Wear Behavior and Mechanism of a Cr-Mo-V Cast Hot-Working Die Steel
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-WORKING dies, as tools used for the hot shaping of metal, play an important role in many industries, such as automobile, autocycle, agricultural machinery, etc. AISI H11, H13, H20, H21, and H22 are commonly used hot-working die steels.[1,2] Cast hotworking steels have been studied and used increasingly as an alternative for traditional hot-working dies since the 1940s, because of their advantages such as high use ratio of materials, low finish allowance, short process time, and the recyclability of obsolete dies.[3–6] Hot-working dies are subjected to high mechanical and thermal loadings, with the wear being the most important cause of failure.[7–10] Therefore, increased wear resistance is an important reason for the development of a new Cr-Mo-V cast hot-working die steel.[11–13] Wang et al. and Cui et al. studied the effects of alloying elements,[14,15] rare-earth modification,[16] and second carbides[17,18] on the elevated-temperature wear of this cast steel. Wei et al.[19] studied the wear behavior of the cast steel at 673 K (400 °C) and discovered that the cast steel had a substantially higher wear resistance than H13 and H21 steels. No systematic investigation of the wear M.X. WEI, Ph.D. Student, S.Q. WANG, Professor, Y.T. ZHAO, Professor, K.M. CHEN, Associate Professor, and X.H. CUI, Associate Professor, are with the School of Materials Science & Engineering, Jiangsu University, Zhenjiang 212013, P.R. China. Contact e-mails: [email protected]; [email protected] Manuscript submitted March 24, 2010. Article published online November 23, 2010 1646—VOLUME 42A, JUNE 2011
of the newly developed Cr-Mo-V cast steel has been reported,[13–19] and the wear behavior and wear mechanism are addressed in the current study.
II.
EXPERIMENTAL DETAILS
The cast hot-working die steel (0.35C-3Cr-2Mo-1V) was melted in a 50 kg medium frequency induction furnace with a nonoxidation method. At 1823 K (1550 °C), the melt was deoxidized by aluminum and then poured. The modified agents containing the rare metal elements (RE) were put in a ladle for the modification of the melt. Finally, the standard wedgeshaped specimen was cast. The cast steel was austenitized at 1293 K (1020 °C) for 30 minutes, quenched in oil to attain martensite with a hardness of 53 HRC, and subsequently tempered at 473 K, 823 K, and 973 K (200 °C, 550 °C, and 700 °C) for 2 hours to produce tempered martensite (Tm), tempered troostite (Tt), and tempered sorbide (Ts), respectively, with the respective hardnesses of 51, 50, and 30 HRC. The pin specimens were of 6 mm diameter and 12 mm length; the disks were of 70 mm diameter and 8 mm thickness. The cast steel was used for the pin specimens, whereas the disk specimens were made of a commercial D2 steel with a heat-treated hardness of 60 HRC. Prior to each test, the contact surfaces of the pin and disk specimens were prepared by grinding against a 400-grit silicon carbide paper to attain an Ra value of about 0.45 lm then cleansed with alcohol. METALLURGICAL AND MATERIALS TRANSACTIONS A
Dry-sliding wear tests were co
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