The phase stability and mechanical properties of boron carbides in Fe–Cr–B boron-bearing high-speed steel were determined via the first-principles calculation method of the density functional theory. The types of boron carbides in this steel were determined through equilibrium thermodynamic phase diagrams and X-ray diffraction analysis of the material. In addition, the lattice constant, binding energy, electronic density of states, mechanical properties, and hardness of boron carbides were calculated with the VASP software. The results showed that VC, WC, Fe₂B, Mo₂B, W₂B, and W₂FeB₂ were stable in Fe–Cr–B boron-bearing high-speed steel. Among these compounds, VC exhibited the highest thermodynamic stability (enthalpy of formation: –44.16 kJ mol^–1). The boron carbides all exhibited metallic characteristics. Furthermore, the corresponding electronic density of states was contributed mainly by the P orbit of B and C atoms and the d orbit of Fe, Mo, V, and W. Except for the ratio of WC, the B_H /G_H ratios of all phases were >1.75, indicating that these phases were all ductile. Poisson's ratios of ∼0.25 were obtained, consistent with the ionic-covalent nature of the compounds. When the B measurement ratio increased, the hardness of the phases with rich B surpassed the hardness of the phases with rich C. The highest Debye temperature (906.65 K) was obtained for VC, which had the strongest covalent bond, as evidenced by the width of its pseudogap.

Purpose: The purpose of this paper is to study the microstructure and the high-temperature tribology behavior of a high-speed steel (HSS) roller material with boron as the main alloy element under different heat treatments, aiming to provide some theoretical references for its engineering application. Design/methodology/approach: The samples of high boron HSS were quenched at 900°C, 1,000°C, 1,050°C and 1,150°C. The microstructure, composition and phase composition of this new HSS were analyzed by OM, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffractometer. The surface hardness and the tribology behavior under high temperature were measured by Rockwell hardness tester and the high-temperature friction and wear tester. The wear morphology was observed by SEM. Findings: The high-temperature friction coefficient and the relative wear rate of the high boron HSS decrease first, then increase with the rise of the quenching temperature. When the quenching temperature is 1,050°C, both the friction coefficient (0.425) and the relative wear rate (79 per cent) are the smallest. Under the high-temperature friction environment, the high boron HSS mainly includes oxidation wear, adhesive wear and abrasive wear. The effect of abrasive wear is weakened gradually with the rise of the quenching temperature, and the high-temperature wear resistance is improved significantly. Compared with the traditional roll materials, the service life of the new high boron HSS is greatly improved. It is an ideal substitute product for the high chromium cast iron roll. Originality/value: The boron element replaces other precious metals in high boron HSS, which has the advantage of low production cost, and it has a wide application in the field of roll materials. In this paper, the microstructure, the transformation of hard phases and the high-temperature tribology behavior of this new high boron HSS under different heat treatments were studied, aiming to provide some theoretical references for its engineering application.