Vanadium carbide coating was obtained on the surface of AISI D2 steel by thermal reactive diffusion process using molten borax as based salt and vanadium pentoxide as vanadium donor. The process was performed at 900 °C, 940 °C, 980 °C and 1020 °C for 3 h, 4 h, 5 h and 6 h. The Optical Microscopy was used to observe the morphology of cross section of coating layer. Energy Dispersive Spectroscopy was used to analyse the element content of the matrix and the coating layer by spot scanning and line scanning. X-ray Diffraction was used to obtained the phase composition of the coating layer. Microhardness Tester was used to measure the Vickers hardness of the coating layer and matrix. Friction and wear tester were used to explore wear resistance of the coated and uncoated specimens. The results show that the thickness of vanadium carbide coating ranges from 7.54 μm to 19.1 μm under different treatment time and temperatures. The V8C7 and VC x are the main phases contained in the vanadium coating layer. A thickness of about 3 μm transition layer is between the matrix and coating layer and the transition layer has a block effect on the diffusion of iron. The growth rate constants of vanadium carbide coating layer at 900 °C, 940 °C, 980 °C and 1020 °C were obtained as (5.20 ± 0.116) ×10–11 cm2 s−1, (8.91 ± 0.253) ×10–11 cm2 s−1, (1.26 ± 0.020) ×10–10 cm2 s−1, and (1.70 ± 0.036) ×10–10 cm2 s−1 respectively. The activation energy for vanadium carbide layer is 123.3 ± 10.1 kJ mol−1 and the diffusion constant is (2.58 ± 1.96) ×10–5 cm2 s−1. The maximum hardness of vanadium carbide coating layer on the surface of AISI D2 steel can reach 2594HV. The wear rate of untreated and treated specimens was evaluated as 15.58 × 10–13 m3/(N·m), 5.63 × 10–13 m3/(N·m) respectively and the wear resistance of treated specimens by TRD process was about 3 times than untreated specimens.

By means of thermal analysis, specific heat values of sinter with different temperatures are measured and the linear function which along with the change of temperature is got. According to the actual condition, the porous medium model which describes the cooling process is established. The influences on cooling process of specific heat with fixed and variational values are compared. With the variational specific heat, the effects on cooling process of sinter initial temperature and air temperature are discussed. The result shows that both increasing sinter initial temperature and cold air temperature can improve the exhaust heat utilization, but the later delay the cooling time.

A new sintering method which considering the heat storage in iron ore sintering processis put forward in this paper.By means of thermal analysis, the kinetic properties of sintering burden with different proportion of coke are studiedand a few kinds ofreaction models are discussed by the liner correlation calculation.The results suggest that the oxidizingdecomposition of sintering burden can be described as a first - order chemistry reaction.Activation energies of three different sintering burdenswith different proportion of solid fuelare determined in this paper,thus can provide data basefor the new sintering method and heat storage model.