Joining of ZrB2‐Based Ultra‐High‐Temperature Ceramic Composites to Cu–Clad–Molybdenum for Advanced Aerospace Applications

Abstract

Three hot‐pressed ZrB2‐based ultra‐high‐temperature ceramic composites (UHTCC), ZrB2–SiCp(ZS), ZrB2–SiCp–C (ZSC), and ZrB2–SCS9A (SiC fiber)–SiCp(ZSS), were joined to Cu–clad–Mo using AgCuTi brazes (TL∼1073–1173K) and Pd‐base brazes (TL∼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 αCu–clad–Mo<αZS(α=coefficients of thermal expansion). Above this thickness, αCu–clad–Mo>αZS, 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.