Ağır Araç Fren Balatalarında Katı Yağlayıcıların Deney Tasarımı Tabanlı İncelenmesi

Abstract

Ağır hizmet araçları için fren balatası formülasyonlarının, aşırı frenleme koşulları altında aşınma direnci, fade direnci ve sürtünme kararlılığı arasında bir denge sağlaması gerekmektedir. Bu çalışma, grafit, antimon trisülfür (Sb₂S₃), molibden disülfür (MoS₂), çinko sülfür (ZnS) ve kalsiyum florür (CaF₂) içeren katı yağlayıcı bileşimlerinin bakır içermeyen fren balatalarının tribolojik performansı üzerindeki etkisini sistematik olarak incelemektedir. Çalışmada, bu yağlayıcıların sürtünme katsayısı, aşınma oranı ve fade direnci üzerindeki etkisini değerlendirmek için Deney Tasarımı (DOE) yöntemi uygulanmış ve testler ECE R90 koşulları altında Krauss tipi sürtünme test cihazı kullanılarak gerçekleştirilmiştir.Elde edilen bulgular, CaF₂’nin sürtünme katsayısını önemli ölçüde artırdığını, Sb₂S₃’ün fade direncini iyileştirdiğini ancak aşınma oranını da artırdığını göstermektedir. Grafitin ise fade direnci veya sürtünme kararlılığı üzerinde belirgin bir etkisi olmadan aşınma kaybını azalttığı belirlenmiştir. Genel Faktöriyel Regresyon ve Varyans Analizi (ANOVA) sonuçları, MoS₂ ve Sb₂S₃’ün fade direnci üzerinde en etkili faktörler olduğunu, grafitin ise aşınma kaybını azaltmada baskın rol oynadığını ortaya koymuştur. Bu çalışma, ağır hizmet uygulamaları için üstün frenleme performansı sağlamak amacıyla optimize edilmiş çok bileşenli metal sülfür formülasyonlarının gerekliliğini vurgulamaktadır. Özellikle MoS₂ ve Sb₂S₃ içeren sinerjik yağlayıcı kombinasyonlarının tribofilm kararlılığını artırarak fren balatalarının dayanıklılığını iyileştirdiği gösterilmiştir. Gelecekteki araştırmalar, bu bileşimlerin daha da optimize edilmesine ve gerçek dünya frenleme koşulları altında uzun vadeli performanslarının detaylı olarak incelenmesine odaklanmalıdır.

Keywords

• Fren balataları
• katı yağlayıcılar
• triboloji
• sürtünme
• ANOVA

A Design of Experiments-Based Investigation of Solid Lubricants in Heavy Vehicle Brake Pads

Abstract

Brake pad formulations for heavy-duty vehicles must balance wear resistance, fade resistance, and friction stability under extreme braking conditions. This study systematically investigates the impact of solid lubricant compositions, including graphite, antimony trisulfide (Sb₂S₃), molybdenum disulfide (MoS₂), zinc sulfide (ZnS), and calcium fluoride (CaF₂), on the tribological performance of copper-free brake pads. A Design of Experiments (DOE) approach was employed to develop 29 unique formulations and evaluate them under the ECE R90 test procedure using a Krauss friction tester. Statistical analyses were used to determine the effects of lubricant combinations on performance metrics. The findings revealed that increasing CaF₂ content led to a significant rise in the coefficient of friction (up to 0.46), whereas Sb₂S₃ enhanced fade resistance by reducing loss of friction coefficient to as low as 0.03 but increased wear. MoS₂ was associated with superior thermal stability, while graphite primarily contributed to reduced wear loss (minimum 0.009 g). The formulation containing 10 wt% graphite, 2.5 wt% MoS₂, and 2.5 wt% CaF₂ demonstrated the most optimal balance of performance. These results underscore the importance of synergistic solid lubricant combinations in improving the durability and effectiveness of environmentally friendly brake pad formulations for heavy-duty applications.

Keywords

• Brake pads
• solid lubricants
• tribology
• friction
• ANOVA

References

1. Singh, S., Kalel, N., Darpe, A., et al. (2020). Controlling the performance of copper-free brake-pads by varying size of graphite particles. In SAE Technical Papers. SAE International.
2. Kijanski, J., Otto, J., Stebner, F., et al. (2020). Investigation of influences on brake pad wear. In SAE Technical Papers. SAE International.
3. Druzhinina, M., & Stefanopoulou, A. G. (2002). Speed control experiments for commercial heavy vehicles with coordinated friction and engine compression brakes. In Proceedings of the American Control Conference. IEEE Xplore.
4. Antonyraj, I. J., & Singaravelu, D. L. (2019). Tribological characterization of various solid lubricants based copper-free brake friction materials: A comprehensive study. In Materials Today: Proceedings (pp. 2650–2656). Elsevier.
5. Le Gigan, G., Vernersson, T., Lundén, R., & Skoglund, P. (2015). Disc brakes for heavy vehicles: An experimental study of temperatures and cracks. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 229(5), 684–707. SAGE Publications.
6. Martinez, A. M., & Echeberria, J. (2016). Towards a better understanding of the reaction between metal powders and the solid lubricant Sb2S3 in a low-metallic brake pad at high temperature. Wear, 348–349, 27–42. https://doi.org/10.1016/j.wear.2015.11.014
7. Kalel, N., Bhatt, B., Darpe, A., & Bijwe, J. (2020). Eco-friendly brake-pads using ferritic stainless-steel particles of varying sizes: Influence on performance properties. In SAE Technical Papers. SAE International.
8. Justin Antonyraj, I., Vijay, R., & Lenin Singaravelu, D. (2019). Influence of WS2/SnS2 on the tribological performance of copper-free brake pads. Industrial Lubrication and Tribology, 71(3), 398–405. https://doi.org/10.1108/ILT-06-2018-0249

