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NbC nano composite using Taguchi technique
Materials Today: Proceedings xxx (xxxx) xxx
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Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique T.S. Sachit a,⇑, N. Mohan b, R. Suresh c, M. Akshay Prasad d a
Department of Mechanical Engineering/Symbiosis Institute of Technology/Symbiosis International (Deemed University), Pune 411057, India Department of Industrial Engineering and Management/Dr. Ambedkar Institute of Technology, Bengaluru 560056, India c Department of Mechanical and Manufacturing Engineering, M.S. Ramaiah University of Applied Sciences, Bengaluru, India d Department of Mechanical Engineering, RNS Institute of Technology, Bengaluru, India b
a r t i c l e
i n f o
Article history: Received 5 August 2019 Accepted 12 September 2019 Available online xxxx Keywords: Pin-on-disc Dry sliding wear Powder metallurgy ANOVA Scanning electron microscopy Tantalum niobium carbide
a b s t r a c t Dry sliding wear behavior of aluminum LM4 based composite reinforced with Tantalum niobium carbide ceramic powder by varying percentage of reinforcement as 0.5 wt% to 2 wt%. Powder metallurgy method was used to develop the composites. Pin-on-disc apparatus was used to evaluate the dry sliding wear behavior of the developed composites. Taguchi design of experiment was used to optimization. The influence of various parameters are investigated by analysis of variance (ANOVA). From the wear results, it was observed that the applied load is having more influence on dry sliding wear followed by sliding speed. Also it was observed that percentage of reinforcement of (Tantalum Niobium carbide) Ta/NbC shows some influence on dry sliding wear rate. The worn surface analysis was done by using scanning electron microscopy (SEM). The analysis shows that incorporation of hard ceramic composites in alloys plays a major role in dry sliding wear resistance properties. Ó 2019 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International conference on Materials and Manufacturing Methods.
1. Introduction Aluminum alloy based composites gaining more focus in automotive and aerospace industries because of its admirable properties like light weight, high strength along with good thermal properties [1–3]. These composites replacing the conventional aluminum alloys in wide range of applications. Recent development in aluminum based composites makes more beneficial and necessary in the field of automotive and space applications. Incorporation of nano reinforcement in the aluminum alloy is one of the major development in composite research. Good strength even at Low volume fraction is one of the key to success in the nano composites [4]. Composites are manufactured using different conventional techniques like solid state fabrication and liquid state fabrication. Among different fabrication processes, powder metallurgy (P/M) method is one of the most beneficial method to achieve good dimensional accuracy of final product and uniform distribution of reinforcing particles [5]. Several type of reinforcing particles are used to fabricate the composites depending upon the area of application. Ceramic particles possess higher stability and rigidity ⇑ Corresponding author. E-mail address: [email protected] (T.S. Sachit).
which are used as reinforcement particles in some particular applications. Reinforcement of hard cermet carbide particles into the aluminum alloy improves the mechanical and tribological properties in both at room and elevated temperature along with higher hardness [6–7]. Lot of researchers attempted to understand the mechanical and tribological characteristics of AMCs developed by different fabrication techniques. Different reinforcing particles are utilized during fabrication and testing of AMCs. Basavarajappa et al. [8] studied importance of reinforcement particle in enhancing wear behavior of Al2219-SiC AMCs. Panwar et al. [9] investigated on wear performance of LM13-Zircon sand at elevated temperature. Reported that hardness and wear resistance improved by the addition of hard particles. LM4 aluminum alloy provides high mechanical strength and better wear resistance property compare to other aluminum alloys [10]. Tantalum Niobium Carbide (Ta/ NbC) is one of the new age of ceramic particles. Tantalum which is used in the production of electric components. Also used in surgical implants, it can replace bone. It is very resistant to corrosion so that these ceramics used for turbine blades. Niobium carbide are having high hardness, high melting point which provides good thermal resistance [11]. N.Mohan et al. [12] studied abrasive wear behavior of glass fabric epoxy hybrid composites filled with hard powders. Results revealed that increase in abrading distance
https://doi.org/10.1016/j.matpr.2019.09.043 2214-7853/Ó 2019 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International conference on Materials and Manufacturing Methods.
Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043
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T.S. Sachit et al. / Materials Today: Proceedings xxx (xxxx) xxx
increases the wear volume loss. Also observed that the composites with hard powder filled specimens shows less specific wear rate when compared with unfilled specimens. Radhika et al. [13] reported the importance of Taguchi technique in optimizing the number of trails compared with design of experiments. Also reported the possibility of finding the interaction between the factors. Current research work aims in understanding the dry sliding wear behavior of aluminum LM4 reinforced with tantalum niobium carbide hard nano particles. The influence of applied load, percentage of reinforcement and sliding speed on wear behavior of developed composites are analyzed using Taguchi method. The most influencing test parameter of dry sliding wear on developed composites was identified and reported.
sure of 160 MPa using hydraulic pressing machine holding time was maintained for 10 s. After cold pressing the green compacts of size 12 mm dia and 18 mm height were removed from die and ready for sintering process [16–18]. The green compacts were sintered at 5600C for one hour in a tubular vacuum furnace under argon gas atmosphere. After sintering all sintered specimens are kept cool for 3 h in the furnace itself. Similar procedure was followed to fabricate specimens of 0.5 wt% LM4 + Ta/NbC to 2 wt% LM4 + Ta/NbC. Fig. 1 shows the steps involved in powder metallurgy process. Fig. 2a shows the process of powder compaction using hydraulic press and Fig. 2b shows the images of developed specimens for wear test.
