Tribology in Industry Friction and Wear Properties of Rapid Solidified H-Al
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Vol. 42, No. 4 (2020) 529-546, DOI: 10.24874/ti.870.04.20.09 Tribology in Industry www.tribology.rs RESEARCH Friction and Wear Properties of Rapid Solidified H-Al-17Si Alloys Processed by UV Assisted Stir - Squeeze Casting with DLC-Star (CrN + a-c:H) Coating Under HFRR N.D. Malleswararao. Ka,*, I.N. Niranjan Kumarb, Bh. Nageshc aDepartment of Marine Engineering, Andhra University, Visakhapatnam, A.P, India, bDepartment of Marine Engineering, Andhra University, Visakhapatnam, A.P, India, cIndian Maritime University, Visakhapatnam, Andhra Pradesh, India. Keywords: A B S T R A C T Stir-squeeze casting Tribological properties of rapid solidified hyper eutectic AlSi17Cu3.5- AlSi MMC 4Mg0.6-0.8 (H-Al-17Si) alloy were investigated under different loading DLC-star coating conditions. The alloy was produced by the rheo-stir squeeze casting Friction process with the T-6 condition. Experimental studies were conducted using Wear high frequency linear reciprocating rig (HFRR) with a ball-on-plate geometry. The effect of applied load (10-50 N) on the wear and friction * Corresponding author: (COF) coefficients were studied under dry, lubricated (SAE15W40), and coated dry (DLC-Star) sliding conditions. For dry and lubricated sliding, N.D. Malleswararao. K COF values of hyper eutectic AlSi17Cu3.5-4Mg0.6-0.8 alloy were 0.26 and E-mail: [email protected] 0.042. A lower COF value of 0.013 was recorded with DLC-star (CrN + a- Received: 7 April 2020 c:H) coating under dry condition. Whereas, the least wear coefficient is Revised: 22 May 2020 also observed with DLC-star coating (4.6X10-5 mm3/N.m) compared to the Accepted: 5 September 2020 dry and lubricated sliding conditions (2.7X10-3 mm3/N.m and 3.8X10-4 mm3/N.m). The developments in COF and wear coefficients were mainly attributed to the distribution and size of primary Si granules and the formation of transfer layers on the coated surfaces of AlSi17Cu3.5-4Mg0.6- 0.8 alloy. Surface morphologies were examined using SEM, AFM, surface roughness profilometer, and advanced metallurgical microscope (AMM) analysis techniques. © 2020 Published by Faculty of Engineering 1. INTRODUCTION controlled by several factors, including lubricants, surface structure, contact geometry, The performance of an automobile engine speed, distance, and load [2]. Over the past few depends much on tribological properties and decades, researchers have developed numerous emission losses [1]. However, the tribology of a wear and friction solutions in terms of nano- mechanical system is very difficult, being lubricants, surface coatings, lightweight 529 N.D. Malleswararao. K et al., Tribology in Industry Vol. 42, No. 4 (2020) 529-546 composites, for the manufacturing of high the solutions for reducing wear and friction in performance engine components to enhance automobile components is lubricant oils [29]. efficiency, reduce emission, wear and friction Dey et al. executed tribological studies on Al-Si losses [3-5]. (18.5 wt%) MMCs by varying load 0.5–5 N under the lubricated condition and found that few In the last 20 years, hypereutectic Al-Si alloys scratch marks are only left on the surface by Si (H-Al-Si MMCs) are promising materials to particles, and alloy matrix was glued to the increase efficiency and reduce emissions [6,7]. counterpart when the load increased [30]. Later, H-Al-Si MMCs possess excellent thermal Parveen Kumar et al. investigated the resistance, corrosion resistance, abrasion tribological behavior of AlSi25 MMC with resistance, and high specific strength [8-10]. different loading conditions (5-100 N) under Whereas, the traditional cast H-Al-Si alloys lubricated and dry conditions using an LRT reached their limits of resisting heat and (linear reciprocating tribometer). In this study, it elevated temperature strength as the engine was noticed that with lubricating oil power increased [11]. Thus the researchers (SAE20W40) remarkable reduction in COF and developed new casting techniques including wear coefficient is achieved [31]. Further, the spray deposition, powder metallurgy, and planar investigation continued by varying load 100-300 flow casting on rapid solidification to prepare N and stated that at excessive loads, the MMC Si- high strength and high heat resistant Al alloys particles were jutted out then mixes with [12,13]. However, these new techniques are lubricating oil and performs as a solid lubricant challenging to execute, and the dimensions of which results in substantial improvement in COF the components are also limited [11]. The use of and wear rate [32]. However, these conventional ultrasonic vibration during the stirring of Al-Si lubricants cannot withstand the latest higher- MMCs and squeeze is a comparatively new powered engines for a long time at extreme method [14]. It is a user-friendly technique with loads and temperatures; the need for developing the benefits of low cost and simple operability high-performance lubricating fluids