Applicability of ultra-fast laser machining process and microstructure evolution mechanism of ultra-high temperature ceramic matrix composites

The high brittleness of the ceramic matrix and the high deformability of the carbon fibers pose a challenge for the machining of carbon fiber reinforced ultra-high temperature ceramic (C_f/UHTCs) matrix composites. In this study, C_f/ZrB₂-SiC UHTCs are processed by ultra-fast laser to investigate the ablation mechanism, and the ablation thresholds are calculated separately for different parts of the material. Excessive laser energy or repetition frequency will lead to the ablation mechanism changing from photochemical to photothermal. For ceramic matrix, SiC is preferentially removed during machining, followed by the removal of high-density and high melting point ZrB₂. Large amounts of vaporized ZrB₂ with the ZrO₂ melt will form spherical particles. Raman spectroscopy analysis show that with increasing laser energy input, the temperature of carbon fiber increases, and the structural ordering and graphitization degree of the carbon material increased.