2. Experimental work 2.1. Materials and method The metal matrix nano composite are developed by considering aluminum LM4 as a matrix material. The chemical composition is shown in Table 1. The commercially available Tantalum niobium carbide (Ta/NbC) in the ratio of 60:40 is used as reinforcement material (As received average particle size of 150-200Nm and density of Ta/NbC is 10.8 gm/cc). The amount of Ta/NbC reinforcement varies from 0.5, 1, 1.5 and 2 wt%. The composites are developed through powder metallurgy technique (see Table 2). A weighed quantity of Aluminum LM4 powder of average particle size of 50 µm was first milled in a planetary ball mill for about 3 h to reduce the particle size. The ball to powder ratio was maintained at 25:1 in order to achieve uniformity throughout the powder particles [14–15]. A weighed quantity of Ta/NbC powder was pre heated to a temperature of 3000C to remove the oxidation of the powder particles. The pre heated Ta/NbC powder then mixed with milled aluminum LM4 alloy powder and milled for 15 min in order to get proper mixing of matrix and reinforcement particles. 2 wt% of Poly vinyl Alcohol (PVA) solution added to the mixed powder for proper bonding between the powder particles. Zinc stearate solution was applied throughout the die wall for proper lubrication and easy of ejection [20]. The mixed composite powders were then cold compacted in a hardened steel die at a pres-
Fig. 2a. Hydraulic press with compaction die.
Table 1 Chemical composition of matrix material Aluminum LM4. Elements
Si
Cu
Mn
Mg
Ni
Al
Wt%
6
3
0.4
0.2
0.3
bal
Table 2 List of factors and levels for wear test. Factors
Level 1
Level 2
Level 3
Level 4
Load (L) in N Sliding speed (S) in rpm Wt% of Ta/NbC (R)
10 200 0.5
20 400 1
30 600 1.5
40 800 2
Fig. 1. Steps involved in Powder metallurgy process.
Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043
T.S. Sachit et al. / Materials Today: Proceedings xxx (xxxx) xxx
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The formula used to calculate dry sliding wear rate was given below.
Wr ¼ DW=t gram=min
ð1Þ
A fixed sliding diameter of 100 mm was set for all the test runs. The wear parameters selected for the wear test are load, speed and weight percentage. The influence of some process parameters on dry sliding wear behaviour of aluminum matrix composites are well understood by taguchi technique [16]. Based on the number of factors and their levels L16 orthogonal array was selected for optimization. The experimental results are converted into a signal-to-noise (S/N) ratio. ‘‘Smaller is better” characteristic was taken for investigation of optimum wear rate of developed AMCs. The S/N ratio was calculated by using following Eq. (2).
S N ¼ 10log 1=nðy1 þ y2 þ þ ynÞ
ð2Þ
where, y1, y2 are the response values and n is the number of trials. ANOVA was used to identify the most influencing factor. The mean response table and S/N response tables are drawn from the mini tab software. The percentage of contribution of each individual factors are estimated by using ANOVA table. 3. Results and discussion 3.1. SEM analysis
Fig. 2b. Wear test specimen.
2.2. Experimental techniques 2.2.1. Microstructure examination The microscopic examination was carried out on powder samples and developed composites. The sintered samples were polished using emery papers of grit size 600 and 800. They were then polished using diamond paste using double disc polisher. The polished specimens etched with Keller’s reagent.
2.2.2. Dry sliding wear examination Dry sliding wear behavior of developed composite specimens are examined as per ASTM G99 standard [14]. The surface of the specimen was first cleaned with acetone in order to remove the contaminants. The wear rate was estimated by means of weight loss of the specimen per minute. Weight loss of the specimen was calculated by taking difference between the initial and final weight of the specimen. The specimen weight was recorded using electronic weight balancing machine of accuracy of 0.1 mg [15,21].
Fig. 3 shows the SEM images of LM4-Ta/NbC composites contain 1 wt% and 2 wt% of reinforcement. The uniform distribution of reinforcement were seen from the SEM images. Powder metallurgy method ensures the homogeneous distribution of Ta/NbC particles in the composite. Fig. 4 shows the microscopic images of the LM42 wt%Ta/NbC composites. 3.2. Taguchi design for wear rate optimization Wear rate experiments were carried out based on 4 level 3 factor orthogonal array L16. The results of wear rate based on Taguchi design was provided in Table 3. The experiment consist of 16 tests each test consist of different process parameters. The weight loss obtained due to dry sliding wear of aluminum LM4-Ta/NbC composites consisting of different weight percentage. Table 3 shows the wear test results. Figs. 5 and 6 shows the S/N ratio response table and mean response table respectively [19]. The highest response in the S/N ratio plot gives the optimum wear rate results. Fig. 6 shows the variation of mean value with the changes in control factors on the weight loss can be observed.
