National Conference on Advances in Mechanical Engineering Science (NCAMES-2016)

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1 A Study on Machinability of Hybrid Metal Matrix Composites-A Review Naveen C R 1, Dr. Thomas Pinto 2 1 Assistant Professor, Mechanical Department, Srinivas Institute of Technology, Mangaluru, India. 2 Professor, Mechanical Department, Srinivas Institute of Technology Mangaluru, India. Abstract In the present study, based on the literature review, the machining of hybrid Aluminium metal matrix composite is discussed. These hybrid HMMCs can easily be machined by conventional machining and good surface quality can be obtained by controlling the machining parameters. These Aluminium metal matrix composites with multiple reinforcement are finding increased applications because of improved mechanical and tribiological properties and hence are better substitutes for reinforced composites. These materials are developed for bushes, bearings and cylinder liners in cast Aluminium engine blocks. The problems encountered during machining of hybrid MMCs and their amendments by the use of conventional machining are discussed. Keywords Metal Matrix Composites, Conventional Machining, Hybrid Metal Matrix Composites (HMMCs). I. INTRODUCTION A study of the history, status, and opportunities of metal matrix composites is presented by evaluating the progression of available literature. The trends that existed and issues that still prevail are discussed and a prediction of the future for MMCs is presented. In many developed countries and in several developing countries there exist continued interest in MMCs. Researchers tried numerous combination of matrices and reinforcement since work on MMCs began in 1950s. These leads to developments for aerospace, but resultant commercial applications were limited. The introduction of ceramic whiskers as reinforcement under the development of insitu eutectics in the 1960s aided high temperature applications in aircraft engines. In the late 1970s the automobile industries started to take MMCs seriously. In the last 20 years, MMCs evolved from laboratories to a class of materials with numerous applications and commercial markets. So as to enhance further the properties of MMCs more than two materials were added in the matrix such that to give birth to hybrid metal matrix composites. There have been tremendous strides in engineering materials since the Second World War, researchers from various manufacturing, metallurgy, aerospace and nuclear industries developed large number of alloys. Since long back, metal matrix composites were introduced in the aerospace and aeronautics industries and later on reached to the automotive industry. However, MMCs are not widely used in these industries because of their poor performance in context of Machinability. Such materials can only be machined, if we understand the reasons for their poor Machinability and take effective measures to counter them. Metal matrix composite are composed of metal matrix and reinforcement, or filler materials, which confers excellent mechanical performance, and can be classified according to whether the reinforcement is continuous or discontinuous, The principal matrix materials for MMCs are Aluminium and its alloys. To a lesser extent magnesium and titanium are also used and for several specialized applications a copper zinc or lead matrix may be employed, MMCs with discontinuous reinforcement are usually less expensive to produce than continuous fiber reinforced MMCs, although this benefit is normally offset by their inferior mechanical properties. Consequently continuous fiber reinforced MMCs are generally accepted as offering the ultimate in terms of mechanical properties and commercial potential. In general, the major advantages of Aluminium Matrix Composites over monolithic materials example iron, steel and other non ferrous common metals are as follows: High specific strength High specific stiffness Higher elevated temperature strength Improved wear resistance Low density High strength to weight ratio Improved damping capabilities Tailor able thermal expansion coefficient Good corrosion resistance etc, When at least three materials are present it is called a hybrid composite, Al/SiC/Gr particle, MMC is one of the important hybrids among MMCs which have SiC and Gr particle with aluminium matrix, the SiC is harder than Tungsten carbide and graphite particle provide high resistance to wear in the hybrid composite. Recently modern industry rapidly introducing different composites due to their unique properties such as low density and very light weight with high temperature strength, hardness and stiffness, high fatigue strength and wear resistance, in order to meet the challenge of liberalization and to ISSN: Page 353

