Application of response surface method (RSM) to investigate the effects of process parameters on the microstructure and shear strength of TZM/graphite joints bonded by using spark plasma sintering

Abstract

The joint of TZM/graphite with Ti foil as the interlayer was successfully obtained by using gradient sintering process of spark plasma sintering (SPS). The response surface method (RSM) based on Box-Behnken design was applied to statistically specify the effects of the bonding temperature (T), bonding pressure (P), holding time (t) and thickness of the interlayer (h) on the shear strength of TZM/graphite joint. The optimum process parameters of T = 1450 °C, P = 17.2 MPa, t = 0.8 h and h = 109 μm were performed to obtain the highest shear strength of 53.6 MPa, which demonstrated the RSM was an excellent tool to implement and tailor the shear strength of the TZM/graphite joint. The excellent shear strength can be ascribed to (βTi, Mo) solid solution crossing each other at the interface, formation of finger-like TiC and little defect in the joint. The stress concentration at the interface between graphite and the TiC layer was evidently larger than that between (βTi, Mo) solid solution and TZM, which led to the occurrence of the shear fracture in the region of TiC phase.