Calculating the interdiffusion coefficient in TaC/VC diffusion couple and investigation of solid solution formation and mechanical properties

Abstract

Owing to high-temperature melting and high hardness besides the mutual solubility, TaC-VC binary system is being developed to apply in aggressive and high-temperature environments. This research aims to investigate the solid solution formation of the TaC-VC binary system as well as calculate their diffusion coefficient in each other by the Boltzmann-Matano method. So, three compositions of the TaC-XVC binary system (X = 25, 50, and 75 mol%), as well as a TaC/VC diffusion couple sample, were sintered at 1850 °C for 20 min at 40 MPa pressure via spark plasma sintering (SPS) technique. It was found the maximum relative density and hardness values of 98.1 % and 24.6 GPa were obtained for the TaC-75 mol% VC composite specimen. A slight increment in fracture toughness was observed from 50 to 75 mol% VC and reached 4.7 MPa m0.5 in the TaC-75 mol% VC sample. The XRD results showed V diffuses to TaC crystal lattice and creates (TaXV1−X)C solid solution in TaC containing 25 and 50 mol% VC while in TaC-75 mol% VC, dominantly Ta diffuses in VC and (VXTa1−X)C solid solution is formed. Finally, the interdiffusion coefficients of V into TaC and Ta into VC lattice were calculated as 3.4 * 10−10 cm2 s−1 and 1.3 * 10−10 cm2 s −1, respectively by SEM/EDS analyses in the TaC/VC diffusion couple sample.