Abstract
A ZrC–SiC inner layer was fabricated on carbon/carbon composites by pack cementation at different temperatures, aiming to prepare a transition layer for subsequent deposition of SiC and ZrC–SiC layer by chemical vapor deposition and plasma spray. Results show that the structure and phase composition of the inner layer significantly affected the interface bonding strength and thermal shock resistance of the multilayer, which played a vital role in resisting ablation. The jagged and porous surface of the inner layer led to forming a root-like pinning interface, generating a sawtooth combination between the layers. Moreover, the inner layer with high SiC content decreased the coefficient of thermal expansion mismatch between the inner and outer layers. Therefore, the enhanced ablation resistance of the optimum coating was attributed to the improved interface bonding strength and thermal shock resistance caused by the ZrC–SiC inner layer with rough and porous surface structure.
Highlights
Carbon/carbon (C/C) composites are potential candidates for structural materials at elevated temperature aerospace owing to their low-density, high specific strength and outstanding high-temperature properties [1,2,3]
It is crucial to prepare coating on C/C composites to improve their ablation resistance in complex high-temperature conditions
It is well known that ultra-high-temperature ceramics (UHTCs), such as ZrC + SiC and ZrB2 + SiC, can effectively enhance ablation resistance of C/C composites for the synergic effect of both components [7,8,9]
Summary
Carbon/carbon (C/C) composites are potential candidates for structural materials at elevated temperature aerospace owing to their low-density, high specific strength and outstanding high-temperature properties [1,2,3]. The coefficient of themal expansions (CTEs, namely, geometric characteristics regularly change with temperature under the thermal expansion and cold contraction processing), mismatches between the C/C composites matrix and UHTC outer layer can evoke thermal stresses in the coating, leading to the propagation of penetrability cracks and failure of the multilayer coating. To address this issue above, some research has been done to improve coating adhesion by means of pre or posttreatment processes focusing on ameliorating the stresses and increasing the coating hardness [10,11,12]. Based on the preparation of the inner layers with different microstructure and phases, effects of the ZrC–SiC inner layer on microstructure, ablation resistance, and mechanism of SiC/ZrC–SiC-coated C/C composites were investigated
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