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 μm/s for GSIC and −0.3 mg/s and −0.53 μm/s for GZSIC specimens, respectively. The average linear ablation rate of the GZSIC specimen was decreased by ~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.