Thermochemical erosion of hafnium carbide modified carbon/carbon composite throat in a small solid rocket motor

Thermochemical erosion of hafnium carbide (HfC) modified carbon/carbon (C/C) composite throat was investigated using a hot-fire testing system in a small solid rocket motor. Chemical composition of the equilibrium combustion products was calculated by NASA-CEA program based on the principle of free energy minimum. The reaction products between the oxidizing species and HfC in the C/C composites were also calculated by FactSage. The results show that H₂O, CO₂, and OH are the main oxidizing species to consume carbon and HfC and generate thermochemical erosion to the throat materials. The interface of the fibers and matrix is preferentially ablated, and then erosion extends to the fibers and matrix. The formation of cone-shaped fibers and shell-shaped matrix is attributed to the thermochemical erosion of the flame.