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International Journal of Metalcasting

, Volume 13, Issue 2, pp 354–366 | Cite as

Optimisation of Dry Sliding Wear Parameters of Squeeze Cast AA336 Aluminium Alloy: Copper-Coated Steel Wire-Reinforced Composites by Response Surface Methodology

  • Samson Jerold Samuel ChelladuraiEmail author
  • Ramesh Arthanari
  • Rohith Selvarajan
  • Thirumal Prasanna Ravichandran
  • Saravana Kumar Ravi
  • Siva Rama Chandran Petchimuthu
Article

Abstract

Copper-coated steel wires (5 numbers) were uniformly reinforced in AA336 aluminium alloy using squeeze casting process. Microstructure of castings was examined, and dry sliding wear test was performed by considering the factors viz., load (10–50 N), velocity (1–5 m/s) and sliding distance (500–2500 m). Response surface methodology was used to design the experiments by considering three factors, five levels central composite design. A regression model was developed to predict the weight loss of composites and checked its adequacy using significance tests, analysis of variance and confirmation tests. Worn surfaces of composite were investigated using field emission scanning electron microscope and reported with wear mechanisms. Dry sliding wear parameters were optimised for obtaining minimum weight loss. Microstructure of casting showed the reinforcement of steel wires in AA336 aluminium alloy and copper coating on steel wires offered better interface bonding between matrix and reinforcement. Response surface plots revealed that weight loss of composites increased with increasing load and sliding distance. Worn surface of composites showed fine grooves at lower loads and delamination was observed at higher loads. 18.1 N load, 2.41 m/s velocity and 2094 m sliding distance were observed as optimum dry sliding wear parameters for obtaining minimum weight loss.

Keywords

AA336 aluminium alloy squeeze casting steel wire microstructure response surface methodology wear 

Introduction

Aluminium-based metal matrix composites have been widely used in aerospace, automotive, transportation and marine engineering applications because of its high specific strength, stiffness, lower weight, excellent resistance to wear and corrosion.1, 2, 3, 4, 5 Researchers are developing a novel composite that offers superior mechanical properties with excellent wear resistance. Composites consist of two or more materials which completely differ in physical and chemical and properties. The major constitution is matrix, and reinforcements have been added to improve the mechanical properties viz., hardness, tensile strength and wear resistance. In this present work, AA336 aluminium alloy has been selected as matrix because of its high silicon content and its mainly used as pistons in automotive and aerospace applications.6 Reinforcements such as aluminium oxide, silicon carbide, boron carbide, titanium carbide, steel fibres, titanium diboride and fly ash improved the hardness, tensile strength and wear resistance of aluminium alloy.7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 However, addition of reinforcement decreased the ductility of composites. Out of these reinforcements, steel wires have been selected in this present work because of its superior strength, excellent wear resistance, high elastic modulus and low coefficient of thermal expansion.21

Aluminium-based composites have been fabricated using various processes such as spray co-deposition, diffusion bonding, powder metallurgy, in situ solidification and casting process. Among all manufacturing processes, casting process is widely accepted as most simple, viable and economical method for producing composites. In casting process, squeeze casting technique is a promising technique to produce near net shaped components which offer superior mechanical properties and wear resistance compared to gravity die casting.22, 23, 24, 25, 26 In this process, a premeasured molten metal is poured into a die and allowed to solidify under a constant pressure.

Gecu et al.27,28 studied the effect of preform preheating on wear behaviour of 304 stainless steel-reinforced A356 matrix composite and investigated the hardness and compressive residual stress. The authors observed double-layered intermetallic compounds viz., Fe4Al13 and Fe2Al5 phases at the interface of aluminium and stainless steel. These reaction phases increased the hardness, compressive residual stress and wear resistance. On the other hand, when the sample was not preheated or preheated excessively, interface bonding was weakened and crack propagation occurred. The authors also reported that inadequate and excessive preform preheating adversely affected the dry sliding wear resistance while sufficient preheating (30 min) improved the tribological properties of 304 stainless steel-reinforced A356 matrix composite.

The intermetallic compounds between matrix and reinforcements can be prevented by using suitable coating on reinforcements.29,30 The authors group have studied the effect of copper coating on steel wire-reinforced composite and compared its mechanical properties with uncoated steel wire-reinforced composite and reported their findings.30 The results reveal that copper-coated steel wire-reinforced composite exhibited better mechanical properties over uncoated steel wire-reinforced composite. Hence, in this research work, copper-coated steel wires have been reinforced in AA336 aluminium alloy.