Fig. 3. SEM images of LM4-Ta/NbC composites.
Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043
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Fig. 4. Microscopic images of LM4-Ta/NbC composites.
Table 3 Experimental results using L16 orthogonal array. Sl No
Load (L) in N
Sliding speed (S) in rpm
Wt% of Ta/NbC (R)
Wear rate (Wr gm/min 103)
S/N ratio for wear rate (dB)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
10 10 10 10 20 20 20 20 30 30 30 30 40 40 40 40
200 400 600 800 200 400 600 800 200 400 600 800 200 400 600 800
0.5 1 1.5 2 1 0.5 2 1.5 1.5 2 0.5 1 2 1.5 1 0.5
0.2468 0.2532 0.2586 0.2662 0.2675 0.2892 0.2722 0.2822 0.2865 0.2675 0.3021 0.3134 0.2846 0.3008 0.3142 0.3371
12.15 11.93 11.75 11.50 11.45 10.78 11.30 10.99 10.86 11.45 10.40 10.08 10.92 10.43 10.06 9.44
Fig. 5. Main effect plot for S/N ratios.
Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043
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Fig. 6. Main effect plot for means.
‘‘Smaller is better” parameter was selected to identify the optimum wear characteristic of each process parameter. From the table it was observed that applied load has high influence on wear rate. As the applied load increases the wear rate increases. Also Sliding speed increases wear rate increases gradually and as weight percentage increase the wear rate decreases. The delta value was used to identify the most influencing parameters. From the S/N response Tables 4 and 5 it can be observed that the the optimum wear rate was observed at 1th level of applied load, 1st level of sliding speed and 4th level of wt % of reinforcement. The ranking of the parameters are based on the S/N response tables. Table 6 shows the ANOVA results of the tested specimens. From the ANOVA table it can be noticed that, applied load has the greater influence (65.74%) apart from the applied load sliding speed (19.74%) also having influence on wear rate and wt % of Ta/NbC (10.36%) less influence on wear rate. The level of significance of 0.05 and confidence level of 95% selected for the current investiga-
Table 4 S/N ratio response table. Level
Load (L) in N
Sliding speed (S) in rpm
Wt% of Ta/NbC (R)
1 2 3 4 Delta Rank
11.83 11.13 10.7 10.21 1.62 1
11.34 11.15 10.88 10.5 0.84 2
10.69 10.88 11.01 11.29 0.6 3
tion. The R2 value obtained was 95.83% which was within the confidence level. 3.3. Estimation of optimum response parameters of wear rate Optimization of response carried out by selecting the optimum values in the mean response table.
lWR ¼ L1 þ S1 þ R4 2 T
ð3Þ
where, T = overall mean of wear rate = 0.2839 103 gm/min
L1 ,S1 &R4 = optimum wear rate values obtained from Table 5.
L1
= 0.2562 103 gm/min
S1 = 0.2713 103 gm/min
R4 = 0.2726 103 gm/min lWR = (0.2562 103 + 0.2713 103 + 0.2726 103) 2 0.2839 103 lWR = 0.2323 103 gm/min The confidence level and the significant populations are calculated by using Eqs. (4) and (5).
