A study on wear behaviour of Al/6101/graphite composites J F A P D a b c d a A R R 2 A A K C C H S W 1 r a l N p i t c r T s a w h 2 l ARTICLE IN PRESSG Model ASCER 254; No of Pages 7 Journal of Asian[.]
G Model JASCER-254; No of Pages ARTICLE IN PRESS Journal of Asian Ceramic Societies xxx (2017) xxx–xxx Contents lists available at ScienceDirect Journal of Asian Ceramic Societies journal homepage: www.elsevier.com/locate/jascer Full Length Article A study on wear behaviour of Al/6101/graphite composites Pardeep Sharma a,∗ , Krishan Paliwal a , Ramesh Kumar Garg b , Satpal Sharma c , Dinesh Khanduja d a Panipat Institute of Engineering and Technology, Panipat, India D.C.R University of Science and Technology, Murthal, Sonipat, India Gautam Buddha University, Greater Noida, India d National Institute of Technology, Kurukshetra India b c a r t i c l e i n f o Article history: Received 13 October 2016 Received in revised form 22 December 2016 Accepted 26 December 2016 Available online xxx Keywords: Casting Composites Hardness Strength Wear a b s t r a c t The current research work scrutinizes aluminium alloy 6101-graphite composites for their mechanical and tribological behaviour in dry sliding environments The orthodox liquid casting technique had been used for the manufacturing of composite materials and imperilled to T6 heat treatment The content of reinforcement particles was taken as 0, 4, 8, 12 and 16 wt.% of graphite to ascertain it is prospective as self-lubricating reinforcement in sliding wear environments Hardness, tensile strength and flexural strength of cast Al6101 metal matrix and manufactured composites were evaluated Hardness, tensile strength and flexural strength decreases with increasing volume fraction of graphite reinforcement as compared to cast Al6101 metal matrix Wear tests were performed on pin on disc apparatus to assess the tribological behaviour of composites and to determine the optimum volume fraction of graphite for its minimum wear rate Wear rate reduces with increase in graphite volume fraction and minimum wear rate was attained at wt.% graphite The wear was found to decrease with increase in sliding distance The average co-efficient of friction also reduces with graphite addition and its minimum value was found to be at wt.% graphite The worn surfaces of wear specimens were studied through scanning electron microscopy The occurrence of wt.% of graphite reinforcement in the composites can reveal loftier wear possessions as compared to cast Al6101 metal matrix © 2017 The Ceramic Society of Japan and the Korean Ceramic Society Production and hosting by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/) Introduction Conventional aluminium metal matrix and its alloy show a receptacle protagonist in various technological areas such as aerospace, marine, nuclear, structures and automobile due to its low weight to strength ratio and excellent mechanical properties Nevertheless, the punitive situation of aluminium alloy is that, they possess low resistance to abrasive wear in discrepancy lubricating environments and spartan preservation of lubricating film over the sliding surface, which turn out to be vain to tribological applications To increase their tribological properties, aluminium alloy reinforced with graphite particulate composites had been explored These Al/Graphite (self-lubricating) composites had been emphasized because of their anti-seizure influence [1–4], high damping absorption capacity, low coefficient of thermal expansion [5,6], low wear and coefficient of friction [7–11] and decreased tempera- ∗ Corresponding author E-mail address: pardeep84sharma@gmail.com (P Sharma) ture rise at wearing interaction surface [12] Previous investigators had conveyed that in dry sliding environments Al/Graphite composites resulted in to development of an incessant film of solid lubricant [13–20] which had been formed on tribo-surfaces This phenomenon happens as a consequence of cutting of graphite reinforcement particles which are situated underneath the sliding surface of