Depositing WC particle coating via SMNAT contributes to a high-quality Ti2AlNb/TA2 joint of diffusion bonding at low temperature.

To avoid loss in mechanical property and reduce the production cost of the matrix titanium and Ti2AlNb-based alloys, lowering the temperature of the diffusion bonding is challenging research worth studying. In this work, surface mechanical nano-alloying treatment is applied to the TA2 titanium and Ti2AlNb-based alloy to deposit a coating of WC and W phases particles as a gain interlayer. Deposited and removal-deposit samples are respectively diffusion-bonded into the dissimilar alloy joints at a low temperature of 800 °C for 1 h under the pressure of 10 MPa. The microstructure, surface morphology, and element and phase compositions of the deposit on the surface and on the interface of the joints were investigated. The dynamic transformation of the deposited phase is discussed in detail. The phase transformations from WC to W and from WC or W to TiW occur during the deposit and diffusion bonding, respectively. The joint, boned with deposited samples, presents an 11.5% higher shear strength than the joint boned with removal-deposit samples. The detailed discussion suggests that the deposited phases and their corresponding phase transformation products present a nanograin characteristic during and after the diffusion bonding process that would promote the atoms' diffusion and strengthen the bonded joint. The present findings provide a new strategy for obtaining high-mechanical performance joint of diffusion bonding through a specific nano-alloying deposit coating. • An approach for fabricating high-quality DB joints using nano-alloying coating by SMNAT was first proposed. • Tungsten carbide (tungsten) coatings were prepared on TA2 titanium and Ti2AlNb alloy by SMNAT. • Phase transformation occurs from the WC to the W, and from the WC to the TiW during the SMNAT and DB process respectively. • Nano TiW and WC grains in the deposit promote the atoms' diffusion on the interface. • Ultra-fined particles with nano TiW and WC grains strengthen the DB joints. [ABSTRACT FROM AUTHOR]