CICE
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 1 1 ¼ F a ð1; f e ÞV e þ neff R
CIpop
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi F a ð1; f e ÞV e ¼ neff
ð4Þ
ð5Þ
where, F a ð1; f e Þ = The F ratio
Table 5 S/N ratio response table for means. Level
Load (L) in N
Sliding speed (S) in rpm
Wt% of Ta/NbC (R)
1 2 3 4 Delta Rank
0.2562 0.2778 0.2924 0.3092 0.053 1
0.2713 0.2777 0.2868 0.2997 0.0284 2
0.2938 0.2871 0.282 0.2726 0.0212 3
neff ¼
N 1 þ ðDOF associated in the estimate of mean responseÞ
neff = 16/(1 + 9) = 1.6 N = number of experiments = 16 R = 3 (Number of trials) Ve is the error variance = 6.4 105 (From ANOVA table)
Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043
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Table 6 Analysis of Variance for S/N ratio for wear rate. Source
DF
Seq SS
Adj SS
Adj MS
F-value
P-Value
p%
Load speed Ta/NbC wt% Error Total
3 3 3 6 15 S = 0.00800217
0.006062 0.00182 0.000955 0.000384 0.009221
0.006062 0.00182 0.000955 0.000384
0.002021 0.000607 0.000318 0.000064
31.55 9.47 4.97
0 0.011 0.046
65.74 19.74 10.36 4.17
R-Sq = 95.83%
F a ð1; f e Þ = 5.9874 (for 95% confidence level and 0.05 significant level from F chart) The calculated CICE = 0.019 andCIpop = 0.015 CI for Confirmation experiment: Mean lWR -CICE < lWR < Mean lWR + CICE 0.2133 103 gm/min < lWR < 0.2513 103 gm/min The 95% CI for population is: Mean lWR -CIpop < lWR < MeanlWR + CIpop 0.2173 103 gm/min
R-Sq(adj) = 89.58%
4. Analysis of wear mechanism The wear mechanism of worn out surfaces was influenced by varying factors. Increase in the applied load, increases the frictional force between the pin and disc material and makes the delamination on the pin material. The SEM images of the worn surface and debris formed during high load and higher shear force are shown in Fig. 7(a–d). Finer debris were formed during low load condition due to lower friction between the surfaces. During initial condition the increase in the sliding speed gradually increases the wear rate at certain point of contact the thermal softening of the pin material influences more rate of wear during high sliding speeds. Due to thermal softening higher delamination and peeling of material particles took place from the surface of the pin material. But in some cases the increase in the sliding speed decreases the wear rate. The
Table 7 Confirmation experiment results along with predicted values. Response
Combination of Process variables (optimal)
Predicted optimal value
Predicted confidence interval at 95% confidence level
Confirmation experiment value
Wear rate
L1S1R4
0.2323 103 gm/min
0.2133 103 gm/min < lWR < 0.2513 103 gm/min 0.2173 103 gm/min < lWR < 0.2473 103 gm/min
0.2569 103 gm/min
Fig. 7. (a–d): The SEM images of the worn surface and debris formed during high load.
Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043
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reason behind this was due to continuous rubbing of the pin surface the asperities on the pin surface will become flat and results in adhesive type of wear mechanism. 5. Conclusion The following conclusions were drawn from the present research investigation; The LM4-Ta/NbC composites are produced by using powder metallurgy technique. The SEM images of the composite shows the uniform distribution of Ta/NbC particles and ensures that powder metallurgy is one of the effective method to fabricate composites. Taguchi method is used to optimize the process parameters and were identified for minimum wear rate are; Load 10 N, sliding speed = 200 rpm and wt% of Ta/NbC reinforcement = 2 wt%. From ANOVA results it is confirmed that applied load (65.74%), Sliding speed (19.74%) and Ta/NbC reinforcement (10.36%) influence on wear rate.
References [1] A. Vencl, Tribology of the Al–Si alloy based MMCs and their application in automotive industry, in: L. Magagnin (Ed.), Engineered metal matrix composites: forming methods, material properties and industrial applications, Nova Science Publishers, New York, 2012, pp. 127–166. [2] B. Stojanovic, J. Glisovic, Automotive engine materials, in: S. Hashmi (Ed.), Reference module in materials science and materials engineering, Elsevier, Oxford, 2016, pp. 1–9. [3] B. Stojanovic, M. Babic, S. Mitrovic, A. Vencl, N. Miloradovic, M. Pantic, Tribological characteristics of aluminium hybrid composites reinforced with silicon carbide and graphite, A Rev. J Balkan Tribol Assoc 19 (1) (2013) 83–96. [4] G. Cao, H. Konishi, X. Li, Mechanical properties and microstructure of Mg/SiC nanocomposites fabricated by ultrasonic cavitations based nanomanufacturing, J. Manufact. Sci. Eng. 130 (2008). [5] K.J. Joshua, S.J. Vijay, D.P. Selvaraj, Effect of nano TiO2 particles on microhardness and microstructural behavior of AA7068 metal matrix composites, Ceramics Int. 44 (17) (2018) 20774–20781.
