Development of SiC-ZrC-based ultra-high temperature ceramic coatings via composite method of polymer precursor pyrolysis plus gaseous reactive infiltration

SiC-ZrC-based composite coatings on carbon/carbon composites via ZrC polymer precursor pyrolysis (PPP) plus gaseous reactive infiltration (GRI) of Si or ZrSi2, separately denoted as GSIC and GZSIC, were comparatively studied to explore the feasibility and effectiveness of GRI of ZrSi2. This composite method by applying ZrSi2 or Si was proven to similarly produce dense coatings with enhanced coating/substrate interfacial bonding strength for the formed zig-zag transition layer. Furthermore, the GRI of ZrSi2 instead of Si further increased the UHTC (ZrC) content in the as-deposited coatings resulted from the reaction of infiltrated ZrSi2 and pre-introduced graphite, enhancing the ablation resistance of the coatings for carbon/carbon composites due to the formed stable Zr-rich Zr-Si-O multiphase oxide. The average mass and linear ablation rates were-0.12 mg/s and 1.56 mu m/s for GSIC and-0.3 mg/s and-0.53 mu m/s for GZSIC specimens, respectively. The average linear ablation rate of the GZSIC specimen was decreased by similar to 134% when compared to the GSIC specimen. These results further indicate that the PPP + GRI method with metal silicide MeSi2 (Me = Zr, Ti, Hf, Cr, etc.) will contribute to the optimal fabrication of dense composite coatings with controllable microstructure, adequate evenly-distributed ultra-high temperature ceramic (UHTC) phases, enhanced interfacial bonding strength and wide circumstance suitability for potential applications. The related work is ongoing in our laboratory.