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In this article, the effect of Ce element on the microstructure and mechanical properties was studied by Ce addition to the hot‐formed steel. Scanning electron microscope and energy dispersive spectrometer (SEM‐EDS) was used to analyze the improvement effect of Ce on inclusions and the effect of inclusions on fracture behavior; Electron back scattering diffractometer (EBSD) was used to analyze the refinement and strengthening effect of Ce on martensitic grains; transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM) was used to analyze the microstructure strengthening effect and microalloying effect of solid solution Ce in hot‐formed steel. Through a systematic analysis of mechanical properties and microstructure, the mechanism of Ce enhances the strength and elongation of hot‐formed steel was clarified. Besides, this work provides a research basis for further improving the safety and machinability of hot‐formed steel. [ABSTRACT FROM AUTHOR]

In this paper, the effect of Ce addition on high temperature oxidation behavior of hot-formed steel was studied by high temperature oxidation experiment. The structure and phase composition of surface oxide layer of specimens with different Ce content were systematically analyzed by SEM, EDS, XPS. The results showed that the addition of Ce promoted the formation of a dense oxide layer during the initial oxidation stage, and effectively weaken the oxidation degree of the steel surface. Meanwhile, the Ce2O3 particles segregation in Si–Cr rich phase reduced the concentration of vacancy defects in oxide layer and enhanced the adhesion between oxide layer and substrate. After Ce addition, the surface oxidation resistance of hot-formed steel is significantly improved.

In this study, the effect of passive film on the high-temperature oxidation process of a PHS1500 hot-formed steel was investigated through molybdate passivation and austenitizing high-temperature oxidation experiments. The corrosion resistance and phase composition of the passive film were tested by electrochemical impedance test and X-ray photoelectron spectroscopy. The structure and phase composition of the oxide layer were also systematically analyzed. The passive film affects the oxide layer structure of hot-formed steel through the influence of the Si-rich phase formation. After the molybdate passivation treatment, the oxidation resistance of hot-formed steel significantly improved. • Passivation and high-temperature oxidation of PHS1500 hot-formed steel was studied. • Na 2 MoO 4 solution was used for the passivation of the hot-formed steel. • Si-rich phase formation of the passive film affects the oxide layer structure. • Oxidation resistance significantly improved after the molybdate passivation treatment. [ABSTRACT FROM AUTHOR]

A method for plotting thermokinetic and isothermal diagrams of decomposition of supercooled austenite in powder porous steels with the help of a high-accuracy magnetometer is suggested. Thermokinetic and isothermal diagrams of decomposition of supercooled austenite in hot-formed powder steel PK40N2M are analyzed. [ABSTRACT FROM AUTHOR]