Microstructure and Formation Mechanism of Vanadium Carbide-Reinforced Iron-Matrix Composites Prepared by Solid-Phase Diffusion

Vanadium carbide-reinforced iron-matrix composites were produced via solid-phase dispersion method that included heat treatment at 1223, 1273, and 1323 K for different times. The vanadium carbide layers (V2C and V8C7 dense layers) were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and the Vickers hardness test. The kinetics of vanadium carbide layers were analyzed with an Arrhenius-type equation. The results showed that the vanadium carbide-reinforced iron-matrix composites consist of alpha-Fe, V2C, and V8C7 with an incomplete reaction of V. The thickness of the V2C and V8C7 dense layers ranged from 5.11 +/- 0.41 mu m to 17.43 +/- 1.43 mu m and from 16.30 +/- 1.52 mu m to 76.32 +/- 3.26 mu m, respectively, depending on the treatment time and temperature. The average micro-hardness of the vanadium carbide-reinforced iron-matrix composites varied according to the different zones: 1963 HV0.1 (V2C layer), 1707 HV0.1 (V8C7 dense layer), and 235 HV0.1 (matrix). The dynamics of the layers indicated that the layer thickness and the process time had a parabolic relationship. And the relationship demonstrated that pervasion had a strong impact on the layer covering.