2 maintain global competitiveness in the market. Side by side modern manufacturing engineers are also trying to introduce the better properties in the composite like hybriding our usually available conventional composites such a Al/SiC/Gr particle etc. the hybrid metal matrix composite like Al/(SiC p +Gr p )-MMC is one of the composites which have many unique properties over Al/SiC-MMC or Al/Gr p -MMC. The wear resistance of Al/SiC/Gr p composite increases with the increase of the graphite particle size. The improvement of wear resistance is mainly attributed to the enhancement of integrity of lubrication tribo layer composed of a complex mixture of graphite as well as fracture SiC particles and some fine particles containing aluminium [7]. The aluminium alloy, reinforced with discontinues ceramic reinforcements, is rapidly replacing conventional materials in various automotive, aerospace and automobile industries. Most of the parts obtained with aluminium matrix composites through different manufacturing processes namely the process derived from the casting have different geometry and they usually need machining operations with the required dimensional and geometrical precision as well as good surface roughness[5]. From literature review, it is understood that the researchers have been used various methods to machine composite materials but the production of complex shapes, groves, blind holes, dovetail accuracy on Al/SiC/Gr p -MMC composite parts have also been difficult to obtained with traditional machining process. From the published research work it is also clear that the MMCs are much more difficult to machine than any monolithic materials by conventional or non conventional machining techniques. Harder cutting tool materials then work piece materials are the basic requirement in conventional methods of machining in manufacturing in which the work piece is converted into finished product or components of specific dimensional accuracy, size and shape and while achieving required configuration with the interaction of harder cutting tool material. But in SiC particles are harder than tungsten carbide which itself is a common cutting tool material in most of the cutting operations of hard materials, Al/SiC/Gr p -MMCs particles are having very high values of hardness and stiffness, the selection of proper cutting material and method of machining for machining of such hard composites have really been very difficult. Al/SiC/Gr p composites can be used in automobile components like a piston, cylinder blocks for automobile engines that operate at a temperature upto C. It is understood that it is difficult to make a quantitative comparison of the literature data, since the wear rate and friction coefficient strongly depend upon the testing method, testing environment, testing variables composite manufacturing route and there enforcement volume fraction, size and hardness, it is due to excessive cutting tool wear, diffusion occurs, built-up edges formed during conventional machining and formation of researchers poor surface finish etc. through conventional machining process, machining of Al/SiC/Gr p -MMCs encountered many problems by the researchers. The problems encountered during the processing of Al/SiC/Gr and Al/Al 2 O 3 MMCs in manufacturing industry through conventional machining are irregular material removal rate, required large current, poor surface finish, tool wear rate etc. these problems restricted the wide spread application in manufacturing, aerospace, and automotive industry[12].. II. LITERATURE REVIEW A study conducted by Manna A. and Bhattacharyya B. studied the machiniability of Al/SiC-MMC. The impact of machining parameters such as cutting speed, feed and depth of cut investigated the SEM micrographs BUE and chip formation at different sets of experiments were examined. Author conclude that flank wear rate is aversively proportional to cutting speed due to generation of high cutting force and formation of BUE[1]. A study conducted by Manna A. and Bhattacharyya B. Experimentally investigated the influence of cutting conditions on surface finish during turning of Al/SiC-MMC. In this study the taguchi method a powerul tool for experiment design was used to optimize the cutting parameters for effective turning of Al/SiC-MMC using a fixed rhombic tooling system [4]. A study conducted by Manna A and Bhattacharya B experimentally studied the Machinability of Al/SiC-MMC by utilizing CNC- Wire cut EDM. Authors studied the various