Effective Anti-Oxidation Repair Coating for C/C Brake Materials Comprising Lead-Borosilicate and Bismuth-Borosilicate Glass

To achieve effective antioxidation of on-site repair coating for C/C brake materials in the full temperature range (500–900 °C), lead glass and bismuth glass were introduced into the borosilicate glass to acquire the protective coatings. Before preparing coating samples, the thermal gravity characteristics of the lead/bismuth–borosilicate glass powders were analyzed by TG/DSC. The results revealed that the temperature at which weight gain begins was 495 °C and 545 °C, respectively. The oxidation behaviors of the lead- and bismuth-modified borosilicate glass coatings were compared at 500 °C, and the antioxidation properties of the former were further examined from 500 to 900 °C. The oxidation results indicated that mixing lead glass with borosilicate glass realized effective oxidation resistance in the full temperature range. With a lead content of 20%, the lead–borosilicate glass coating was able to protect C/C substrates from oxidation. The corresponding weight loss of the lead-glass-coated samples was −1.89% when oxidized at 500 °C for 10 h, while the weight loss was −2.55% when further oxidized at 900 °C for 10 h. However, mixing bismuth glass with borosilicate glass was difficult to achieve the oxidation resistance of the coating at 500 °C due to the significant phase separation.