composite, which assist in decreasing the extent of shear stress, which assuages the plastic deformation in the subsurface area, obstructs metal-to metal interaction and performs as solid lubricant between two sliding surfaces therefore decreasing wear, coefficient of friction and seizure resistance of the composites [18] Hence development and preservation of this tribo-layer on the sliding surfaces, gearstick the wear behaviour of the composites by its features like; area of fracture, composition, thickness and hardness Tribo-layer formation depends upon the nature of sliding surfaces, content of graphite and environment (dry/lubricated) in the composite It had been explored that increasing the content of graphite reinforcement in Al/Graphite composites, wear rate of composite lowered [11,17,18] Besides this, wear rate also simultaneously increased with increase in the volume fraction of graphite http://dx.doi.org/10.1016/j.jascer.2016.12.007 2187-0764/© 2017 The Ceramic Society of Japan and the Korean Ceramic Society Production and hosting by Elsevier B.V This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Please cite this article in press as: P Sharma, et al., A study on wear behaviour of Al/6101/graphite composites, J Asian Ceram Soc (2017), http://dx.doi.org/10.1016/j.jascer.2016.12.007 G Model ARTICLE IN PRESS JASCER-254; No of Pages P Sharma et al / Journal of Asian Ceramic Societies xxx (2017) xxx–xxx Table Chemical composition of base metal AA6101 Constituent Al Si Mg Cu Mn Cr Fe Zn Content (wt.%) 97.6 0.30–0.70 0.35 0.10 0.03 0.03 0.50 0.10 Fig The line layout of three point bending test Fig Casting facility used to prepare Al6101/Graphite AMCs reinforcement because of decrease in hardness and toughness of Al/Graphite composites [11,18–24] In various conditions, transition of wear rate from mild to severe range takes place as a result of effect of graphite content in Al/Graphite composites Therefore this research work aims to assess the influence of graphite on the tribological behaviour of Al6101/Graphite composites, in terms of rate of wear and coefficient of friction in dry sliding environments; and to estimate the optimum volume fraction of graphite addition in Al6101 Experimental procedure Aluminium Al6101 of commercial grade was used as the matrix material and graphite particles with size varying from 26 to 30 m was used as the reinforcement material Table displays the chemical composition of Al6101 used in this research work An orthodox casting technique was used for the manufacturing of composites Set-up for stir casting technique is displayed in Fig The proper amount of Al6101 was heated in a graphite crucible placed in an electric furnace The graphite was also preheated to 720 ◦ C with the help of a separate electric furnace After melting the Al6101 in the electric furnace, graphite reinforcement particles (preheated) were added and mixed molten mixture was stirred at 550 rpm for 10 by using an electric motor which is fitted with a mechanical stirrer The temperature was kept constant (800 ◦ C) during whole stirring The molten aluminium alloy split into droplets because of shear force imparted by the stirrer at the presence of graphite [18] Now the molten mixture was exiled from the graphite crucible into a permanent preheated (500 ◦ C) steel mould The molten mixture was allowed to solidify in steel mould The casted composite was subjected to T6 heat treatment Heat treated composite was tested for various tests The same procedure was followed to manufacture all other composition The composites were manufactured at 0, 4, 8, 12 and 16 wt.