Bonding performance and mechanism of a heat-resistant composite precursor adhesive (RT-1000∘C) for TC4 titanium alloy

Abstract

To facilitate the repairing and connecting processes for the non-main bearing TC4 alloy, a high-temperature (up to 1000[Formula: see text]C) resistant adhesive that is converted to the composite of intermetallics and ceramics is prepared. The composition evolution of the adhesive, the structure changes in the bonding layer, the reaction process at interfaces and the fracture mode of joints are comprehensively studied to explore its bonding mechanism. The results show that chemical bonding mechanism based on the formation of Ti5Si3 plays a critical role at 600[Formula: see text]C, and acts as the crucial one at elevated temperatures. As the reaction interlayer (2–5[Formula: see text][Formula: see text]m) is far thinner than the entire bonding layer (60–70[Formula: see text][Formula: see text]m), mechanical properties of the adhesive dominate the bonding performance, which is tied up with the composition and structure evolution. The differ of coefficient of thermal expansion (CTE) between the adhesive and the substrate remains lower than [Formula: see text][Formula: see text]K[Formula: see text] in range of 500–1000[Formula: see text]C. Specifically, the formation of composites from intermetallics and ceramics improves the mechanical properties and heat-resistant of the adhesive. The bonding strength reaches [Formula: see text]40[Formula: see text]MPa after pre-treatment at 1000[Formula: see text]C without pressure, and remains over 30[Formula: see text]MPa within the normal operating temperature range of 500–700[Formula: see text]C.