Evaluation of diffusion behavior and mechanical characteristics in the ZrC-NbC pseudo-binary system

Accurate information on diffusion kinetics and mechanical characteristics for the ZrC-NbC pseudo-binary system is essential for developing high-performance ZrC-based alloys. At present work, we have employed the diffusion couple method to investigate systematically the diffusion kinetics of the ZrC-NbC pseudo-binary system in the temperature range of 1373–1673 K. The mechanical characteristics of the diffusion region have been studied by the nanoindentation technique. Evaluations have been conducted on the impurity diffusion and inter-diffusion coefficients of the ZrC-NbC pseudo-binary system. As Nb concentration increases, the inter-diffusion coefficients of the ZrC-NbC pseudo-binary system decline. The inter-diffusion activation energies of the ZrC-NbC pseudo-binary system increase as Nb concentration increases, with the largest value of 395.3 kJ/mol at 55 at. % Nb concentration. The impurity diffusion activation energies of C in ZrC, C in NbC, Nb in ZrC, and Zr in NbC are 242.4 kJ/mol, 167.9 kJ/mol, 388.3 kJ/mol, and 288.0 kJ/mol, respectively. The Vickers hardness and Young's modulus of Zr1-xNbxC have also been measured, with the highest values of 29.4 ± 2.7 GPa and 650.7 ± 12.9 GPa, respectively. With an increase of Nb concentration, Young's modulus of Zr1-xNbxC increases, while its Vickers hardness first increases and subsequently declines. The results of this study could be advantageous to develop ZrC-based alloys and improve their properties.