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[6] O.M. Patil, N.N. Khedkar, T.S. Sachit, T.P. Singh, A review on effect of powder metallurgy process on mechanical and tribological properties of Hybrid nano composites, Mater. Today: Proc. 5 (2) (2018) 5802–5808. [7] T.S. Sachit, M.A. Khan, Effect of Particle Size on Mechanical and Tribological Behavior of LM4/SiCp Based MMC, Mater. Today: Proc. 5 (2) (2018) 5901– 5907. [8] S. Basavarajappa, G. Chandramohan, K. Mukund, M. Ashwin, M. Prabu, Dry sliding wear behavior of Al 2219/SiCp-Gr hybrid metal matrix composites, J. Mater. Eng. Perform. 15 (6) (2006) 668. [9] R.S. Panwar, O.P. Pandey, Study of wear behavior of zircon sand-reinforced LM13 alloy composites at elevated temperatures, J. Mater. Eng. Perform. 22 (6) (2013) 1765–1775. [10] S. Arivukkarasan, V. Dhanalakshmi, B. Stalin, M. Ravichandran, Mechanical and tribological behaviour of tungsten carbide reinforced aluminum LM4 matrix composites, Particul. Sci. Technol. 36 (8) (2018) 967–973. [11] M.G.D.V. Cuppari, S.F. Santos, Physical properties of the NbC carbide, Metals 6 (10) (2016) 250. [12] N. Mohan, S. Natarajan, S.P. KumareshBabu, Abrasive wear behaviour of hard powders filled glass fabric–epoxy hybrid composites, Mater. Des. 32 (3) (2011) 1704–1709. [13] N. Radhika, R. Raghu, Parametric study of dry sliding wear behavior of functionally graded Al LM25/Si3N4 composite by response surface methodology, Adv. Compo. Lett. 24 (6) (2015) 130–136. [14] G. Taguchi, S. Konishi, Taguchi methods, orthogonal arrays and linear graphs, tools for quality engineering, American Supplier Institute, 1987, pp. 35–38. [15] G. Lutjering, Property optimization through microstructural control in titanium and aluminum alloys, Mater. Sci. Eng. A 263 (1999) 117–126. [16] T.S. Sachit, M. Nagaraj, A. Bongale, N. Khedkar, Synthesis and mechanical characterization of aluminum-based hybrid nanocomposites reinforced with nano tungsten carbide and nano tantalum niobium carbide particles, Int. J. Mater. Eng. Innovat. 9 (4) (2018) 279–290. [17] J. Kumar, S. Punnose, C.K. Mukhopadhyay, T. Jayakumar, V. Kumar, Acoustic emission during tensile deformation of smoot hand notched specimens of near alpha titanium alloy, Res. Nondestruct. Evaluat. 23 (2012) 17–31. [18] T.S. Sachit, N. Mohan, Aluminum based hybrid nano composites: a review on reinforcement, mechanical and tribological characteristics, Int. J. of Adv. Res. 4 (11) (2016) 167–175, ISSN 2320-5407. [19] B.A. Kumar, N. Murugan, I. Dinaharan, Dry sliding wear behavior of stir cast AA6061-T6/AlNp composite, Trans. Nonferrous. Met. Soc. China. 24 (2014) 2785–2795. [20] T.S. Sachit, R.V. Nandish, Thermal analysis of Cr2O3 coated diesel engine piston using FEA, Mater. Today: Proc. 5 (2) (2018) 5074–5081. [21] T.S. Sachit, N. Mohan, Wear rate optimization of tungsten carbide (WC) nano particles reinforced aluminum LM4 alloy composites using Taguchi techniques, Mater. Res. Exp. 6 (6) (2019) 066564.
Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043
Contents lists available at ScienceDirect
Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr
Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique T.S. Sachit a,⇑, N. Mohan b, R. Suresh c, M. Akshay Prasad d a
Department of Mechanical Engineering/Symbiosis Institute of Technology/Symbiosis International (Deemed University), Pune 411057, India Department of Industrial Engineering and Management/Dr. Ambedkar Institute of Technology, Bengaluru 560056, India c Department of Mechanical and Manufacturing Engineering, M.S. Ramaiah University of Applied Sciences, Bengaluru, India d Department of Mechanical Engineering, RNS Institute of Technology, Bengaluru, India b
a r t i c l e
i n f o
Article history: Received 5 August 2019 Accepted 12 September 2019 Available online xxxx Keywords: Pin-on-disc Dry sliding wear Powder metallurgy ANOVA Scanning electron microscopy Tantalum niobium carbide
a b s t r a c t Dry sliding wear behavior of aluminum LM4 based composite reinforced with Tantalum niobium carbide ceramic powder by varying percentage of reinforcement as 0.5 wt% to 2 wt%. Powder metallurgy method was used to develop the composites. Pin-on-disc apparatus was used to evaluate the dry sliding wear behavior of the developed composites. Taguchi design of experiment was used to optimization. The influence of various parameters are investigated by analysis of variance (ANOVA). From the wear results, it was observed that the applied load is having more influence on dry sliding wear followed by sliding speed. Also it was observed that percentage of reinforcement of (Tantalum Niobium carbide) Ta/NbC shows some influence on dry sliding wear rate. The worn surface analysis was done by using scanning electron microscopy (SEM). The analysis shows that incorporation of hard ceramic composites in alloys plays a major role in dry sliding wear resistance properties. Ó 2019 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International conference on Materials and Manufacturing Methods.
1. Introduction Aluminum alloy based composites gaining more focus in automotive and aerospace industries because of its admirable properties like light weight, high strength along with good thermal properties [1–3]. These composites replacing the conventional aluminum alloys in wide range of applications. Recent development in aluminum based composites makes more beneficial and necessary in the field of automotive and space applications. Incorporation of nano reinforcement in the aluminum alloy is one of the major development in composite research. Good strength even at Low volume fraction is one of the key to success in the nano composites [4]. Composites are manufactured using different conventional techniques like solid state fabrication and liquid state fabrication. Among different fabrication processes, powder metallurgy (P/M) method is one of the most beneficial method to achieve good dimensional accuracy of final product and uniform distribution of reinforcing particles [5]. Several type of reinforcing particles are used to fabricate the composites depending upon the area of application. Ceramic particles possess higher stability and rigidity ⇑ Corresponding author. E-mail address: [email protected] (T.S. Sachit).
