Joining of ZrB_2-Based Ultra-High-Temperature Ceramic Composites to Cu-Clad-Molybdenum for Advanced Aerospace Applications

摘要

Three hot-pressed ZrB_2-based ultra-high-temperature ceramic composites (UHTCC), ZrB_2-SiC_p (ZS), ZrB_2-SiC_p-C (ZSC), and ZrB_2-SCS9A (SiC fiber)-SiC_p (ZSS), were joined to Cu-clad-Mo using AgCuTi brazes (T_L ～ 1073-1173K) and Pd-base brazes (t_L～ 1493—1513K). More extensive chemical interactions occurred in Pd-base joints than in AgCuTi-base joints. The Pd-braze region displayed higher hardness in joints made using ZS than ZSS and ZSC. Residual stress calculations point toward negative strain energy up to ～23% clad layer thickness because α_(Cu-clad-Mo) < α_(ZS) (α = coefficients of thermal expansion). Above this thickness, α_(Cu-clad-Mo) < α_(ZS) strain energy is positive, and it increases with increasing thickness. Projected reductions in the thermal resistance highlight the benefits of joining the UHTCC to Cu-clad-Mo.