Taguchi optimization of tribological properties and corrosion behavior of self-lubricating Al–Mg–Si/MoS2 composite processed by powder metallurgyoa mark
Self-lubricating aluminum matrix composites (AMCs) can be used to reduce the wear and coefficient of friction (COF) in automotive engine components in which the use of liquid lubricants is not desirable. High temperatures accelerate the oxidation and thermal degradation of a liquid lubricant. In this study, we used powder metallurgy (PM) technique to prepare self-lubricant (MoS2)-based Al–Mg–Si AMCs, designated as Al–Mg–Si–xMoS2 (x in wt.%; x = 1.5, 2.0, 30, 3.5, and 4.0). The dry sliding wear properties were assessed using a pin-on-disk tribometer at various applied loads (20–50 N) and sliding distances (1000–3000 m), based on the Taguchi model (L9). Furthermore, electrochemical corrosion tests such as open circuit potential (OCP) and potentiodynamic polarization (PDP) were performed in a 3.5 wt% NaCl medium. The morphology of the Al–Mg–Si–xMoS2 composites was observed through scanning electron microscopy and energy dispersive spectroscopy to clarify the particle distribution and chemical composition. The results indicated that the addition of MoS2 to Al–Mg–Si decreased the wear and COF and increased the corrosion resistance, compared with those of the pristine Al–Mg–Si matrix alloy under same operating conditions. As the sliding distance increased to 250 m, the COF fluctuated, but it stabilized as the distance approached 3000 m. The effects of the load and reinforcement concentration were more significant than those of the sliding distance and track diameter, as predicted by the Taguchi model and analysis of variance methods.
Line scan EDS-SEM images were also inspected to further explore the particle-matrix bonding in Al–Mg–Si-xMoS2 AMCs. Fig. 2 shows the results of the point EDS, line EDS as well as areal EDS mapping combined to support the particle-matrix bonding in Al–Mg–Si–3MoS2 AMCs. The various regions of interest for EDS analysis are shown in the yellow square in Fig. 2a. It can be seen that the MoS2 particles are embedded in the Al–Mg–Si matrix, as shown in the SEM images (Fig. 2a–f). Most of the particles are scattered except a few localized clustering. At higher resolution, the particle-matrix bonding was confirmed as shown in Fig. 2g and h. The line scan EDS marked across particles in yellow line is shown for the Al and Mo elemental profiles. A robust particle matrix bonding at the interface is identified (Fig. 2h). The bulk EDS recorded from region 1 (Fig. 2g) was shown in “Spectrum 1’” (Fig. 2h). In addition the corresponding “Spectrum 2′ and 3’” (Fig. 2j and k) refers to the bulk EDS taken from reinforcement particle matrix as well as pristine matrix areas, respectively. The EDS spectrum of the composite shows the presence of Mo, S, Al, and Mg, which indicates the reinforcement of the C4 (3.0 wt%) samples.This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (Nos. 2021R1A2C1005478 and 2021R1A4A1031357). Neeraj Kumar thanks Prof. Manoj Chopkar, Metallurgical and Materials Engineering Dept. and Prof. Ayush Khare, National Institute of Technology Raipur (NIT), India, for their invaluable motivation. Neeraj Kumar also sincerely thanks Dr. R. D. Patidar, Hon. Vice-Chancellor, OP Jindal University (OPJU), and Dr. S. Das (Former Director, CSIR-AMPRI, Bhopal), Steel Chair Professor and Head, Metallurgical Engineering Dept. for their outstanding involvement and motivations.This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (Nos. 2021R1A2C1005478 and 2021R1A4A1031357 ). Neeraj Kumar thanks Prof. Manoj Chopkar, Metallurgical and Materials Engineering Dept., and Prof. Ayush Khare, National Institute of Technology Raipur (NIT), India, for their invaluable motivation. Neeraj Kumar also sincerely thanks Dr. R. D. Patidar, Hon. Vice-Chancellor, OP Jindal University (OPJU), and Dr. S. Das (Former Director, CSIR-AMPRI, Bhopal), Steel Chair Professor and Head, Metallurgical Engineering Dept., for their outstanding involvement and motivations.
