Solid FeS lubricant: a possible alternative to MoS₂ for Cu–Fe-based friction materials

Abstract

Molybdenum disulfide (MoS₂) is one of the most commonly used solid lubricants for Cu–Fe-based friction materials. Nevertheless, MoS₂ reacts with metal matrices to produce metal sulfides (e.g., FeS) and Mo during sintering, and the lubricity of the composite may be related to the generation of FeS. Herein, the use of FeS as an alternative to MoS₂ for producing Cu–Fe-based friction materials was investigated. According to the reaction principle of thermodynamics, two composites—one with MoS₂ (Fe–Cu–MoS₂ sample) and the other with FeS (FeS–Cu₂S–Cu–Fe–Mo sample), were prepared and their friction behaviors and mechanical properties were compared. The results showed that MoS2 reacted with the Cu–Fe matrix to produce FeS, metallic ternary sulfides, and Mo when sintered at 1050°C. The MoS₂–Cu–Fe and FeS–Cu₂S–Cu–Fe–Mo samples thereby exhibited similar characteristics with respect to phase composition, density, hardness, and tribological behaviors. Micrographs of the worn surfaces revealed that the stable friction regime for both composites stemmed from the iron sulfides friction layers rather than from the molybdenum sulfides layers.

Keywords

friction materials / solid lubricants / iron sulfides / molybdenum sulfides

References

[1] German R.M. Powder Metallurgy and Particulate Materials Processing: The Processes, Materials, Products, Properties, and Applications, 2005, Princeton, Metal Powder Industries Federation.

[2] Zhang G.M., Feng K.Q., Li Y., Yue H.F. Effects of sintering process on preparing iron-based friction material directly from vanadium-bearing titanomagnetite concentrates. Mater. Des., 2015, 86, 616.

[3] Ram Prabhu T., Varma V.K., Vedantam S. Effect of reinforcement type, size, and volume fraction on the tribological behavior of Fe matrix composites at high sliding speed conditions. Wear, 2014, 309(1-2): 247.

[4] Österle W., Prietzel C., Kloß H., Dmitriev A.I. On the role of copper in brake friction materials. Tribol. Int., 2010, 43(12): 2317.

[5] Zhao X., Guo L.C., Zhang L., Jia T.T., Chen C.G., Hao J.J., Shao H.P., Guo Z.M., Luo J., Sun J.B. Influence of nano-Al₂O₃-reinforced oxide-dispersion-strengthened Cu on the mechanical and tribological properties of Cu-based composites. Int. J. Miner. Metall. Mater., 2016, 23(12): 1444.

[6] Savan A., Pflüger E., Voumard P., Schröer A., Simmonds M. Modern solid lubrication: Recent developments and applications of MoS₂. Lubr. Sci., 2000, 12(2): 185.

[7] Erdemir A. Review of engineered tribological interfaces for improved boundary lubrication. Tribol. Int., 2005, 38(3): 249.

[8] Clauss F.J. Solid Lubricants and Self-Lubricating Solids, 2012, Amsterdam, Elsevier 78.

[9] Cho M.H., Ju J., Kim S.J., Jang H. Tribological properties of solid lubricants (graphite, Sb₂S₃, MoS₂) for automotive brake friction materials. Wear, 2006, 260(7-8): 855.

[10] Li S., Feng Y., Ling S., Zhang X.B., Wang J. Effect of sintering temperature on properties of Cu–MoS₂ composite materials. Met. Funct. Mater., 2008, 15(1): 24.

[11] Uzunsoy D., Kelesoglu E., Erarslan Y. Contribution of MoS₂ additives to the microstructure and properties of PM copper based brake material. Mater. Test., 2009, 51(5): 318.

[12] Dhanasekaran S., Gnanamoorthy R. Dry sliding friction and wear characteristics of Fe–C–Cu alloy containing molybdenum di sulphide. Mater. Des., 2007, 28(4): 1135.

[13] Dhanasekaran S., Gnanamoorthy R. Heat generation in Fe–C–Cu–MoS₂-sintered spur gears under unlubricated conditions. Proc. Inst. Mech. Eng. Part J J. Eng. Tribol., 2007, 221(6): 645.

[14] Dhanasekaran S., Gnanamoorthy R. Microstructure, strength and tribological behavior of Fe–C–Cu–Ni sintered steels prepared with MoS₂ addition. J. Mater. Sci., 2007, 42(12): 4659.

[15] Kato H., Takama M., Iwai Y., Washida K., Sasaki Y. Wear and mechanical properties of sintered copper–tin composites containing graphite or molybdenum disulfide. Wear, 2003, 255(1-6): 573.

[16] Senthil K.P., Manisekar K., Subramanian E., Narayanasamy R. Dry sliding friction and wear characteristics of Cu–Sn alloy containing molybdenum disulfide. Tribol. Trans., 2013, 56(5): 857.

[17] Furlan K.P., Binder C., Klein A.N., de Mello J.D.B. Thermal stability of the MoS₂ phase in injection moulded 17–4 PH stainless steel. J. Mater. Res. Technol., 2012, 1(3): 134.

[18] Furlan K.P., de Assunção J.Z., Paz G., Binder C., Klein A.N. Sintering studies and microstructural evolution of Fe–MoS₂ mixtures. Mater. Sci. Forum, 2014, 802, 415.

[19] Furlan K.P., Prates P.B., Andrea dos Santos T., Gouvêa Dias M.V., Ferreira H.T., Rodrigues Neto J.B., Klein A.N. Influence of alloying elements on the sintering thermodynamics, microstructure and properties of Fe–MoS₂ composites. J. Alloys Compd., 2015, 652, 450.

[20] Han J.S., Jia J.H., Lu J.J., Wang J.B. High temperature tribological characteristics of Fe–Mo-based self-lubricating composites. Tribol. Lett., 2009, 34(3): 193.

[21] Peng T., Yan Q.Z., Zhang Y., Shi X.J., Ba M.Y. Low-cost solid FeS lubricant as a possible alternative to MoS2 for producing Fe-based friction materials. Int. J. Miner. Metall. Mater., 2017, 24(1): 115.

[22] Wang Y., Yan Q.Z., Zhang F.F., Ge C.C., Zhang X.L., Zhao H.Q. Sintering behavior of Cr in different atmospheres and its effect on the microstructure and properties of copper-based composite materials. Int. J. Miner. Metall. Mater., 2013, 20(12): 1208.

[23] Subramanlan P.R., Kacprza L., Scott W.W. Binary Alloy Phase Diagrams, American Society for Metals, 1986, OH, Metals Park.

[24] Chen J., Yao P., Xiong X. The behaviors of MoS₂ in the sintering process of Fe-based friction materials. Non Met. Mines, 2003, 26(4): 50.