Investigation on wear behavior of Al6061 hybrid metal matrix composite in braking applications
S. Rajesh, C. Velmurugan, P. S. Samuel Ratna Kumar
Department of Mechanical Engineering, Kumaraguru College of Technology, Coimbatore, India
*Corresponding Author Email: rajesh.s.mec@kct.ac.in, velmurugan.c.mec@kct.ac.in, samuelratnakumar.ps.mec@kct.ac.in
ABSTRACT:
The present article investigates the dry sliding wear behavior of Aluminium 6061 hybrid metal matrix composite (alhmmc) and compare the results with cast iron(ci). The (ALHMMC) possess light weight, low corrosion and high strength which offer unique property, which can use in automobile brakes. The main objective of this work to investigate the sliding wear behavior of al6061 composites reinforce mos2 particles and to optimize the process parameters in braking applications. the composite were prepared by using stir casting technique and optimization were done by using taguchi technique. The optimal combinations input parameters which will positively influence the wear rate and coefficient of friction. Dry sliding wear test method was used to conduct the experiments by using pin-on-disc wear testing machine. design of experiment was selected for analysis of the data. Investigation about applied load, sliding speed, sliding distance on wear rate and coefficient of friction during wearing process was carried out using ANOVA. results show that applied load has the highest influence followed by sliding distance and sliding velocity.
INTRODUCTION:
Aluminium alloys playing major role in the field of automobile application field like pistons, brake rotors and engine block cylinder liners. Wear resistance of material is combined with both optimum material strength (hardness) and toughness properties. The effect of type of reinforcements such as alumina, SiC particle and the outcome of this work clearly states that, particulate reinforcement results in improving the wear resistance of MMCs[1]. The MMCs fabrication technique plays a vital role in enhancing the tribological and mechanical properties, in this aspect the author had slightly modified the fabrication procedure as follows, materials placed in a graphite crucible and are heated in an inert atmosphere, then the molten metal undergone two step stirring action to maintain homogenous distribution of reinforcements [2].
From the comparison of performance characteristics of Al alloy reinforced with 5 wt% SiC fabricated through stir casting and powder metallurgy, it is a piece of evidence that the stir casting specimens have superior strength compared to powder metallurgy made specimens[3].that enhances their usage in automobile applications like brake drum, brake rotor, pistons and cylinder block [4]. In modern days, HMMCs are being produced by Al, Ti, Cu, Mg and their alloys principally reinforced with hard ceramic particles like alumina, silicon carbide[5]. S. Dhanasekaran reported the abrasive wear behavior of sintered steels prepared with MoS2 addition. In this study Abrasive wear tests were conducted by sliding against the SiC abrasive sheet at room temperature. It shows that MoS2 added material exhibited a high coefficient of friction and good wear resistance compared to the base composition compressive strength, hardness and density are influenced by the addition of MoS2[6]. QunjiXue have investigated the tribological properties of SiC whisker and molybdenum particle reinforced aluminum matrix composites under lubrication and revealed that the composites exhibited good friction- and wear-resistance properties. Results revival that with increasing load, the wear rate increases quickly [7]. S. Dharmalingam results shows the volume loss and frictional force are measured and the results used to evaluate the dry sliding performances are specific wear rate and coefficient of friction[8]. Aravind Vadiraj investigated the friction and wear behavior of MoS2, boric acid, graphite and TiO2 at four different sliding speeds (1.0, 1.5, 2.0, 2.5m/s) and compared with the dry sliding condition. The results show the friction coefficient reduces with increase in sliding speeds for all the conditions[9]. Wear is removal of material from a solid surface by the sliding action of another solid and is caused by friction, fatigue or vibration. The wear behavior of Aluminium reinforced alloy using pin-on disc type machine for wear properties measurement. By increasing reinforcement particle wear, toughness increases. [10]. Pin-on-Disc uses volumetric loss, and is evaluated from decrease in length of pin. Vaccari identified aluminum matrix composites as potential substitute of brake pad material[11]. The coefficient of friction decreased as the surface of the AMCs become rougher at higher load. This was considered due to removal of alumina particles from the surface of AMCs during wear test and the remaining aluminum alloy without alumina particles made the material softer[12]. Mathematical models were developed by many investigators for wear resistance of Al-SiC composites. They adopted design of Experiments (DOE)concept for conducting experiments. The method of least squares was used to calculate the regression coefficients and analysis of variance(ANOVA) technique was used to check the significance of the models was developed [13]. The coefficient of friction slightly decreases with increasing the % of reinforcements and micro hardness of the hybrid composite test specimens increases with increasing volume fraction of particulates reinforcement [14]. Dry sliding performances, the coefficient of friction for Al6061 alloy is influenced primarily by sliding distance followed by sliding speed and then applied load whereas in AlHMMC the friction coefficient is varied by applied load, sliding speed and at last by sliding distance[15].Applied load is only parameter which is largely influence the coefficient of friction in both composites. The density of Al 6063/ MoS2/ were increasing when reinforcement of MoS2 increases from 3% to 9%. The Ultimate Tensile Strength decreasing due to the additions of 3% to 9% of MoS2 .Investigation also predicts that hardness increases due to varying addition of MoS2[16,17].
