In-situ reaction compositing behavior of the Ni62Ti38+C interlayer and its effects on interfacial microstructure and mechanical properties of the Cf/C-GH3044 joint

Leveraging the in-situ reactive composite formation characteristic between the Ni-Ti alloy and carbon, a novel joining process was proposed to address the high residual stress and poor heat-resistance encountered in C f /C-GH3044 joint. The powder-mixture of Ni 62 Ti 38 (at.%) eutectic alloy and carbon (C) was used as an interlayer. At joining temperature, the added C react with the melting-point depressant Ti in the liquid Ni-Ti to form TiC particles and initiates isothermal solidification of the Ni-matrix. The TiC subsequently react with W originating from the GH3044 superalloy to form (Ti,W)C-shelled TiC particles, namely (Ti,W)C@TiC. Thus, a (Ti,W)C@TiC-reinforced Ni-matrix composite joining layer was formed after joining. The (Ti,W)C@TiC endows the joining layer with a reduced CTE, alleviating the high residual thermal stress and improving the joint strength, while the Ni-matrix elevates the heat resistance of the joint. At the C f /C side interface, three distinct interfacial layers—Ni ss +C, Cr 3 C 2 , and (Ti,W)C—form in sequence. Both an insufficient Ni ss +C thickness and an excessive Cr 3 C 2 thickness are detrimental to the joint strength. An optimal C addition content can effectively thicken the Ni ss +C layer while suppress the formation of the continuous brittle Cr 3 C 2 layer. The shear strength of the joints at room temperature first increases and then decreases with increasing C addition, peaking at 32.1 MPa. The peaking strength is 2.7 times that of the C-free joint. Under the optimal C addition, the joint fracture occurs in the Ni ss +C layer and occasionally extends into the C f /C composite, accompanied by carbon fibers pull-out.