Fusion energy systems and other applications need radically improved brazed graphite-metal joints to withstand a severe plasma environment. Present brazing methods produce joints that are neither reliably strong, cost-effective, vacuum tight, nor thermomechanically shock resistant. These joints lack the proper composition profiles near the bonding interfaces to absorb and withstand unavoidable mismatch stresses between the graphite and metal substrate. One solution to these problems is to microengineer the critical interfacial bonding regions. This project will perform this microengineering using proprietary and commercially successful W/Mo-based melt-metallizing and brazing methods. When made by these methods, even "unmatched" end-to-end joints of square A1203 rods to carbon steel rods survived over 12 repeated rapid thermal cycles between 1,000øC and OøC ice water. A unique, low cost, low temperature but high yielding method for mass production of top quality brazed graphite joints will be developed for widespread uses in government and industry. During Phase I, fractional factorial experiments will be made to study systematically metallizing composition, temperature, time, and ambient gas for proving the feasibility of these joints, which have liquid-diffusion graded, interfacial regions, with adherent, tough, and readily wetted metallized surface layers.Anticipated Results/Potential Commercial Applications as described by the awardee:In Phases II and III, the method described will be used to produce inexpensive, strong, vacuum tight, and thermally shock-resistant brazed graphite joints for various uses by the government and private industry
