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High temperature tribological behaviors of plasma electrolytic borocarburized Q235 low-carbon steel

2013; Elsevier BV; Volume: 232; Linguagem: Inglês

10.1016/j.surfcoat.2013.04.064

1879-3347

Bin Wang, Xiaoyue Jin, Wenbin Xue, Zhenglong Wu, Jiancheng Du, Jie Wu,

Metal and Thin Film Mechanics

Abstract Plasma electrolytic boronizing is a novel technique to fabricate rapidly a hardening layer on steel. In this study, a boride layer on Q235 low-carbon steel was prepared by plasma electrolytic borocarburizing process (PEB/C) in the 30% borax electrolyte with carbon-containing organic additive at 330 V. The microstructure and phase constituent of the PEB/C steel were analyzed by SEM and XRD. Microhardness profile of the PEB/C steel was determined, and its tribological properties under dry sliding against ZrO 2 ceramic ball were evaluated using a ball-on-disk friction tester at ambient temperature and high-temperature (up to 500 °C) environments. Friction coefficient and wear rate before and after PEB/C treatment were measured, and the wear mechanism was also discussed. The results show that the boride layer mainly consists of the Fe 2 B phase, the hardness of which is close to 1800 HV. The PEB/C treatment could significantly decrease the friction coefficient and improve wear resistance of the low-carbon steel. Meanwhile, the friction coefficient and wear rate of the untreated and PEB/C treated steel samples also increase with increasing the environment temperature, but the wear rate of PEB/C treated steel is always much lower than that of the untreated steel at different environment temperatures. Plasma electrolytic borocarburized low-carbon steel can maintain higher wear resistance at high temperature environment, which ascribes to the formation of Fe 2 B phase with good thermal stability in the hardening layer. The wear mechanism of untreated low-carbon steel is mainly the fatigue wear at ambient temperature and the fatigue wear and adhesive wear at 200 °C. The PEB/C treated steel displays the adhesive wear at 200 °C. However both the untreated and PEB/C treated samples are transferred to the oxidation wear and adhesive wear at 500 °C.