parameters of WEDM during machining and established the optimum combination of WEDM parameters for different performance criteria. It was concluded that low input pressure of dielectric is not sufficient to remove the reinforced particles during machining. Open gap voltage and pulse on time are the most significant and influenceing machining parameters for controlling the material remove rate [2]. A study conducted by Mohammad Jafar Haddad and Alireza Fadaei Thrani, experimentally investigated the influence of cutting conditions on surface, roundness and material removal rate of tool steel. Authors used factorial design in DOE( Design of experiment) technique to find the impact of machining parameters. It was concluded that surface roughness and material removal rate is directly proportional to power and voltage and are inversely proportional to pulse on time and spindle rotational speed. Author then used regression analysis to generate a model of high stability [3]. ISSN: Page 354

3 A study conducted by Vibu Nanthan.M, Vidhusan.C, and Vignesh.S.This paper presents the detailed discussions on machining of Aluminium - silicon carbide (10% by weight of particles) and boron carbide (5% by weight of particles) Hybrid Metal Matrix Composites (Al/SiC/B4C MMC).SiC and a BC particle range from 40µm to 80 µm. The cylindrical rods of diameter 65 mm and length 200 mm are fabricated and subsequently machined using medium duty lathe of 2 kw spindle power to study the machinability issues of Hybrid MMC using Poly Crystalline Diamond insert of 1600 grade. The optimum machining parameters have been identified by Analysis Of Variance. Confirmation test is also conducted to validate the test result. Experimental results have shown that machining performance can be improved effectively through this approach. Results show at higher cutting speeds, good surface finish is obtained with faster tool wear. It is concluded that, tool wear and cutting force are directly proportional to the cutting speed, where as surface roughness is inversely proportional to cutting speed [11]. A study conducted by V.L. Kingston, Prabhakar, Dr. N. Senthilkumar. In the present study, the effect of Silicon carbide, Boron carbide on Stir cast Aluminum Metal Matrix Composites is discussed. Graphite is used as a lubricant. Aluminum Metal Matrix Composites with Silicon carbide and Boron carbide particle reinforcements are finding increased applications in aerospace, automobile, space, underwater, and transportation applications. The hybrid metal matrix composite which consists aluminum and other constituents such as graphite, silicon carbide and boron carbide are to be casted and are further employed to different testing such as hardness test, compression test, tensile test, impact test, micro hardness and micro structural analysis. Further it is machined to know its characteristics. Conventional stir casting process has been employed for producing discontinuous particle reinforced metal matrix composites [12]. In this paper, an attempt has been made by Sahib Singh, Kapil Singh to experimental investigation the machinability of aluminum metal matrix composite (LM13/SiC/15p) during continuous turning of composite rods using carbide inserts. Base matrix material is Aluminium LM13 reinforced with 15 % weight by volume of Silicon carbide particles of mean diameter 20 µm to 40 µm is used. The main focus of investigation is to determine surface roughness. Experiments were conducted in the CNC lathe by using carbide insert at various cutting conditions and parameters such as cutting speed, feed and depth of cut and surface roughness was found at different levels. The effect of machining parameters, e.g. cutting speed and depth of cut on the surface roughness investigated during experimentation [13]. This study presents by S. Basavarajappa an experimental investigation on tool wear in machining Al 2219/15SiCp and Al 2219/15SiCp- 3Gr (hybrid) composites at different cutting conditions with carbide, coated carbide, and polycrystalline diamond (PCD) tools. An attempt is made in the present investigation to study the effect of graphite incorporation in Al 2219/15SiCp composite on tool wear. The results reveal that the incorporation of graphite in Al 2219/15SiCp composite reduces tool wear at all cutting conditions. This is due to graphite, which reduces the coefficient of friction between tool and work piece and between tool and chip interface. PCD tool performs better than carbide and coated carbide tools [14]. A study by Mohammad Jafar Haddad and Alireza Fadaei Thrani (2008), experimentally investigated the influence of cutting conditions