Microstructure and mechanical strength of diffusion-bonded Ti3SiC2/Ni joints

Diffusion bonding of Ti3SiC2 and nickel has been conducted at temperatures of 800 degrees C-1100 degrees C for 10-90 min under 6-20 MPa in a vacuum. The phase composition and microstructure of the joints were investigated by x-ray diffraction, scanning electron microscopy, and electron probe microanalysis. The total diffusion path of the joining is determined to be Ni/Ni31Si12 + Ni16Ti6Si7 + TiCx/Ti3SiC2 + Ti2Ni + TiCx/Ti3SiC2. The growth of the reaction layer follows parabolic law, and the temperature dependence of the reaction constant, k, can be expressed as k = 1.68 x 10(-4) exp(-118 +/- 12 kJ/RT) m/s(1/2). The diffusion of nickel through the reaction zone toward Ti3SiC2 is the main controlling step in the bonding process. Joint strengths were determined through shear tests. The maximum shear strength of 121 +/- 7 MPa, which is close to the shear strength of Ti3SiC2, has been obtained under the condition of 1000 degrees C for 10 min under 20 MPa.