which are used as reinforcement particles in some particular applications. Reinforcement of hard cermet carbide particles into the aluminum alloy improves the mechanical and tribological properties in both at room and elevated temperature along with higher hardness [6–7]. Lot of researchers attempted to understand the mechanical and tribological characteristics of AMCs developed by different fabrication techniques. Different reinforcing particles are utilized during fabrication and testing of AMCs. Basavarajappa et al. [8] studied importance of reinforcement particle in enhancing wear behavior of Al2219-SiC AMCs. Panwar et al. [9] investigated on wear performance of LM13-Zircon sand at elevated temperature. Reported that hardness and wear resistance improved by the addition of hard particles. LM4 aluminum alloy provides high mechanical strength and better wear resistance property compare to other aluminum alloys [10]. Tantalum Niobium Carbide (Ta/ NbC) is one of the new age of ceramic particles. Tantalum which is used in the production of electric components. Also used in surgical implants, it can replace bone. It is very resistant to corrosion so that these ceramics used for turbine blades. Niobium carbide are having high hardness, high melting point which provides good thermal resistance [11]. N.Mohan et al. [12] studied abrasive wear behavior of glass fabric epoxy hybrid composites filled with hard powders. Results revealed that increase in abrading distance
https://doi.org/10.1016/j.matpr.2019.09.043 2214-7853/Ó 2019 2019 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the International conference on Materials and Manufacturing Methods.
Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043
2
T.S. Sachit et al. / Materials Today: Proceedings xxx (xxxx) xxx
increases the wear volume loss. Also observed that the composites with hard powder filled specimens shows less specific wear rate when compared with unfilled specimens. Radhika et al. [13] reported the importance of Taguchi technique in optimizing the number of trails compared with design of experiments. Also reported the possibility of finding the interaction between the factors. Current research work aims in understanding the dry sliding wear behavior of aluminum LM4 reinforced with tantalum niobium carbide hard nano particles. The influence of applied load, percentage of reinforcement and sliding speed on wear behavior of developed composites are analyzed using Taguchi method. The most influencing test parameter of dry sliding wear on developed composites was identified and reported.
sure of 160 MPa using hydraulic pressing machine holding time was maintained for 10 s. After cold pressing the green compacts of size 12 mm dia and 18 mm height were removed from die and ready for sintering process [16–18]. The green compacts were sintered at 5600C for one hour in a tubular vacuum furnace under argon gas atmosphere. After sintering all sintered specimens are kept cool for 3 h in the furnace itself. Similar procedure was followed to fabricate specimens of 0.5 wt% LM4 + Ta/NbC to 2 wt% LM4 + Ta/NbC. Fig. 1 shows the steps involved in powder metallurgy process. Fig. 2a shows the process of powder compaction using hydraulic press and Fig. 2b shows the images of developed specimens for wear test.
2. Experimental work 2.1. Materials and method The metal matrix nano composite are developed by considering aluminum LM4 as a matrix material. The chemical composition is shown in Table 1. The commercially available Tantalum niobium carbide (Ta/NbC) in the ratio of 60:40 is used as reinforcement material (As received average particle size of 150-200Nm and density of Ta/NbC is 10.8 gm/cc). The amount of Ta/NbC reinforcement varies from 0.5, 1, 1.5 and 2 wt%. The composites are developed through powder metallurgy technique (see Table 2). A weighed quantity of Aluminum LM4 powder of average particle size of 50 µm was first milled in a planetary ball mill for about 3 h to reduce the particle size. The ball to powder ratio was maintained at 25:1 in order to achieve uniformity throughout the powder particles [14–15]. A weighed quantity of Ta/NbC powder was pre heated to a temperature of 3000C to remove the oxidation of the powder particles. The pre heated Ta/NbC powder then mixed with milled aluminum LM4 alloy powder and milled for 15 min in order to get proper mixing of matrix and reinforcement particles. 2 wt% of Poly vinyl Alcohol (PVA) solution added to the mixed powder for proper bonding between the powder particles. Zinc stearate solution was applied throughout the die wall for proper lubrication and easy of ejection [20]. The mixed composite powders were then cold compacted in a hardened steel die at a pres-
Fig. 2a. Hydraulic press with compaction die.
Table 1 Chemical composition of matrix material Aluminum LM4. Elements
Si
Cu
Mn
Mg
Ni
Al
Wt%
6
3
0.4
0.2
0.3
bal
Table 2 List of factors and levels for wear test. Factors
Level 1
Level 2
Level 3
Level 4
Load (L) in N Sliding speed (S) in rpm Wt% of Ta/NbC (R)
10 200 0.5
20 400 1
30 600 1.5
40 800 2
Fig. 1. Steps involved in Powder metallurgy process.
Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043
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The formula used to calculate dry sliding wear rate was given below.