on surface finish, roundness and material removal rate of tool steel. Authors used factorial design in DOE (Design of experiment) technique to find the impact of machining parameters. It was concluded that surface roughness and material removal rate is directly proportional to power and voltage and are inversely proportional to pulse on-time and spindle rotational speed. Author then used regression analysis to generate a model of high stability [9]. A study by G. Rajaram, S.Kumaran. Studied the behavior of composite at higher temperature by adding graphite to the composite. The Al Si/graphite composite can perform well up to 300 C, but the alloy can withstand till 250 C. During direct metal to metal contact, the graphite particles from composite pin surface forms a thin tribo film between surfaces. Tearing and formation of oxide layer and graphite film is a continuous process which results in decrement of wear rate for composite, when the operating temperatures are increased [5]. A study by S. Suresha, B.K. Sridhara. found that experimentally addition of Grp particulates facilitates easy machining and results in reduced wear of Al Grp composites compared to Al alloy. But high amount of Grp may result in increase of wear due to decrease in fracture toughness with increase in % reinforcement of Grp particulates. In tribological applications demanding similar strength requirement, Al SiC Grp hybrid composites are better substitutes to Al Grp and Al SiC composites owing to improved wear resistance as a result of combined reinforcement of SiC and Grp particulates [8]. A study by L.Krishnamurthy, B.K. Sridhara, D. Abdul Budan. Present result of an experimental investigation on the comparative machinability of aluminum-silicon carbide composites and aluminum-graphite-silicon carbide hybrid composites during turning using carbide tool inserts. The experiments have been carried out based on central composite design of experiments approach. ISSN: Page 355

4 The influence of machining parameters viz. cutting speed, feed and depth of cut on the resultant force has been analyzed statistically. It is established that hybrid composites have better machinability when compared to Al/SiC composites [7]. This study presented by S. Suresha, B.K. Sridhara. Shows that Aluminum matrix composites with multiple reinforcements (hybrid AMCs) are finding increased applications because of improved mechanical and Tribological properties and hence are better substitutes for single reinforced composites. Dry sliding wear tests have been performed to study the influence of Gr particulates, load, sliding speed and sliding distance on the wear of hybrid composite specimens with combined % reinforcement of 2.5%, 5%, 7.5% and 10% with equal weight % of SiC and Gr particulates. Experiments are also conducted on composites with % reinforcement of SiC similar to hybrid composites for the sake of comparison. Parametric studies based on design of experiments (DOE) techniques indicate that the wear of hybrid composites decreases from g to g as the %reinforcement increases from 3% to 7.5%. But the wear has a tendency to increase beyond % reinforcement of 7.5% as its value is g at.% reinforcement of 10%. This trend is absent in case of composites reinforced with SiC alone. The values of wear of these composites are g, g and g, respectively, at. % reinforcement of 3%, 7.5% and 10% clearly indicating that hybrid composites exhibit better wear characteristics compared to composites reinforced with SiC alone [6]. III. RESULTS & DISCUSSIONS Best machining parameter was determined as cutting speed 100 m/min, feed rate 0. 1mm/rev and depth of cut 0.5 mm (experimental reading number 1). Now setting this cutting condition as a constant parameter and machined the samples for a time duration of 30minutes and the tool flank. Wear study was carried out. Tool was monitored for normal types of wear namely flank wear, crater wear and nose wear using a tool maker s microscope. Tool flank wear was caused by abrasive nature of the hard particles present in the work piece [11]. At low cutting speed worn flank encourages the adhesion of work piece material on the tool insert and formed Built-Up-Edge shows the Scanning Electron Microscope (SEM) image of fresh insert. Shows SEM image of PCD 1600 grade insert after machining the work piece for 30 minute duration. It is proved that hard silicon and boron carbide particles which have higher hardness than diamond abrading the cutting tool It is observed that the tool life of PCD 1600 grade is performing well in the chosen cutting condition. Fig. 1 SEM Image of Fresh PCD 1600 grade Fig. 2 worn out insert after 30min duration It is clearly understood that, cutting speed has high contribution on power consumed (57.34%), followed by feed (25.888%) and depth of cut (8.99%). It is also observed that interaction effect of cutting speed and feed has sizeable contribution on power consumed (3.92%). ISSN: Page 356

