Production of Spherical Cementite within Bainitic Matrix Microstructures in High Carbon Powder Metallurgy Steels
The hardness-microstructure relationships of spherical cementite in bainitic matrix obtained by a different heat treatment cycles carried out to high carbon powder metallurgy (P/M) steel were investigated. For this purpose, 1.5 wt.% natural graphite powder admixed in atomized iron powders and the mixed powders were compacted under 700 MPa at room temperature and then sintered at 1150 °C under a protective argon gas atmosphere. The densities of the green and sintered samples were measured via the Archimedes method. A density of 7.4 g/cm3 was obtained after sintering and a density of 94% was achieved. The sintered specimens having primary cementite plus lamellar pearlitic structures were fully quenched from 950 °C temperature and then over-tempered at 705 °C temperature for 60 minutes to produce spherical-fine cementite particles in the ferritic matrix. After by this treatment, these samples annealed at 735 °C temperature for 3 minutes were austempered at 300 °C salt bath for a period of 1 to 5 hours. As a result of this process, it could be able to produced spherical cementite particle in the bainitic matrix. This microstructure was designed to improve wear and toughness of P/M steels. The microstructures were characterized and analyzed by SEM and micro and macro hardness.
Digital Object Identifier (DOI): doi.org/10.5281/zenodo.2643577Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 345
 Ashrafizadeh F., Influence of plasma and gas nitriding on fatigue resistance of plain carbon (Ck45) steel, Surf. Coat. Technol. 174, 1196.1200, (2003).
 Wu, M., Tsao, L., Shu, G., Lin, B.: Mater. Sci. Eng. A, 538, 2012, p. 135. Doi :10.1016/j. Msea. 2011.12.113.
 Wu, M. W., Tsao, L. C., Chang, S. Y.: Mater. Sci. Eng. A, 565, 2013, p. 196. doi:10.1016/j.msea.2012.12.032.
 S. Tekeli, A. Güral. Dry sliding wear behaviour of heat treated iron based powder metallurgy steels with 0.3% Graphite + 2% Ni additions. Materials and Design 28 (2007) 1923–1927.
 Altuntaş, O.: Investigation of Spheroidization Heat Treatment Effects on Microstructure and Impact Toughness Properties of High Carbon Powder Metal Steels. (Master Thesis). Ankara, Gazi University Institute of Science and Technology 2013.
 Wang, B., Liu, Z. Y., Zhou, X. G., Wang, G. D.: Journal of Iron and Steel Research, 20, 2013, p. 25. doi:10.1016/S1006-706X(13)60107-7.
 Wu, T., Wang, M. Z., Gao, Y. W., Li, X. P., Zhao, Y. C., Zou, Q.: Journal of Iron and Steel Research, 19, 2012, p. 60. doi:10.1016/S1006-706X(12)60140-X.
 Lv, Z. Q., Wanga, B., Wang, Z. H., Sun, S. H., Fu, W. T.: Mater. Sci. Eng. A, 574, 2013, p. 143. doi:10.1016/j.msea.2013.02.059.
 Yi, H. L., Hou, Z. Y., Xu, Y. B., Wu, D., Wang, G. D.: Scripta Materialia, 67, 2012, p. 645. doi:10.1016/j.scriptamat.2012.07.020.
 Krauss, G. Steels: Processing, Structure, and Performance, ASM International, (2005).
 H. Bhadeshia, New bainitic steels by design, Displac. Phase Transform. Appl. Mater. Eng. (1998)69–78.
 C. Pitt, Wear and microstructure relationships in carbide-free bainitic rail steels, (Ph. D. thesis), University of Cambridge, 1999.
 X. Feng, F. Zhang, J. Kang, Sliding wear and low cycle fatigue properties of new carbide free bainitic rail steel, Mater. Sci. Technol. 30 (12) (2014) 1410–1418, http://dx.doi.org/10.1179/1743284713Y.0000000474.
 S. Bakshi, P. Shipway, H. Bhadeshia, Three-body abrasive wear of fine pearlite, nanostructured bainite and martensite, Wear 308 (2013) 46–53, http://dx.doi.org/10.1179 / 1743284713Y.0000000474.
 M. Zhang, H. Gu, Fracture toughness of nanostructured railway wheels, Eng. Fract. Mech.75 (18) (2008) 5113–5121, http://dx.doi.org/10.1016/j. engfracmech.2008.07.007.
 M. Sherif, P. Rivera-Diaz-del Castillo, H. Bhadeshia, H. Huang, S teel alloy WO 2013149657 A1, 2013.
 P. Rivera-Diaz-delCastillo, B. Szost, R. Vegter, H. Bhadeshia, Bearing steel WO 2014121836 A1,2014.
 C. Garcia-Mateo, F. Caballero, Advanced high strength bainitic steels, Compr. Mater. Process.1 (2014)165–190.
 Tu, Meng-Yin, et al. "Comparison of microstructure and mechanical behavior of lower bainite and tempered martensite in JIS SK5 steel." Materials Chemistry and Physics 107.2-3 (2008): 418-425.
 Sawa M, Rigney DA. Sliding behavior of dual-phase steels in vacuum and air. Wear 1987;119:369–90.