EXPERMENTAL DETAILS:
Selection of matrix material:
This paper work matrix is Al6061 and a reinforcement material is MoS2. The chemical composition of the matrix material is as shown the Table 1
Table 1.Chemical composition of Al6061 (Weight %)
Mg |
Si |
Fe |
Cu |
Ti |
Cr |
Zn |
Mn |
Be |
V |
0.92 |
0.76 |
0.28 |
0.22 |
0.10 |
0.07 |
0.06 |
0.04 |
0.003 |
0.01 |
Selection of Reinforcement materials:
The chemical composition of MoS2 is shown in Table 2. It is a soft material with a hardness of 1-2 Mohr’s scale, with a melting point of 36500 C. In order to improve the consolidation of particles in the layer, external excitation of loading system has been used using pin-on-disk device. The present work shows that MoS2 particles have excellent anti-friction and wear resistance performances with high load carrying capacity.
Table 2.Chemical composition of MoS2(Weight%)
Fe |
Pb |
MoO3 |
SiO2 |
H2O |
KOH |
Oil |
0.3 |
0.2 |
0.2 |
0.20 |
0.20 |
0.50 |
0.50 |
Composite preparation:
Al 6061 alloy composite were fabricated using stir cast setup shown in Figure. Al6061 alloy was melted to the desired super heating temperature of 1063 in a crucible made from Mos2 placed inside the electric induction furnace. The stirring was continued to about five minutes at an average stirring speed of 300-350 rpm under protected organ gas, then finally MoS2 particles are poured uniformly distributed throughout the matrix alloy. At the end of stirring period the molten metal inside the crucible was taken outside the furnace and melt with reinforced particulates was poured into a dried, coated and permanent metallic preheated cylindrical mould of size 15 mm diameter and 100 mm length. The die was released after 6 hours and the cast specimens were taken out. Finally cast composite were machined in the form of cylinder 8 mm diameter and 30 mm length for conducting wear test.
Design of experiments:
Design of experiments (DOE) is a formal structured technique for studying any situation that involves a response that varies as a function of one or more independent variables. It is one of the important and powerful statistical techniques to study the effect of multiple variables simultaneously and involves a series of steps which must follow a certain sequence for the experiment to yield an improved understanding of process performance. Taguchi approach relies on the assignment of factors in specific orthogonal arrays to determine those test combinations. The aim of the experimental plan is to find the important factors and combination of factors influencing the wear process to achieve the minimum wear rate. The experiments relating the influence of sliding velocity, applied load and distance travelled.
Table 4 shows the experimental details of design factors and their levels for the wear test results. The results for various combinations of parameters were obtained by conducting the experiment as per the orthogonal array show in Table 3.
Applied load, sliding speed, and sliding distance and varying them for three levels. According to the rule that degree of freedom for an orthogonal array should be greater than or equal to sum of those wear parameters, a L27 Orthogonal array which has 27 rows and 3 columns was selected. Dry-sliding wear tests were conducted using a pin on a disc apparatus and the variations in wear rate of specimens with different applied loads, sliding velocity, distance travelled under dry sliding condition are given in Table 5.