% of graphite reinforcement particles Hardness measurement was carried out on a Vickers hardness testing machine with a load of 500 g and mean values of atleast five measurement from different areas on specimen were taken The specimen for tensile test was made in accordance with ASTM E08 standard [25] A distinctive tensile specimen is displayed in Fig The ultimate tensile strength was evaluated on computerized universal testing machine (HITECH TUE- C-1000, India) [26] The flexural strength was assessed with the help of three point bending test (Fig 3), to know the extreme load which the composite can withstand Wear samples were prepared according to ASTM G99-95 standards, the wear tests were conducted using Pin-ondisc apparatus (Fig 4) at room temperature (35 ◦ C) and humidity 55–65% The wear tests were conducted at 0.4, 0.8, and 1.2 m/s sliding speed and 15, 30, and 45 N applied loads and with 1200 m as the sliding distance for 300 m as regular intervals Wear samples (pins) with 50 mm height and mm diameter were used for the wear test The end surface of the wear test pins was properly cleaned and polished with abrasive papers of grades 400, 600, 800, 1000, and 1200 respectively The wear rate was measured by weight loss method The weight of the each wear sample was measured using an electronic weighing balance with resolution of ±0.1 mg Scanning Electron Microscopy (Surpa 40 VP Bruker System, Germany) was used for examining the morphology of the worn surfaces of the wear specimens Results and discussion Fig displays a reduction in hardness with increase in volume fraction of graphite reinforcement particles in Al6101 This decrease in hardness may be due to low hardness of graphite of 25.49 VHN as compared to 47.9 VHN of aluminium Further the brittle nature of graphite due to increased content causes the composites to deform plastically This behaviour is in good agreement with the results of previous researchers [9,18,19,27–30] The ultimate tensile strength (UTS) decreased from 164 MPa to 147 MPa (Fig 6) with a linear increase in graphite content in Al6101 Fig Typical tensile test specimen Please cite this article in press as: P Sharma, et al., A study on wear behaviour of Al/6101/graphite composites, J Asian Ceram Soc (2017), http://dx.doi.org/10.1016/j.jascer.2016.12.007 G Model ARTICLE IN PRESS JASCER-254; No of Pages P Sharma et al / Journal of Asian Ceramic Societies xxx (2017) xxx–xxx Microhardness (VHN) Fig A schematic diagram of pin on disc apparatus 49 48 47 46 45 44 43 42 Wt % of graphite addition 12 16 UTS (MPa) Fig Variation of micro-hardness with weight percentage of graphite addition 170 165 160 155 150 145 140 135 12 Wt % of graphite addition 16 Fig Variation of UTS with weight percentage of graphite addition This reduction in UTS may be due to existence of graphite reinforcement particles which due to their low hardness and brittle nature imparted brittleness in the composites due to which composites offer low resistance to the tensile stress produced [28] The percentage elongation (Fig 7) also decreased as the content of graphite increased in Al6101 The brittle behaviour of the reinforcing parti- Please cite this article in press as: P Sharma, et al., A study on wear behaviour of Al/6101/graphite composites, J Asian Ceram Soc (2017), http://dx.doi.org/10.1016/j.jascer.2016.12.007 G Model ARTICLE IN PRESS JASCER-254; No of Pages P Sharma et al / Journal of Asian Ceramic Societies xxx (2017) xxx–xxx % Elongation 4 12 16 Wt % of graphite addition Fig Variation of percentage elongation with weight percentage of graphite addition 90 Flexural Strength (MPa) 80 70 60 50 40 30 20 10 Wt % of graphite addition 12 16 Fig Variation of flexural strength with weight percentage of graphite addition 0.0009 Wear rate (mm3/N-m) 0.0008 0.0007 0.0006 0.0005 0.0004 0.0003 0.0002 0.0001 0 12 Wt % of graphite addition 16 Wear rate (mm3/ N-m) Fig Variation of wear rate with weight percentage of graphite addition 0.002 0.0018 0.0016 0.0014 0.0012 0.001 0.0008 0.0006 0.0004 0.0002 Cast Al6101 Wt % Graphite Wt % Graphite 12 Wt % Graphite 16 Wt % Graphite 15 30 45 Varying applied load in newton Fig 10 Variation of wear rate with varying applied load Please cite this article in press as: P Sharma, et al., A study on wear behaviour of Al/6101/graphite composites, J Asian Ceram Soc (2017), http://dx.doi.org/10.1016/j.jascer.2016.12.007 G Model ARTICLE IN PRESS JASCER-254; No of Pages P Sharma et al / Journal of Asian Ceramic Societies xxx (2017) xxx–xxx 0.001 0.0008 0.0009 0.0007 0.4 m/s 0.8 m/s 1.2 m/s 0.0006 0.0005 Wear rate (mm3/ N-m) Wear rate (mm3/ N-m) 0.0009 0.0004 0.0003 0.0002 0.0001 0.0008 0.0007 Al6101 Wt % Graphite 16 wt % Graphite Wt.