Wr ¼ DW=t gram=min
ð1Þ
A fixed sliding diameter of 100 mm was set for all the test runs. The wear parameters selected for the wear test are load, speed and weight percentage. The influence of some process parameters on dry sliding wear behaviour of aluminum matrix composites are well understood by taguchi technique [16]. Based on the number of factors and their levels L16 orthogonal array was selected for optimization. The experimental results are converted into a signal-to-noise (S/N) ratio. ‘‘Smaller is better” characteristic was taken for investigation of optimum wear rate of developed AMCs. The S/N ratio was calculated by using following Eq. (2).
S N ¼ 10log 1=nðy1 þ y2 þ þ ynÞ
ð2Þ
where, y1, y2 are the response values and n is the number of trials. ANOVA was used to identify the most influencing factor. The mean response table and S/N response tables are drawn from the mini tab software. The percentage of contribution of each individual factors are estimated by using ANOVA table. 3. Results and discussion 3.1. SEM analysis
Fig. 2b. Wear test specimen.
2.2. Experimental techniques 2.2.1. Microstructure examination The microscopic examination was carried out on powder samples and developed composites. The sintered samples were polished using emery papers of grit size 600 and 800. They were then polished using diamond paste using double disc polisher. The polished specimens etched with Keller’s reagent.
2.2.2. Dry sliding wear examination Dry sliding wear behavior of developed composite specimens are examined as per ASTM G99 standard [14]. The surface of the specimen was first cleaned with acetone in order to remove the contaminants. The wear rate was estimated by means of weight loss of the specimen per minute. Weight loss of the specimen was calculated by taking difference between the initial and final weight of the specimen. The specimen weight was recorded using electronic weight balancing machine of accuracy of 0.1 mg [15,21].
Fig. 3 shows the SEM images of LM4-Ta/NbC composites contain 1 wt% and 2 wt% of reinforcement. The uniform distribution of reinforcement were seen from the SEM images. Powder metallurgy method ensures the homogeneous distribution of Ta/NbC particles in the composite. Fig. 4 shows the microscopic images of the LM42 wt%Ta/NbC composites. 3.2. Taguchi design for wear rate optimization Wear rate experiments were carried out based on 4 level 3 factor orthogonal array L16. The results of wear rate based on Taguchi design was provided in Table 3. The experiment consist of 16 tests each test consist of different process parameters. The weight loss obtained due to dry sliding wear of aluminum LM4-Ta/NbC composites consisting of different weight percentage. Table 3 shows the wear test results. Figs. 5 and 6 shows the S/N ratio response table and mean response table respectively [19]. The highest response in the S/N ratio plot gives the optimum wear rate results. Fig. 6 shows the variation of mean value with the changes in control factors on the weight loss can be observed.
Fig. 3. SEM images of LM4-Ta/NbC composites.
Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043
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Fig. 4. Microscopic images of LM4-Ta/NbC composites.
Table 3 Experimental results using L16 orthogonal array. Sl No
Load (L) in N
Sliding speed (S) in rpm
Wt% of Ta/NbC (R)
Wear rate (Wr gm/min 103)
S/N ratio for wear rate (dB)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
10 10 10 10 20 20 20 20 30 30 30 30 40 40 40 40
200 400 600 800 200 400 600 800 200 400 600 800 200 400 600 800
0.5 1 1.5 2 1 0.5 2 1.5 1.5 2 0.5 1 2 1.5 1 0.5
0.2468 0.2532 0.2586 0.2662 0.2675 0.2892 0.2722 0.2822 0.2865 0.2675 0.3021 0.3134 0.2846 0.3008 0.3142 0.3371
12.15 11.93 11.75 11.50 11.45 10.78 11.30 10.99 10.86 11.45 10.40 10.08 10.92 10.43 10.06 9.44
Fig. 5. Main effect plot for S/N ratios.
Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043
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Fig. 6. Main effect plot for means.
‘‘Smaller is better” parameter was selected to identify the optimum wear characteristic of each process parameter. From the table it was observed that applied load has high influence on wear rate. As the applied load increases the wear rate increases. Also Sliding speed increases wear rate increases gradually and as weight percentage increase the wear rate decreases. The delta value was used to identify the most influencing parameters. From the S/N response Tables 4 and 5 it can be observed that the the optimum wear rate was observed at 1th level of applied load, 1st level of sliding speed and 4th level of wt % of reinforcement. The ranking of the parameters are based on the S/N response tables. Table 6 shows the ANOVA results of the tested specimens. From the ANOVA table it can be noticed that, applied load has the greater influence (65.74%) apart from the applied load sliding speed (19.74%) also having influence on wear rate and wt % of Ta/NbC (10.36%) less influence on wear rate. The level of significance of 0.05 and confidence level of 95% selected for the current investiga-
Table 4 S/N ratio response table. Level
Load (L) in N
Sliding speed (S) in rpm
Wt% of Ta/NbC (R)
1 2 3 4 Delta Rank
11.83 11.13 10.7 10.21 1.62 1
11.34 11.15 10.88 10.5 0.84 2
10.69 10.88 11.01 11.29 0.6 3
tion. The R2 value obtained was 95.83% which was within the confidence level. 3.3. Estimation of optimum response parameters of wear rate Optimization of response carried out by selecting the optimum values in the mean response table.
lWR ¼ L1 þ S1 þ R4 2 T
ð3Þ
where, T = overall mean of wear rate = 0.2839 103 gm/min
L1 ,S1 &R4 = optimum wear rate values obtained from Table 5.