is [15-18]. Vineet Tirth et al. and Khemraj et al. significantly increasing. explored the effect of stir-squeeze casting on the tribological properties of hybrid aluminum Scholars examined the tribological behaviors of matrix composite. They reported that the stir- nanoparticles as lubricant oil additives. It has squeeze casting process substantially improved been found that the reinforcement of the hybrid composite [19-22]. H-Al-Si alloys are nanoparticles into the lubricating oil improves usually characterized as the composite where Si the load-carrying capacity and reduces COF and percentage is equal to or greater than 17 wt%. wear rate [33-35]. However, at raised The addition of Si like hard particles enhances temperatures, large protuberances founded on the hardness, which in turn improves the alloys the counterpart surfaces may increase wear and (H-Al-Si) wear-resisting properties [23, 24]. friction coefficients. To solve this problem, Clarke et al. explored the wear behavior of Al-Si researchers tend to add fullerene (IF-Mos2 and metal matrix composites (MMC = alloy) by h-BN) like nanoparticles into the lubricant changing Si weight percentage (up to 21 wt%) liquids (SAE15W40), reported that the and stated that the hyper eutectic MMCs have low reinforcement of IF-Mos2 and h-BN nano wear resistance than hypoeutectic MMCs [25]. granules into the lubricating oil enhances the However, Reddy et al. carry out some wear tests anti-wear and friction properties remarkably on a series of MMCs (AlSi) changing Si weight [36-39]. From the above literature, it is observed percentage up to 23 wt% and addressed that the that the reinforcement of nanoparticles into the reinforcement of hard primary Si particles to lubricating oil improves the COF and wear alloy matrix enhances wear resistance of H-Al-Si performance of automobile components. MMCs [26]. Thus the reinforcement of Si granules to the alloy matrix enhances both tribological and Though, the journey of finding a perfect mechanical properties. lubricant, which gives the least tribological properties, still proceeds [40]. An energizing Numerous tribological studies reported on the substance that has been examined broadly for its wear and friction characteristics of Al-Si MMCs vast number of tribological and mechanical [27,28]. Though, over the past few years, one of characteristics is Diamond-like carbon (DLC). In 530 N.D. Malleswararao. K et al., Tribology in Industry Vol. 42, No. 4 (2020) 529-546 general, these coatings (DLC) show excellent The present research aims at the effect of the corrosion resistance, higher hardness, high casting process and coatings on tribological thermal stability, and extreme tribological properties of hypereutectic aluminum-silicon properties. However, the friction and wear alloys, which are popularly used in the properties heavily influenced by temperature automotive industry. However, the use of DLC- and humidity [41-47]. Moreover, some studies Star coating with RSSC Al-Si alloy has not been show that the hydrogenated-amorphous DLC reported in published research. It is desirable to layers (a-C:H) are the promising wear and COF apply the coating on Al-Si alloys for better resistant coatings at different environmental friction and wear properties. The metal matrix conditions [48-50]. Erdemir et al. reported that composites (alloys) recognized for this research the hydrogen plays an essential role in are Al17Si3.5-4Cu0.6-0.8Mg, one of the widely determining the tribological characteristics of used alloys in the automobile industry. The DLC coatings due to preventing graphitization alloys have good potential for higher and formation of stabilized sp3 tetrahedral temperatures, hardness, and wear applications bonds. However, a-C:H coatings show excellent in production and automobile industries. tribological properties for Al alloys at the However, the coatings identified for this study ambient conditions compared to the other have been deposited by a combined PVD/PACVD coatings like CrN and TiN [51-56]. Besides, few method, which has been selected based on the scholars investigated the performance of DLC literature review. coatings on Al-alloys with inert gas and dry nitrogen environmental conditions and reported that the reduction in friction coefficient (0.001- 2. EXPERIMENTAL DETAILS 003) is remarkable, and the wear rate (10-10–10- 11 mm3/Nm) was improved mainly [44,45,57]. 2.1 Materials and specimens preparation Later, researchers conducted several experiments on a-C:H films at elevated The hyper eutectic AlSi17Cu3.5-4Mg0.6-0.8 (H- temperatures and reported that the COF Al-17Si) alloy was prepared by using rheo stir- decreases, and the wear scars become deeper, squeeze (rheo = ultrasonic vibration (UV) bigger, and softer [58-69]. From these studies, it assisted) casting technique under T-6 condition is clear that the DLC coating has extraordinary (RSSC-T6). However, the H-Al-17Si alloy (Table potential as a hard film to combat COF and wear 1) was processed with stir casting with UV rate in different tribological uses.