Improvement in mechanical properties of transient liquid phase (TLP) bonded joints of HP alloy at the elevated temperature was investigated employing newly developed insert metal. TLP-bonding was carried out at 1403-1463 K for 600s in vacuum. The chemical compositions of insert metal were optimized by the mathematical programming method. The objective function which was introduced as an index of performance of insert metals involved the melting point of insert metal, the strength (hardness) and formability of microconstituents in the bonding layer as the evaluating factors. A composition of Ni-3% Cr-4% Si-3% B which optimized the objective function was determined. SEM observation revealed that the microstructure in bonding layer using the newly developed insert metal indicated a sound morphology without forming microconstituents such as Cr7 (C, B)3. The tensile properties of joint at 1273 K were comparable to those of base metal in the bonding temperature range of 1423-1463 K. The fractured of the joints bonded at 1423-1463 K occurred in the base metal substrate, while the joint bonded at 1403 K, which tensile properties were fairly deteriorated compared with the base metal, fractured at the bonding interface.
