Diffusion bonding beryllium to Reduced Activation Ferritic Martensitic steel: Development of processes and techniques

► We diffusion bonded Be to Reduced Activation Ferritic Martensitic steel. ► Thin copper and titanium interlayers improved the bond's shear strength to 168MPa. ► A slow cooling scheme and intermediate hold step greatly increased bond strength. ► Failure occurred in Be–Ti and Cu–Ti intermetallic compounds. Beryllium was successfully bonded to a Reduced Activation Ferritic Martensitic (RAFM) steel with a maximum strength of 150MPa in tension and 168MPa in shear. These strengths were achieved using Hot Isostatic Pressing (HIP), at temperatures between 700°C and 750°C for 2h and under a pressure of 103MPa. To obtain these strengths, 10μm of titanium and 20μm of copper were deposited on the beryllium substrate prior to HIP bonding. The copper film acted a bonding aid to the RAFM steel, while the titanium acted as a diffusion barrier between the copper and the beryllium, suppressing the formation of brittle intermetallics that are known to compromise mechanical performance. Slow cooling from the peak HIP temperature along with an imposed hold time at 450°C further enhanced the final mechanical strength of the bond.