Table 3. Parameters used for conducting the experiment
S.NO |
COLUMN 1 |
COLUMN 2 |
COLUMN 3 |
1 |
1 |
1 |
1 |
2 |
1 |
1 |
1 |
3 |
1 |
1 |
1 |
4 |
1 |
2 |
2 |
5 |
1 |
2 |
2 |
6 |
1 |
2 |
2 |
7 |
1 |
3 |
3 |
8 |
1 |
3 |
3 |
9 |
1 |
3 |
3 |
10 |
2 |
1 |
2 |
11 |
2 |
1 |
2 |
12 |
2 |
1 |
2 |
13 |
2 |
2 |
3 |
14 |
2 |
2 |
3 |
15 |
2 |
2 |
3 |
16 |
2 |
3 |
1 |
17 |
2 |
3 |
1 |
18 |
2 |
3 |
1 |
19 |
3 |
1 |
3 |
20 |
3 |
1 |
3 |
21 |
3 |
1 |
3 |
22 |
3 |
2 |
1 |
23 |
3 |
2 |
1 |
24 |
3 |
2 |
1 |
25 |
3 |
3 |
2 |
26 |
3 |
3 |
2 |
27 |
3 |
3 |
2 |
Table 4. Parameters used in the wear test
Level |
Sliding velocity(m/s) |
Sliding distance(m) |
Load(N) |
1 |
2 |
200 |
10 |
2 |
3 |
350 |
20 |
3 |
4 |
500 |
30 |
Table 5.Experimental results for wear test
Level |
Sliding Velocity (m/s) |
Sliding distance (m) |
Applied load (N) |
Wear Rate (x10-3 MM3/NMM) |
1 |
2 |
200 |
10 |
0.803 |
2 |
2 |
200 |
10 |
0.813 |
3 |
2 |
200 |
10 |
0.823 |
4 |
2 |
350 |
20 |
0.378 |
5 |
2 |
350 |
20 |
0.378 |
6 |
2 |
350 |
20 |
0.36 |
7 |
2 |
500 |
30 |
0.108 |
8 |
2 |
500 |
30 |
0.107 |
9 |
2 |
500 |
30 |
0.107 |
10 |
3 |
200 |
20 |
0.402 |
11 |
3 |
200 |
20 |
0.39 |
12 |
3 |
200 |
20 |
0.4 |
13 |
3 |
350 |
30 |
0.153 |
14 |
3 |
350 |
30 |
0.158 |
15 |
3 |
350 |
30 |
0.152 |
16 |
3 |
500 |
10 |
0.32 |
17 |
3 |
500 |
10 |
0.36 |
18 |
3 |
500 |
10 |
0.34 |
19 |
4 |
200 |
30 |
0.29 |
20 |
4 |
200 |
30 |
0.27 |
21 |
4 |
200 |
30 |
0.28 |
22 |
4 |
350 |
10 |
0.47 |
23 |
4 |
350 |
10 |
0.45 |
24 |
4 |
350 |
10 |
0.49 |
25 |
4 |
500 |
20 |
0.18 |
26 |
4 |
500 |
20 |
0.16 |
27 |
4 |
500 |
20 |
0.19 |
Fig .1: schematic view of pin on disc apparatus
RESULTS AND DISCUSSION:
Analysis of variance Results for wear test
The experimental results were analyzed with Analysis of Variance (ANOVA) which is used to investigate the influence of the considered wear parameters namely; applied load, sliding speed, and sliding distance that significantly affect the performance measures. By performing analysis of variance, it can be decided which independent factor dominates over the other and the percentage contribution of that particular independent variable. The results of Al6061 wear rate tormetal matrix composites reinforced with 10wt% MoS2 for three factors are varied and the interactions of those factors are shown in Table. This analysis is carried out for a significance level of α=0.05, i.e. for a confidence level of 92%. Sources with a P-value less than 0.05 were considered to have a statistically significant contribution to the performance measures.
Fig .2: Scanning Electron microscope Test Result
Table .6: Analysis of variance for wear rate
Source |
DF |
Adj SS |
Adj MS |
F-value |
P-value |
Contribution % |
Sliding velocity |
1 |
0.06625 |
0.066248 |
22.76 |
0.000 |
6.08 |
Sliding Distance |
0.37440 |
0.374401 |
128.61 |
0.000 |
34.3 |
|
Load |
1 |
0.58356 |
0.583560 |
200.46 |
0.000 |
53.5 |
Error |
23 |
0.06696 |
0.002911 |
- |
- |
6.12 |
Total |
26 |
1.09116 |
- |
- |
- |
100.0 |
Multiple Linear Regression Model:
A multiple linear regression model is developed using statistical software “MINITAB 15”. The predicted wear rate found using multiple linear regression model is shown in Table 8. The regression equation developed for Al6061 and 10wt% MoS2 MMCs wear rate as follows.
Wr = 1.22 – 0.0606 V - 0.000959 D - 0.0180 P
Table.7: Shows the wear rate of composite materials.
