Effect of Aluminum Content on Wear Resistance of Hot-Forged Multiphase Steel
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RODUCTION
THE morphology of the bainite phase highly depends on the transformation temperature and chemistry. Lower bainite (LB) is obtained at a low temperature providing a higher dislocation density matrix and a very fine microstructure,[1] which results in a good combination of mechanical properties.[2,3] On the other hand, the upper bainite (UB) is obtained at a high-temperature range producing low mechanical properties.[3,4] Carbide is the main element in the traditional bainite microstructure, and bainite types mainly depend on the distribution of carbide. For UB, carbide is distributed on the lath boundaries, whereas LB is characterized by the precipitation of carbide within the bainitic ferrite plate.[5–9] A carbide-free bainite microstructure is characterized by high strength and toughness.[10,11] Nowadays, carbide-free bainite steels are widely manufactured and used in many industries, such as automotive,
bearing, gear, and railway systems (including rails and crossings).[12–14] Wang et al. and Qian et al. found that the medium- or low-carbon steel of a bainite microstructure after a heat treatment process in a low-temperature range had an optimum microstructure and mechanical properties.[15,16] The overall study about obtaining carbide-free UB and LB morphologies in a medium-carbon steel has not yet been reported in the literature. Therefore, in this study, medium-carbon steel was alloyed with Mn, Cr, Si, and Al to obtain carbide-free bainite. Different bainite ferrite and retained austenite morphologies and their mechanical performances were characterized and analyzed by using optical and scanning electron microscopes (OM and SEM, respectively). The wear resistance and worn surface of these steels were investigated.
II.
EXPERIMENTAL WORK
A. Material Preparation
MASOUD IBRAHIM MOHAMED, Associate Professor, is with the Department of Chemical and Materials Engineering, Faculty of Engineering, Northern Border University, Arar, Postal Code 1321, Kingdom of Saudi Arabia, and is on leave from the Industrial Engineering Department, Faculty of Engineering, Fayoum University, Fayoum, Egypt. Contact e-mail: [email protected] AHMED ISMAIL ZAKY FARAHAT, Associate Professor, is with the Plastic Deformation Department, Central Metallurgical Research and Development Institute, P.O.Box 87, Helwan, Cairo, Egypt. J.A. AL-JARRAH, Associate Professor, is with the Department of Mechanical Engineering, Faculty of Engineering, Northern Border University, Arar, Postal Code 1321, Kingdom of Saudi Arabia. Manuscript submitted October 29, 2015. Article published online October 26, 2016 314—VOLUME 48A, JANUARY 2017
A casting of a 100 kg of steel with different alloying elements in an open-air induction furnace was carried out. The yield metal was made in Y-block shapes of 40 mm thickness. The chemical composition is listed in Table I. Machining and cutting operations for the hot-forging process were carried out. The dilatation curve was measured to detect the different transformation temperatures, such as AC1, AC3, Bs, Bf, and
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