% Graphite 12 Wt.% Graphite 0.0006 0.0005 0.0004 0.0003 0.0002 0.0001 12 16 0 Graphite content in Wt % 300 600 900 1200 Varying sliding distance (m/s) Fig 11 Variation of wear rate with varying sliding speed (a) Variation of wear rate with varying sliding distance at 0.4 m/s Co-efficient of friction Wear rate (mm3/ N-m) 0.0008 0.0007 0.0006 0.0005 Al6101 Wt.% Graphite Wt % Graphite 12 Wt.% Graphite 16 Wt % Graphite 0.0004 0.0003 0.0002 0.0001 0 300 600 900 1200 Varying sliding distance (m/s) (b) Variation of wear rate with varying sliding distance at 0.8 m/s 0.0008 Wear rate (mm3/ N-m) cles (graphite) performs a momentous protagonist in reducing the ductility because graphite as an indulgent reinforcement is brittle in behaviour and enlarged the brittleness in the aluminium matrix composites (AMCs) which actually reduced the ductility [29] The flexural strength of cast Al6101 metal matrix and manufactured composites are shown in Fig It is revealed from Fig that with rise in graphite content in Al6101, the flexural strength of composites decreased This decrease in flexural strength might be due to because of increase in graphite content in Al6101 results into increased tendency of initiation of crack and propagation at the interface between aluminium metal matrix (Al6101) and reinforcement particles (graphite) These results are in line with the investigations of earlier researchers [2,18] The wear rate of cast Al6101 and manufactured AMCs with varying wt.% of graphite reinforcement particles is shown in Fig The wear rate of AMCs decreases with increase in volume fraction of graphite reinforcement particles The value of wear rate was found to be lowest at wt.% of graphite reinforcement particles The value of wear rate at wt.% is lower than that of cast Al6101 and other manufactured composites Further than (after wt.%), the wear rate rises and it was found to be lower than that of the cast Al6101 This decrease in wear rate may be due to addition of graphite reinforcement particles which performs as a lubricant and it makes a tinny layer between the copulating surfaces This decreases the metal to metal interaction This behaviour of AMCs was in-line with the same results as observed by earlier researchers [18–24,31,32] wt.% graphite reinforced composites exhibits inordinate wear behaviour than that of the cast Al6101 and other manufactured AMCs With increase in graphite volume fraction i.e at higher graphite content, wear behaviour was perfectly reversed in its behaviour This decrease in wear rate might be because of increased graphite reinforcement content in Al6101 metal matrix which results into development of a tinny lubricating ridiculous film on the tribo surfaces, therefore increased graphite content resulted into enhanced cracks and porosity resulting into weakening of mechanical properties [8] It seems that the inserted graphite reinforcement particles in the AMCs performs as a lubricant through the abrasion process thereby decreasing the wear rate Al6101 Wt.% Graphite Wt % Graphite 12 Wt.% Graphite 16 Wt % Graphite 0.0007 0.0006 0.0005 0.0004 0.0003 0.0002 0.0001 0 300 600 900 1200 Varying sliding distance (m/s) (c) Variation of wear rate with varying sliding distance at 1.2 m/s Fig 13 (a) Variation of wear rate with varying sliding distance at 0.4 m/s (b) variation of wear rate with varying sliding distance at 0.8 m/s (c) Variation of wear rate with varying sliding distance at 1.2 m/s 0.5 0.4 0.3 0.2 0.1 0 12 Wt % of graphite addition 16 Fig 12 Variation of co-efficient of friction with weight percentage of graphite addition Please cite this article in press as: P Sharma, et al., A study on wear behaviour of Al/6101/graphite composites, J Asian Ceram Soc (2017), http://dx.doi.org/10.1016/j.jascer.2016.12.007 G Model JASCER-254; No of Pages ARTICLE IN PRESS P Sharma et al / Journal of Asian Ceramic Societies xxx (2017) xxx–xxx Fig 14 (a) Worn surface morphology of Al6101, (b) worn surface morphology of Al6101/4 wt.