Level |
Sliding Velocity (m/s) |
Sliding distance (m) |
Applied load (N) |
Wear Rate (x10-3 MM3/NMM) |
Predicted wear rate |
1 |
2 |
200 |
10 |
0.803 |
0.727 |
2 |
2 |
200 |
10 |
0.813 |
0.727 |
3 |
2 |
200 |
10 |
0.823 |
0.727 |
4 |
2 |
350 |
20 |
0.378 |
0.403 |
5 |
2 |
350 |
20 |
0.378 |
0.403 |
6 |
2 |
350 |
20 |
0.36 |
0.403 |
7 |
2 |
500 |
30 |
0.108 |
0.092 |
8 |
2 |
500 |
30 |
0.107 |
0.092 |
9 |
2 |
500 |
30 |
0.107 |
0.092 |
10 |
3 |
200 |
20 |
0.402 |
0.489 |
11 |
3 |
200 |
20 |
0.39 |
0.489 |
12 |
3 |
200 |
20 |
0.4 |
0.489 |
13 |
3 |
350 |
30 |
0.153 |
0.165 |
14 |
3 |
350 |
30 |
0.158 |
0.165 |
15 |
3 |
350 |
30 |
0.152 |
0.165 |
16 |
3 |
500 |
10 |
0.32 |
0.378 |
17 |
3 |
500 |
10 |
0.36 |
0.378 |
18 |
3 |
500 |
10 |
0.34 |
0.378 |
19 |
4 |
200 |
30 |
0.29 |
0.246 |
20 |
4 |
200 |
30 |
0.27 |
0.246 |
21 |
4 |
200 |
30 |
0.28 |
0.246 |
22 |
4 |
350 |
10 |
0.47 |
0.462 |
23 |
4 |
350 |
10 |
0.45 |
0.462 |
24 |
4 |
350 |
10 |
0.49 |
0.462 |
25 |
4 |
500 |
20 |
0.18 |
0.138 |
26 |
4 |
500 |
20 |
0.16 |
0.138 |
27 |
4 |
500 |
20 |
0.19 |
0.138 |
Effect of applied load and sliding speed on specific wear rate of AlHMMC:
From the Fig.3 it can be observed that the specific wear rate of Al6061 HMMC is retained almost same even at maximum sliding speed and at minimum applied load. This behaviour is obtained may be due to the formation of oxide layers between the mating surfaces. At high sliding speeds there will not be that much contact between pin and the disc this in due course results in less specific wear rate. At maximum loads this oxide layer was broken and that leads to huge wear in the pin of Al6061 HMMC.
Figure 3: Discrepancy of Specific Wear Rate with Sliding distance, sliding speed and applied load for AlHMMC.
Effect of applied load and sliding speed on coefficient of friction of AlHMMC:
Coefficient of friction the phenomena is required to achieve any objective. At higher speeds, due to high friction on the surfaces there is a chance for tribo layer formation between contacting surfaces. If the coefficient of friction is less than the chance of slippage will be high. In order to avoid these two extreme end conditions it‟s necessary to maintain moderate stable coefficient of friction throughout. Stable frictional coefficient at high speed and load is achieved for AlHMMC
Figure 4: Discrepancy of Co-Efficient of Friction with Sliding Distance, Sliding Speed and Applied Load for AlHMMC
At higher speeds, due to high friction on the surfaces there is a chance for tribo layer formation between contacting surfaces [6 [18].From Fig.5 and 6, it can be seen that the specific wear rate of AlHMMC is very less even at maximum sliding speed and at minimum applied load. This behaviour is obtained may be due to the formation of tribo layer between contact surfaces. At high sliding speeds this layer will be formed and it acts as a protective layer between pin and the rotating disc. As a result specific wear rate at higher speeds and higher distances will be less compared to all other working parametric conditions for AlHMMC‟s.
METHODOLOGY:
The following are the basic steps need to be carried in the current project.
CONCLUSIONS:
• The experimental result shows that as percentage of MoS2 increases the wear rate decreases.
• Based on Taguchi L27 Orthogonal Array wear test experiments were conducted successfully and calculated wear rate was substituted in MINITAB 17 and analyzed the effect of each parameter on wear rate.
• From response table signal to noise ratio for smaller is the better option, it was found that Load is affecting more on wear rate.
