Dry sliding friction and wear in plain carbon dual phase steel
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L phase (DP) steel consists of hard martensite islands embedded in a relatively soft and ductile ferrite matrix.[1] It has the potential to be used as a wear resistant material. In the field of mineral processing, mining and pipeline transportation of slurry, DP steel has already been employed.[2] The tribology of dual phase steels has not yet been explored extensively, and only a few studies have been reported.[3,4] Wayne and Rice[3] have shown the dependence of wear on microstructure and have concluded that the duplex microstructure of DP steel offers higher wear resistance than that observed in a steel with spheroidal carbides. The wear resistance of DP steel depends on the volume fraction of martensite.[3] Sawa and Rigney[4] have found that the wear behavior of DP steel also depends strongly on its morphology, i.e., the shape, size, and distribution of its martensite. They have also observed a transition in the friction coefficient with sliding distance, accompanied by a sudden increase in wear.[4] The work reported is part of a detailed study on the comparative wear and friction characteristics of plain carbon DP and normalized (N) steels, using a standard pin-on-disk wear testing machine. II. EXPERIMENTAL PROCEDURE Cylindrical pin samples (30 mm ⫻ 6.25 mm ) of commercial grade 0.14 pct C steel (Table I) were used for the RAJNESH TYAGI, Research Scholar, S.K. NATH, Associate Professor, and S. RAY, Professor, are with the Department of Metallurgy and Materials Engineering, University of Roorkee, Roorkee - 247667, India. Manuscript submitted December 7, 1999. METALLURGICAL AND MATERIALS TRANSACTIONS A
current investigation. All the samples were normalized at 950 ⬚C for 15 minutes. A number of these samples were intercritically annealed to develop the desired dual phase structure of martensite and ferrite. Intercritical annealing was conducted in a vertical tube furnace at 740 ⬚C for 5 minutes, followed by water quenching; the details have been described earlier.[5] Intercritical annealing for 5 minutes is not long enough to attain equilibrium, and annealing time in this range could be used as a variable to control the amount of phases.[6] Metallographic structures were analyzed to determine the volume fractions of both martensite in the DP steel and pearlite in the N steel, using the pointcounting method.[7] The macrohardness and microhardness of these samples were measured at loads of 30 and 0.01 kg, respectively, using calibrated standard hardness-testing machines. Wear tests were conducted using pin samples that had flat surfaces in the contact region and in the rounded corner, and that were polished up to 4/0 grade (⬃ 38 m) of emery paper and cleaned with acetone to remove dust and grease from the surface of the pin. The tests were done at a relative humidity of 55 to 75 pct at room temperature (25 ⬚C). Dry sliding was carried out against the counterface of a hardened and polished disk made of En-32 steel that had a HRC 62 to 65 hardness. A sturdy pin-on-disk machine was used as shown schematically in Figur
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