% graphite (c) worn surface morphology of Al6101/8 wt.% graphite (d) worn surface morphology of Al6101/16 wt.% graphite The wear rate rises with an escalation in the applied load and it grasps its lowest value at wt.% of graphite reinforcement particles as shown in Fig 10 Fig 11 shows the variation of wear rate with sliding speed, it is revealed that the wear rate of AMCs reinforced with graphite reinforcement particles reduces with an linear rise in sliding speed and wear rate was found to be optimum at wt.% of graphite in comparasion with other manufactured AMCs Fig 12 displays the relation between averages co-efficient of friction with various wt.% of graphite reinforcement particles It is observed that the average coefficient of friction reduces with increase in volume fraction of graphite content in Al6101 It is observed that the coefficient of friction of composite reinforced with wt.% graphite reinforcement particles is about 0.2, which is lower than that of graphite (0.42) in dry sliding environments With further increase in graphite content i.e after wt.%, the coefficient of friction reduces as compared to that of cast Al6101 This might be due to, increased graphite content which resulted into the formation of smeared graphite layer between the sliding surfaces [1,4,18], which performs as a solid lubricant The thickness of this graphite film/layer increases with increase in the volume fraction of graphite reinforcement particles The formation of this smeared graphite layer results in to reducing the coefficient of friction of AMCs and reduces the contact of wear pin to disc Therefore, it can be established that the addition of graphite to the Al6101 aluminium metal matrix improves the tribological behaviour of AMCs Wear rate and coefficient of friction of all man- ufactured AMCs is better than that of cast metal matrix and both Wear rate and coefficient of friction reduces significantly with the applicable volume fraction of graphite reinforcement It is also revealed that wear behaviour of manufactured AMCs depends upon the thickness of the graphite layer at tribo surfaces (Fig 12) Fig 13a–c displays the variation in wear rate under several dry sliding conditions i.e sliding speed 0.4, 0.8, and 1.2 m/s for 1200 m of sliding distance At these situations, composite with wt.% of graphite was found to exhibit lower wear rate than that of cast Al6101 metal matrix and all other composites In the worn morphology of Al6101/4 wt.% graphite (Fig 14b) various grooves has been noticed, the size of these grooves is smaller than that of present in cast Al6101 metal matrix (Fig 14a) Fig 14d, displays that the smeared layer converted into thicker and denser film as a result of an increase in volume fraction of graphite content i.e 16 wt.% in Al6101 After performing wear test, it was revealed that a lubricating film of graphite cover the whole worn surfaces uniformly, due to which direct contact of wear pin and disc has been prevented, thus efficiently decreases the coefficient of friction (Fig 14c) Fig 15 displays the influence of addition of graphite content on the transition load during the inception of severe regime over the cast Al6101 and manufactured AMCs From Fig 15, it was observed that severe wear takes place in the AMCs above 1.2 N load and maximum transition load had been taken place at 16 wt.% of graphite content with the Al6101 Please cite this article in press as: P Sharma, et al., A study on wear behaviour of Al/6101/graphite composites, J Asian Ceram Soc (2017), http://dx.doi.org/10.1016/j.jascer.2016.12.007 G Model ARTICLE IN PRESS JASCER-254; No of Pages P Sharma et al / Journal of Asian Ceramic Societies xxx (2017) xxx–xxx Transition load (N) 0 Wt % of graphite addition 12 16 Fig 15 Effect of graphite addition on the transition load for inception of severe wear regime Conclusions The hardness, ultimate tensile strength as well as percentage elongation reduces with increase in graphite content and their values are highest at lower wt.