Thread Content
Considering the high-temperature applications of silicon carbide coatings mentioned earlier, it has the following clear performance limitations in extreme high-temperature environments: high-temperature oxidation failure. In oxygen-containing environments at temperatures above 1200°C, SiC undergoes intense oxidation reactions to form SiO₂; when the temperature exceeds 1600°C, the SiO₂ layer begins to volatilize, losing its protective function. As a result, the coating continues to be oxidized and thinned, with an erosion rate of up to 1.2 mm per month in corrosive atmospheres containing substances such as Cl₂. Thermal shock and interfacial mismatch: If there is a large difference in the thermal expansion coefficients between the coating and the substrate, stress continues to build up at the interface during repeated heating and cooling cycles above 1300°C. This eventually leads to the formation of microcracks, bubbling of the coating, or even local delamination, thereby rendering it unable to provide protection. High-temperature creep and performance degradation: When operating at temperatures above 1400°C for extended periods, the glassy phase at the grain boundaries of the coating gradually softens, resulting in a sharp increase in the creep rate. Under conditions of 1500°C and 100 MPa stress, the creep displacement in some systems can reach 1.2 mm after 1000 hours, which far exceeds the allowable threshold under normal operating conditions. Performance degradation in special environments: In a neutron irradiation environment at temperatures above 650°C, the coating is prone to radiation-induced microcracks, with a peeling rate that can reach up to 20% ； In a high-temperature hydrogen environment, grain boundary hydrogen embrittlement also occurs, leading to a significant decrease in the strength and toughness of the coating.