Microstructure And Properties Of Diffusion Bonded Joints Between Tungsten And Steel Using A Interlayer

Tungsten is one of the most promising Plasma Facing Materials, and stainless steel is an important structural material. Due to their excellent physical and mechanical properties, the research on bonding tungsten and steel will have significant application values in national defense and nuclear industry. However, tungsten is incompatible with steel, as well as the thermal expansion coefficient between the two alloys is obvious different, which will lead to a quite high thermal stress during connecting and being serviced, resulting in the failure of the materials. Therefore, an interlayer is usually necessary to reduce the residual stress and prolong joint’s service life. Diffusion bonding is an effective method to get high-performance joint of dissimilar materials. But the suitable interlayer is the key to get a high-performance tungsten/steel joint.In the present work, V, V+Ni, and Ni-Fe cladding layer were used as the interlayer, and the microstructure, properties as well as the related mechanism of the diffusion Bonded Joints between tungsten and steel with interlayer were systemic investigated. The results indicate that:1) A reliable bonding between tungsten and steel could be obtained by using vanadium interlayer. The W/V/steel joint consisted of a V(W) solid solution layer, a residual V interlayer, a VC layer and a decarburized layer of steel matrix. V/steel interface of W/steel joints was the main fracture source.2) A reliable bonding between tungsten and steel could be obtained by using vanadium/nickel composite interlayer. The W/steel joint consisted of a V(W) solid solution layer, a residual V interlayer, a VC layer, a mixing layer of VC and Ni-V intermetallics, a Ni-V intermetallics layer, a residual Ni interlayer and a Ni-Fe solid solution layer. The tensile strength of joint was reached to164MPa and the bonded samples fractured through the V/Ni interface.3) In surface of tungsten, the typical W-Ni-Fe alloys with microstructure graded distribution was formed by cladding experiment. A reliable bonding between W and steel could be obtained by using Ni-Fe cladding layer. The fracture took place inside the tungsten near the interface.