% of graphite i.e wt.% The flexural strength also reduces with increase in graphite content and it has attained its maximum value at wt.% of graphite The wear rate reduces with increase in graphite content and it was found minimum at wt.% of graphite, which exhibits the superior wear properties than that of cast Al6101 metal matrix and other composites Wear rate enhances with increase in applied load and this behaviour is due to pull out of graphite reinforcement particles from Al6101 metal matrix The wear rate of AMCs reduces with increase in sliding speed and enhances with increase in sliding distance Wear rate was found minimum at wt.% of graphite addition and lower than that of cast Al6101 This confirms that wear rate was optimum at wt.% of graphite addition to the Al6101 metal matrix [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] References [27] [1] [2] [3] [4] [5] [6] H.S Chu, K.S Liu and J.W Yeh, Mater Sci Eng., 277A, 25–32 (2010) G.M.L Ted and C.Y.A Tsao, Mater Sci Eng., 333A, 134–145 (2002) B.C Pai and P.K Rohatgi, J Mater Sci., 13, 329–335 (1978) P.K Rohatgi and B.C Pai, Wear, 59, 323–332 (1980) J Zhang, R.J Perez and E.J Lavernia, Acta Metall., 42, (2) 395–409 (1994) J.N Wei, H.F Cheng, Y.F Zhang, F.S Han, Z.C Zhou and J.P Shui, Mater Sci Eng., 325A, 444–453 (2002) [28] [29] [30] [31] [32] P.K Rohatgi, S Ray and Y Liu, Int Mater Rev., 37, (3) 129–149 (1992) H Hocheng, S.B Yen, T Ishihara and B.K Yen, Composites, 28A, 883–890 (1997) G.M.L Ted and C.Y.A Tsao, Compos Sci Technol., 60, 65–74 (2000) A.R Riahi and A.T Alpas, Wear, 251, 1396–1407 (2001) P Sharma, D Khanduja and S Sharma, J Mater Res Technol., 5, (1) 29–36 (2016) P.K Rohatgi, R Asthana and S Das, Int Met Rev., 31, (3) 115–139 (1986) W Ames and A.T Alpas, Metall Mater Trans A, 26A, 85–98 (1995) M Kestursatya, J.K Kim and P.K Rohatgi, Mater Sci Eng., 339A, 150–158 (2003) B.K Yen and T Ishihara, Wear, 198, 169–175 (1996) S Basavarajappa, G Chandramohan, A Mahadevan, M Thangavelu, R Subramanian and P Gopalakrishnan, Wear, 262, (7–8) 1007–1012 (2007) J.B Yang, C.B Lin, T.C Wang and H.Y Chu, Wear, 257, 941–952 (2004) A Baradeswaran and A.E Perumal, Composite: B, 56, 472–476 (2014) F Akhlaghi and A.Z Bidaki, Wear, 266, 37–45 (2009) Y.B Liu, S.C Lim, S Ray and P.K Rohatgi, Wear, 159, 201–205 (1992) M.K Surappa and P.K Rohatgi, Met Technol., 5, 358–361 (1978) H.T Son, T.S Kim, C Suryanarayana and B.S Chun, Mater Sci Eng A., 348, 163–169 (2003) C.B Lin, R.J Chang and W.P Weng, Wear, 217, 167–174 (1998) B.P Krishan, M.K Surappa and P.K Rohatgi, J Mater Sci., 16, 1209–1216 (1981) A.S.T.M, Standard E8, Standard Test Method for Tension Testing of Metallic Materials, ASTM, International, West Conshohocken (USA) (2004) P Sharma, S Sharma and D Khanduja, J Asian Ceram Soc., 3, (3) 352–359 (2015) A.M Hassan, G.M Tashtoush and A.K.J Ahmed, J Compos Mater., 41, 453–465 (2007) A Baradeswaran and A.E Perumal, Composites: B, 56, 464–471 (2014) S.N Prashant, N Madeva and V Auradi, Int J Metall Mater Sci Eng., 2, (3) 85–95 (2012) S Suresha and B.K Sridhara, Mater Des., 31, 4470–4477 (2010) J.U Ejiofor and R.G Reddy, J Miner Process., 49, 31–37 (1997) B.P Krishan and P.K Rohatgi, Meteorol Technol., 11, 41–44 (1984) Please cite this article in press as: P Sharma, et al., A study on wear behaviour of Al/6101/graphite composites, J Asian Ceram Soc (2017), http://dx.doi.org/10.1016/j.jascer.2016.12.007 ... Varying sliding distance (m/s) (c) Variation of wear rate with varying sliding distance at 1.2 m/s Fig 13 (a) Variation of wear rate with varying sliding distance at 0.4 m/s (b) variation of wear. .. tribological behaviour of AMCs Wear rate and coefficient of friction of all man- ufactured AMCs is better than that of cast metal matrix and both Wear rate and coefficient of friction reduces significantly... (1996) S Basavarajappa, G Chandramohan, A Mahadevan, M Thangavelu, R Subramanian and P Gopalakrishnan, Wear, 262, (7–8) 1007–1012 (2007) J.B Yang, C.B Lin, T.C Wang and H.Y Chu, Wear, 257, 941–952