ORIGINAL ARTICLE Microstructures, hardening and tribological behaviors of tin matrix composites reinforced with SiC and Zn particles Fatemeh Ghasemi, Mohammad Moazami-Goudarzi* , Hamidreza Najafi Received: 29 September 2019 / Revised: 1 December 2019 / Accepted: 9 July 2020 Ó The Nonferrous Metals Society of China and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Abstract In order to strengthen pure tin and improve its dry sliding resistance, Sn/SiC and Sn/Zn composites were fab- ricated via a powder metallurgy route. Microstructure, hardness and pin-on-disk wear resistance of pure tin and the fabricated composites were compared to those of Sn–7.5Sb– 3.5Cu Babbitt alloy. The dominant wear mechanism at dif- ferent applied loads was determined by analyzing worn surfaces and wear debris in each case. The results showed that the hardening effect of Zn was much higher than that of SiC. The hardening role of Zn in the tin matrix was ascribed to the direct load transfer mechanism. Microscopic studies of the worn surfaces revealed that the pure tin was susceptible to surface fatigue wear and plowing damage, depending on the normal load applied during the wear test. In the case of Sn/ SiC composite and the Babbitt alloy, delamination wear mechanism resulting from subsurface crack propagation controlled the wear rate. While the highest hardness and the lowest coefficient of friction were obtained for the Babbitt alloy, the Sn/Zn composite exhibited the highest wear resistance at a constant applied load, indicating the impor- tance of asperity contact type in the wear process. Keywords Tin matrix composites; Babbitt alloy; Microstructure; Hardening mechanisms; Wear behavior 1 Introduction Sliding bearings are critical machine elements widely employed in petrol and diesel engines, centrifugal pumps and steam and gas turbines [1, 2]. Some sliding bearings operate in conditions where a direct contact between the asperities of the two surfaces is inevitable. Therefore, proper material selection is required to minimize the wear damage. Besides, an appropriate combination of compati- bility, conformability, embeddability, fatigue strength and corrosion resistance is required for sliding bearings to be able to function successfully [3]. Accordingly, bearing materials should have well-adjusted mechanical properties which can only be achieved by unique microstructures observed in certain special alloys. In this regard, bearing metals are usually multi-phase alloys comprised of both soft and hard microstructural constituents [4]. Tin is well recognized as an excellent bearing material. In this regard, tin-based Babbitt alloys (or white metals) are probably the best known and most commonly used bearing materials usually containing * 3.0 wt%–8.5 wt% copper and more than 4.0 wt% antimony [5]. Babbitt alloys are typically generated through melt processing techniques, and their bearing performance is guaranteed by the for- mation of hard Cu 6 Sn 5 and SbSn precipitates within a soft matrix of tin-rich solid solution during solidification [6]. However, the strength of these alloys may not be suit- able for certain applications. Many authors have recently attempted to improve the mechanical properties and wear resistance of Babbitt alloys in order to expand their working conditions. For instance, Dong et al. [7] reported that both tensile strength and ductility of Sn–11Sb–6Cu Babbitt alloy were increased by the addition of 1 wt% Ag. Zhang et al. [8] improved the tribological performance of Sn–10.5Sb–7Cu Babbitt alloy by fabricating a multi-layer surface texture consisting of the main grooves and sec- ondary micro-dimples on the Babbitt substrate. The increased hardness and reduced wear rate of Sn–11Sb–6Cu Babbitt alloy through the modification of microstructure by F. Ghasemi, M. Moazami-Goudarzi*, H. Najafi Department of Materials Engineering, Science and Research Branch, Islamic Azad University, Tehran 1477893855, Iran e-mail: moazami@srbiau.ac.ir 123 Rare Met. https://doi.org/10.1007/s12598-020-01535-w RARE METALS