• Design of experiments by Taguchi method was successfully used to optimize the tribological behaviour of Al6061-MoS2 composites
REFERENCES:
1. A. Megalingam and V. Baskaran (2014).Dry Sliding Tribological Characterization and Parameters Optimization of Aluminium Hybrid Metal Matrix Composite for Automobile Brake Rotor Applications M. Kumar, International Conference on Advances in Design and Manufacturing pp368-373.
2. Jasmi Hashim, (2001) “The Production of cast Metal matrix composite by a modified stir casting method”, Journal Technology, Vol. 35, Pp. 9-20.
3. Jayaseelan, V., Kalaichelvan, K., Kannan, M., Vijay Ananth, S. (2010). “Extrusion characterizes of Al/Sic by different manufacturing process”, Internal Journal of Applied Engineering Research, Vol.1, Pp.194-199,
4. Prasad, S.V., and Asthana, R, (2004)“Aluminium-Metal Matrix Composites for Automotive Applications: Tribological Considerations”, Tribological Letters, Vol.17, Pp. 445–453.
5. Ashok Kr. Mishra, Rakesh Sheokand, Dr. R K Srivastava(2012) Tribological Behaviour of Al-6061/SiC Metal Matrix Composite by Taguchi’s Techniques International Journal of Scientific and Research Publications, Volume 2, Issue 10,
6. Dhanasekaran. S, Gnanamoorthy.(2007) R. Abrasive wear behavior of sintered steels prepared with MoS2 addition. Where: 617–623.
7. Velmurugan, C. Subramanian, R. et al.(2012) “Experimental study on the effect of SiC and graphite particles on weight loss of Al 6061 hybrid composite materials”, Journal of Tribology and Surface Engineering, 2011, vol. 2, pp.49-68.
8. Aravind Vadiraj, Kamaraj. M and Sreenivasan. V. S. Effect of solid lubricants on friction and wear behavior of alloyed gray cast iron. Indian Academy of Sciences: 37: 569-577.
9. M. J. Neale, ed., 1973. Tribology Handbook.
10. Ashok Kr. Mishra, Rakesh Sheokand, Dr. R K Srivastava (2012)Tribological Behaviour of Al-6061/SiC Metal Matrix Composite by Taguchi’s Techniques International Journal of Scientific and Research Publications, Volume 2, Issue 10.
11. FaizAhmada, S.H. Jason Lob, Muhammad Aslama and Ahmad Haziqa( 2013),‘Tribology Behaviour of Alumina Particles Reinforced Aluminium Matrix Composites and Brake Disc Materials’, Procedia Engineering, vol. 68, pp 668-674.
12. Madeva Nagaral, Shivananda B K, Shambhuling V S, V Auradi” wear behaviour of sic reinforced al6061 alloy metal matrix composites by using taguchi’ stechniques., International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308 pp. 800-804.
13. Rehman, A., Das, S., Dixit, G.,(2010) “Analysis of stir die cast Al–SiC composite brake drums based on coefficient of friction”, Tribology International, Vol. 51, Pp.36-41,
14. Mitesh Kumar, Ashok Kumar Mishra Mechanical Behavior of Al 6063/ Mos2/ Al2o3Hybrid Metal Matrix Composites International Journal of Scientific and Research Publications, Volume 4, Issue 12, December
15. Winer. W. O. Molybdenum Disulphide as a Lubricant: A Kevie of the Fundamental Knowledge. Wear 1966: 422–452.
16. Velmurugan, C., Subramanian, R., Thirugnanam, S. Anandavel, B.(2013) "Investigation of friction and wear behavior of hybrid aluminium composites", Industrial Lubrication and Tribology, (2012),Vol. 64 pp. 152 – 163.
17. Uvaraja, V. C., Natarajan, N., Rajendran, I., Sivakumar K., “Tribological Behavior of Novel Hybrid Composite Materials Using Taguchi Technique. Journal of Tribology”, Vol.135, Pp.021101-12.
18. Basavarajappa, S., Chandran Mohan, G., Mukund, K., Ashwin, M., and Prabu, M.(2006), “Dry Sliding Wear Behaviour of Al2219/Sic/Gr Hybrid Metal Matrix Composites,” Journal of Materials Engineering and Performance, Vol.15, Pp. 668–674.
Received on 09.08.2017 Accepted on 09.10.2017
©A&V Publications all right reserved
Research J. Engineering and Tech. 2017; 8(4): 383-388.
DOI: 10.5958/2321-581X.2017.00068.X