9. Österle, W., & Dmitriev, A. (2016). The role of solid lubricants for brake friction materials. Lubricants, 4(1), 5. https://doi.org/10.3390/lubricants4010005
10. Melcher, B., & Faullant, P. (2000). A comprehensive study of chemical and physical properties of metal sulfides. In SAE Technical Papers. SAE International.
11. Ertan, R., & Yavuz, N. (2011). The effects of graphite, coke and ZnS on the tribological and surface characteristics of automotive brake friction materials. Industrial Lubrication and Tribology, 63(4), 245–253. https://doi.org/10.1108/00368791111140468
12. Barros, L. Y., Poletto, J. C., Gehlen, G. S., et al. (2023). Transition in wear regime during braking applications: An analysis of the debris and surfaces of the brake pad and disc. Tribology International, 189, 108968. https://doi.org/10.1016/j.triboint.2023.108968
13. Sathickbasha, K., Selvakumar, A. S., Balaji, M. A. S., & Rajan, B. S. (2019). The dual role of metal sulfides as lubricant and abrasive: An interface study in friction composite. Materials Research Express, 6(1). https://doi.org/10.1088/2053-1591/aafd5a
14. Balaji, P., Sathickbasha, K., & Baskara Sethupathi, P. (2024). The significance of low and high temperature solid lubricants for brake friction applications and their tribological investigation. Tribology International, 191, 109109. https://doi.org/10.1016/j.triboint.2023.109109
15. Ouyang, J.-H., Li, Y.-F., Zhang, Y.-Z., et al. (2022). High-temperature solid lubricants and self-lubricating composites: A critical review. Lubricants, 10(8), 177. https://doi.org/10.3390/lubricants10080177
16. Zhang, P., Zhang, L., Wei, D., et al. (2019). Effect of graphite type on the contact plateaus and friction properties of copper-based friction material for high-speed railway train. Wear, 432–433. https://doi.org/10.1016/j.wear.2019.202927
17. Cho, M. H., Ju, J., Kim, S. J., & Jang, H. (2006). Tribological properties of solid lubricants (graphite, Sb2S3, MoS2) for automotive brake friction materials. Wear, 260(7–8), 855–860. https://doi.org/10.1016/j.wear.2005.04.003
18. Vijay, R., Singaravelu, L. D., & Filip, P. (2020). Influence of molybdenum disulfide particle size on friction and wear characteristics of non-asbestos-based copper-free brake friction composites. Surface Review and Letters, 27(9), 1950085. https://doi.org/10.1142/S0218625X19500859
19. Vijay, R., Manoharan, S., Nagarajan, S., & Singaravelu, L. D. (2021). Influence of premixed dual metal sulfides on the tribological performance of copper-free brake friction materials. Industrial Lubrication and Tribology, 73(2), 266–274. https://doi.org/10.1108/ILT-03-2020-0116
20. Makhesana, M. A., & Patel, K. M. (2021). Improvement in friction and wear characteristics using CaF2 as a solid lubricant at different conditions. Metal Powder Report, 76(S1), S55–S65. https://doi.org/10.1016/j.mprp.2020.06.058
21. Washington State Department of Ecology. (n.d.). Better Brakes Law. Retrieved May 9, 2025, from https://ecology.wa.gov/waste-toxics/reducing-toxic-chemicals/washingtons-toxics-in-products-laws/better-brakes-law
22. Bilvatej, B., Naveen, J., Karthikeyan, N., et al. (2024). Progress in polymeric and metallic brake pads: A comprehensive review. Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 238(1), 3–25. https://doi.org/10.1177/13506501231204655
23. European Agency for Safety and Health at Work. (2006). Regulation (EC) No 1907/2006 - Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH). Retrieved May 8, 2025, from https://osha.europa.eu/en/legislation/directives/regulation-ec-no-1907-2006-of-the-european-parliament-and-of-the-council
24. United Nations Economic Commission for Europe (UNECE). (2012). ECE R90: Uniform provisions concerning the approval of replacement brake lining assemblies, drum brake linings and discs and drums for power-driven vehicles and their trailers.
25. Lin, H. Y., Cheng, H. Z., Lee, K. J., et al. (2020). Effect of carbonaceous components on tribological properties of copper-free NAO friction material. Materials, 13(5), 1163. https://doi.org/10.3390/ma13051163
26. Lee, W. K., Rhee, T. H., Kim, H. S., & Jang, H. (2013). Effects of antimony trisulfide (Sb2S3) on sliding friction of automotive brake friction materials. Metals and Materials International, 19(6), 1101–1107. https://doi.org/10.1007/s12540-013-5027-x