Effect of Mo on interdifussion behaviors and interfacial characteristics in multicomponent diffusion couple of FeCoCrNi high entropy alloys and diamond

Abstract

A multi-component diffusion couple of diamond/Mo/FeCoCrNi HEA composite structure was designed and fabricated, and the refractory metal Mo was introduced to construct a diffusion barrier between diamond and HEA. The interfacial diffusion and microstructural evolution of the diffusion couple were studied. The results indicated that, after diffusion, the Diamond/HEA composite structure formed equiaxed Cr-rich σ phase and polycrystal graphite at interface. In contrast, the Diamond/Mo/HEA composite structure formed Mo-rich μ phase at the interface. The graphitization in Diamond/Mo/HEA was significantly reduced compared to the Diamond/HEA composite structure. Due to the low solubility of Fe, Co and Ni in μ phase, and the low interdifussion coefficient of Co, Ni in Mo, the Mo layer was manifested as an effective diffusion barrier against the diffusion of HEA into the diamond. Moreover, the metallurgical bonding with high interfacial bonding strength was formed at the interface of the composite structures due to the semi-coherent interface and incoherent interface in Diamond/HEA and Diamond/Mo/HEA, respectively.