5 Fig. 5 Cutting speed v/s R a Fig. 3 Main effect plot for surface roughness It is clearly understood that, cutting speed has high contribution on cutting force (43.58%), followed by feed (36.66%) and interaction effect of cutting speed and feed (12.74%). It is also observed that depth of cut has sizeable contribution on surface roughness (1.69%). From graph of a Vs. Depth of cut when speed = 150 m/min & feed = 0.3 mm/rev, it is observed that when speed & feed are kept constant & only depth of cut is increased continuously then surface roughness also increases continuously. Also spindle load increases continuously with cutting speed. Maximum value of spindle load occurs when value of depth of cut is high. Fig. 7 Depth of Cut v/s R a Fig. 4 Main effect plot for cutting force Material LM13 composition. It has got low thermal expansion and good wear resistance. It is observed that while machining LM13 work piece, discontinuous chips are formed. Experimental data related to surface roughness characteristics three graphs are plotted [13]. It is observed from the Graph of Ra Vs Speed at Feed=0.3 mm/rev & Depth of Cut=0.6 mm that when feed & depth of cut are kept constant & only speed is increased continuously after certain maximum value of 250 m/min then we can obtain a sudden increase in the surface roughness. This is not the usual case in case of Al composites but in this experimental work, surface roughness is minimum at cutting speed of 100 m/min and maximum at 250 m/min. VI. CONCLUSIONS From the above literature review, it is clear that there is essential need to select proper machining process for effective machining of hybrid Al/SiC/Gr and Al/Al 2 O 3 /Gr-MMC. As such no sufficient number of literature on machining of hybrid Al/(SiC+Gr)-MMC is available, but from the published research work it is clear that the Al/SiC- MMC machining is one of the major problem, which resist its wide spread application in industry. REFERENCES 1. Manna and Bhattacharyya B, A study on machinability of Al/SiC-MMc, Journal of material processing technology, Vol. 140,(2013) pp Che Chung Wang, Cutting Austempered ductile iron using an EDM sinker, Journal of material processing technology vol, 88, (1999), pp S. Clijsters and K.Liu,: EDM technology and strategy development for the manufacturing of complex parts in SiSiC, Journal of material processing technology Vol, 210, (2010), pp Manna A. and Bhattacharyya B.; Investigation for optimal parametric combination for achieving better ISSN: Page 357

6 surface finish during turning of AlSiC-MMC, International journal of Advance Manufacturing Technology, Vol. 23, (2004), pp G. Rajaram, S.Kumaran.; Studies on high temperature wear and its mechanism of Al Si/graphite composite under dry sliding conditions. Tribology International 43 (2010) S. Suresha, B.K. Sridhara.; Wear characteristics of hybrid aluminum matrix composites reinforced with graphite and silicon carbide particulates Composites Science and Technology 70 (2010) L. Krishnamurthy, B.K. Sridhara, D. Abdul Budan.; Comparative study on the machinability aspects of aluminium silicon carbide and aluminumgraphite-silicon carbide hybrid composites International Journal of Machining and Machinability of Materials Vol. 10, No.1/2 pp S. Suresha, B.K. Sridhara,; Effect of addition of graphite particulates on the wear behaviour in aluminium silicon 9. carbide graphite composites Elsevier, Kidlington, ROYAUME-UNI (1982) (Revue) 2010, vol. 31, no4, pp Jinfeng Leng, Longtao Jiang, Qiang Zhang, Gaohui Wu, Dongli Sun and Qingbo Zhou,; Study of machinable SiC/Gr/Al composites Journal of Materials Science (October 2008), 43 (19), pg Farshad Akhlaghi, S. Mahdavi,; Effect of the SiC Content on the Tribological Properties of Hybrid Al/Gr/SiC Composites Processed by In Situ Powder Metallurgy (IPM) Method 2011, Advanced Materials Research, , Vibu Nanthan. M, Vidhusan.C.; Machinability studies of turning Al/SiC/B 4C HMMCs using ANOVAs analysis, ICTMME 2012 July 15-16, Singapore. 13. V.L. Kingston, John Prabhakar,; A study on mechanical and machinability characteristic of HMMCs, IJERA (March 2014), ISSN: Sahib Singh, Kapil Singh,; Machining response in turning Aluminium composite LM13 with 15% SiC, IJERSTE, Vol. 1, Issue 1, oct S. Basavarajappa,; Tool wear in turning of composite HMMCs, Taylor & Francis (2009), pp ISSN: Page 358