Interdiffusion kinetics and solid-state reaction mechanism between Cr2O3 and calcium ferrite based on diffusion couple method

Abstract The presence of Cr2O3 was found to reduce the quality of sinter from high-chromium vanadium-titanium magnetite obtained by a blast furnace-basic oxygen furnace process. The kinetics and reaction mechanism of the solid-state reaction between Cr2O3 and calcium ferrite (CF) were studied by a diffusion couple method. The phase of the product and the change in the concentration of Ca and Cr across the diffusion layers were analyzed by scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS). Based on the concentration profile of Cr element, the interdiffusion coefficient in different stages of the Cr2O3-calcium ferrite system which were affected by temperature and atmosphere were calculated by the Wagner method. The results indicated that the interdiffusion coefficient increases from 1373 K to 1473 K. The interdiffusion coefficient in the diffusion product (CaCr2O4) layer was the largest. At 1373-1473 K, the interdiffusion coefficient of the system was in the order of 10-12~10-10 cm2/s in air. The diffusion activation energy ED in air ranged from 25.78 kJ/mol to 123.26 kJ/mol.The thickness of the product layer and the interdiffusion coefficient in N2 were smaller than those in air. A hypothesis in which oxygen participates in the mass transfer is proposed.