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Compound Boronizing and Its Kinetics Analysis for H13 Steel with Rare Earth CeO2 and Cr2O3

The compound boronizing of H13 steel sample was carried out by adding rare earth CeO2, and the effects of main parameters of compound boronizing on the properties of the boronizing layer were investigated. The boronizing kinetics were also analyzed. Under the conditions of boronizing temperatures of 850 °C, 900 °C, 950 °C, and 1000 °C, and boronizing times of 2 h, 3 h, 4 h, and 5 h, the boronizing experiment was carried out by adding CeO2 with mass fraction of 2%, 4% and 6%, Cr2O3 with a mass fraction of 1%, 2%, 3%, and 4%. The results show that boronizing H13 steel with rare earth CeO2 is conducive to the diffusion of boron atoms and can significantly improve the thickness and microhardness of boronizing layer. Boronizing kinetic analysis shows that the diffusion activation energy of boron atom decreases significantly when the rare earth content is 4%, which indicates that the content of rare earth CeO2 with 4% is an ideal selection for considering improving the utilization rate of rare earth materials, and the boronizing kinetic analysis can provide a quantitative basis for determining the content of rare earth metals. Therefore, experiments and analysis show that for H13 steel, when the boronizing temperature is 950 °C, time is 4 h and rare earth content is 4%, the thickness of the boronizing layer can reach 71 μm and the microhardness at the depth of 70 μm from the surface layer can reach 1546.32 HV. Moreover, on this basis, when Cr2O3 with a rare earth content of 2% is added, the microstructure and wear resistance of the boronizing layer are significantly improved.