Joining of C/C composite with high entropy alloy interlayers via spark plasma sintering and its mechanical strength at 1600 °C

A novel method is developed to join C/C composites via spark plasma sintering (SPS) using ZrHfNbTa and TiZrHfTa high entropy alloys as interlayers. The joint microstructure, interface reaction and shear strength at 1600 degrees C were investigated. For both interlayers, the C/C joint consisted of a single high entropy carbide phase. However, the use of different high entropy alloy interlayers resulted in differences in the micro-homogeneity of the formed high entropy carbide as well as the thickness of the joint zone. Both formed (Zr-Hf-Nb-Ta)C and (Ti-Zr-Hf-Ta)C high entropy carbides, which were homogeneous on the atomic scale, and no impurities were found at the grain boundaries. The shear strengths of the C/C-ZrHfNbTa-C/C joint and C/C-TiZrHfTa-C/C joint at 1600 degrees C were comparable, with values of 23.5 +/- 1.2 MPa and 24.6 +/- 2.5 MPa, respectively, which are more than twice the shear strength obtained with pure Ti foil (11.6 +/- 3.6 MPa).