Effect of transient liquid phase (TLP) bonding on the ductility of a Ni-base single crystal superalloy in a stress rupture test

A Ni-base single crystal superalloy was transient liquid phase (TLP) bonded using a Ni–Cr–B amorphous foil at 1230 °C for 8 h. Stress rupture tests of the TLP joint and a matrix sample were carried out at 982 °C/248 MPa and 1010 °C/248 MPa. The microstructures and fracture surfaces were studied using scanning electron microscopy (SEM). Transmission electron microscopy (TEM) investigations were performed after creep rupture testing to examine the deformation substructures. The results show that the stress rupture ductility of TLP joints is significantly decreased compared to the matrix sample. This reduction of the ductility of TLP joints can be attributed to solid solution strengthening by boron atoms, subgrain boundaries formed in the bonding zone and the concentration of creep cavities formed during the last stage of the stress rupture test.