Liquid phase diffusion bonding of ReneSO using pure boron

Pure boron (B) has been applied to the liquid phase diffusion bonding of Ni-base superalloy, ReneSO, as an intermediate layer, considering that B has very high diffusivity in Ni and Ni-B system forms eutectic point much lower than their melting points. ReneSO could be bonded well through the liquid phase diffusion bonding with the intermediate layer of pure B. During isothermal solidification, the width of eutectic layer, i.e. liquid layer at bonding temperature, was given by a linear function of square root of holding time. Bonding time of the Rene80/B/Rene80 joint was much short, and it took 4.8 ks for isothermal solidification and homogenization. But, when bonding time was too short or intermediate material was thick, boride of (Cr, Mo, W, M);B, was produced along the bonded line, where M means minor elements Ni, Ti and Co. Bonded joint was slightly hardened after bonding due to increase of B. Tensile strength of the Rene80/B/Rene80 joint at 1144 K (1600F) was obtained up to 567 MPa, and it was 90% of base metal.