L1
= 0.2562 103 gm/min
S1 = 0.2713 103 gm/min
R4 = 0.2726 103 gm/min lWR = (0.2562 103 + 0.2713 103 + 0.2726 103) 2 0.2839 103 lWR = 0.2323 103 gm/min The confidence level and the significant populations are calculated by using Eqs. (4) and (5).
CICE
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 1 1 ¼ F a ð1; f e ÞV e þ neff R
CIpop
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi F a ð1; f e ÞV e ¼ neff
ð4Þ
ð5Þ
where, F a ð1; f e Þ = The F ratio
Table 5 S/N ratio response table for means. Level
Load (L) in N
Sliding speed (S) in rpm
Wt% of Ta/NbC (R)
1 2 3 4 Delta Rank
0.2562 0.2778 0.2924 0.3092 0.053 1
0.2713 0.2777 0.2868 0.2997 0.0284 2
0.2938 0.2871 0.282 0.2726 0.0212 3
neff ¼
N 1 þ ðDOF associated in the estimate of mean responseÞ
neff = 16/(1 + 9) = 1.6 N = number of experiments = 16 R = 3 (Number of trials) Ve is the error variance = 6.4 105 (From ANOVA table)
Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043
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Table 6 Analysis of Variance for S/N ratio for wear rate. Source
DF
Seq SS
Adj SS
Adj MS
F-value
P-Value
p%
Load speed Ta/NbC wt% Error Total
3 3 3 6 15 S = 0.00800217
0.006062 0.00182 0.000955 0.000384 0.009221
0.006062 0.00182 0.000955 0.000384
0.002021 0.000607 0.000318 0.000064
31.55 9.47 4.97
0 0.011 0.046
65.74 19.74 10.36 4.17
R-Sq = 95.83%
F a ð1; f e Þ = 5.9874 (for 95% confidence level and 0.05 significant level from F chart) The calculated CICE = 0.019 andCIpop = 0.015 CI for Confirmation experiment: Mean lWR -CICE < lWR < Mean lWR + CICE 0.2133 103 gm/min < lWR < 0.2513 103 gm/min The 95% CI for population is: Mean lWR -CIpop < lWR < MeanlWR + CIpop 0.2173 103 gm/min
R-Sq(adj) = 89.58%
4. Analysis of wear mechanism The wear mechanism of worn out surfaces was influenced by varying factors. Increase in the applied load, increases the frictional force between the pin and disc material and makes the delamination on the pin material. The SEM images of the worn surface and debris formed during high load and higher shear force are shown in Fig. 7(a–d). Finer debris were formed during low load condition due to lower friction between the surfaces. During initial condition the increase in the sliding speed gradually increases the wear rate at certain point of contact the thermal softening of the pin material influences more rate of wear during high sliding speeds. Due to thermal softening higher delamination and peeling of material particles took place from the surface of the pin material. But in some cases the increase in the sliding speed decreases the wear rate. The
Table 7 Confirmation experiment results along with predicted values. Response
Combination of Process variables (optimal)
Predicted optimal value
Predicted confidence interval at 95% confidence level
Confirmation experiment value
Wear rate
L1S1R4
0.2323 103 gm/min
0.2133 103 gm/min < lWR < 0.2513 103 gm/min 0.2173 103 gm/min < lWR < 0.2473 103 gm/min
0.2569 103 gm/min
Fig. 7. (a–d): The SEM images of the worn surface and debris formed during high load.
Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043
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reason behind this was due to continuous rubbing of the pin surface the asperities on the pin surface will become flat and results in adhesive type of wear mechanism. 5. Conclusion The following conclusions were drawn from the present research investigation; The LM4-Ta/NbC composites are produced by using powder metallurgy technique. The SEM images of the composite shows the uniform distribution of Ta/NbC particles and ensures that powder metallurgy is one of the effective method to fabricate composites. Taguchi method is used to optimize the process parameters and were identified for minimum wear rate are; Load 10 N, sliding speed = 200 rpm and wt% of Ta/NbC reinforcement = 2 wt%. From ANOVA results it is confirmed that applied load (65.74%), Sliding speed (19.74%) and Ta/NbC reinforcement (10.36%) influence on wear rate.
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Please cite this article as: T. S. Sachit, N. Mohan, R. Suresh et al., Optimization of dry sliding wear behavior of aluminum LM4-Ta/NbC nano composite using Taguchi technique, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2019.09.043