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

Beryllium was successfully bonded to a Reduced Activation Ferritic Martensitic (RAFM) steel with a maximum strength of 150 MPa in tension and 168 MPa in shear. These strengths were achieved using Hot Isostatic Pressing (HIP), at temperatures between 700 °C and 750 °C for 2 h and under a pressure of 103 MPa. To obtain these strengths, 10 μm of titanium and 20 μm 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.