation stage. However, due to the increased formation of gaseous by‐products during the inerting oxidation stage, excessive MoSi 2 weaken the oxidation inhibition ability of the coatings. The sufficient dispersion of Hf‐oxides nanocrystals in the glass layer conduces to enhance the oxygen blocking ability of the glass layer, making the 40HfB 2 ‐40MoSi 2 ‐20SiC coating present the best oxidation protective ability. The pre‐oxidation treatment at 1773 K conduces to form the steady glass layer with fewer defects at the cost of a lower oxidation consumption of the coating, which enhanced the protection efficiency of the coating from 96.9% to 99.8% and reduced the oxygen permeability from 0.13% to 0.028%.