The authors’ group has investigated31 the effect of steel wires reinforcement (1–5 numbers) on AA336 aluminium alloy using squeeze casting process and studied the mechanical properties and wear resistance of composites. The results reveal that wear weight loss of composites decreased with increasing numbers of steel wires reinforcement in AA336 aluminium alloy and increased with increasing load. Hence, AA336 aluminium alloy reinforced with five numbers of steel wires have been chosen in this present work and studied the effect of dry sliding parameters viz., load, velocity and sliding distance on weight loss of composites. In addition, dry sliding process parameters viz., load, velocity and sliding distance have been optimised for obtaining minimum weight loss. Also a maximum of of five numbers of steel wires can be reinforced in a wear sample of 10 mm diameter with 35 mm height. Hence, five numbers of steel wires have been chosen for this work.

Dry sliding wear parameters viz., load (10–50 N), velocity (1–5 m/s) and sliding distance (500–2500 m) were considered. Three factors, five levels central composite design was selected and experiments were designed using response surface methodology (RSM). Many researchers have used central composite design for their research work and developed mathematical model to predict the response.32, 33, 34 Microstructure of the castings was investigated using scanning electron microscope and image analysis system. Dry sliding wear test was conducted as per experimental design using pin-on-disc tribometer at room temperature. Weight loss of samples was calculated by measuring initial and final weight of pin. A regression model was developed to predict the weight loss of composites and checked its adequacy by means of significance tests, analysis of variance and confirmation tests. Worn surface of samples was investigated using field emission scanning electron microscope (FESEM) and reported with wear mechanisms. Also the specific wear rate of composites was discussed. The main objective of this research work is to develop a mathematical model to predict the weight loss of composites and analyse the influence of dry sliding wear parameters viz., load (L), velocity (V) and sliding distance (D) on weight loss of composites.

Materials and Methods

Universal testing machine as shown in Figure 1 was modified and used to apply pressure during the solidification in direct squeeze casting process. A cylindrical die was used to prepare the castings, and it was made up of SG400 spheroidal graphite iron. A ceramic electric heater was used to preheat the die which had the maximum heating capacity up to 400 °C.
Figure 1

Universal testing machine modified for squeeze casting process.

Schematic diagram of AA336 aluminium alloy embedded with copper-coated steel wires as shown in Figure 2. Commercially available steel wire with chemical composition as given in Table 1 was selected as reinforcement. Steel wires were copper coated using electroless plating technique, and the thickness of copper coating was measured and found to be 64 µm. A circular plate of 60 mm diameter with 15 mm height was taken, and microholes were made using wire cut electrical discharge machine to hold the copper-coated steel wires inside the die. The circular plate with steel wires arrangement were placed inside the die and preheated to 225 °C.
Figure 2

Schematic diagram of copper-coated steel wire reinforcement in AA336 aluminium alloy casting.

Table 1

Chemical Composition of Steel Wire (wt%)

Sample

C

S

Mn

P

Si

Cr

Ni

Cu

Fe

FeCu (wt%)

0.12

0.01

7.52

0.04

0.3

17.9

4.4

1.17

Bal

Chemical composition of AA336 aluminium alloy as given in Table 2 was melted by electric resistance furnace having the capacity of 5 kg. The melt was degassed using hexachloroethane tablets to remove the hydrogen, and melt temperature was raised to 750 °C to facilitate the bonding around the steel wire. While the use of an inert gas like argon was considered, due to the melt capacity and furnace configuration leading to safety concerns requiring need for additional care to connect the argon gas cylinder, it was decided to use hexachloroethane (C2Cl6) tablets to entrap the gases. A measured quantity of molten metal was poured directly into the preheated die and pouring was done manually using a ladle. Subsequently, a constant pressure of 125 MPa was applied on the melt using EN8 steel punch for a delay time of 60 s produced cylindrical castings of 60 mm diameter with 75 mm height and shown in Figure 3. Steel wires will not deflect while applying load during composite fabrication, since the height of steel wires (50 mm) is lower than the height of casting (75 mm).
Table 2

Chemical Composition of AA336 Aluminium Alloy (wt%)

Sample

Si

Fe

Cu

Mn

Mg

Ni

Pb

Ti

Al

AA336 (wt%)

10.8

0.51

1.3

0.12

0.86

0.72

0.01

0.05

Bal

Figure 3

Sample casting produced by squeeze casting process.

Samples were prepared to investigate microstructure and hardness of composites. Microstructure of sample was investigated using scanning electron microscope and image analysis system to examine the reinforcement of copper-coated steel wire in AA336 alloy. Hardness of castings was investigated using Brinell hardness tester (Model KB—3000H and Krystal equipment’s make, India) with a load of 500 kg and a dwell time of 15 s. Hardness test was repeated for four times, and the average hardness value is presented.

Design of Experiments Using Response Surface Methodology

Dry sliding process parameters viz., load (10–50 N), sliding distance (500–2500 m) and sliding velocity (1–5 m/s) were considered, and design expert version 10 was used to design the experiments. Three factors and five levels central composite design was selected, and it generated 20 experimental runs. Dry sliding wear test process parameters, and their levels are reported in Table 3. The objective function of this present optimisation is to minimise the weight loss of AA336—copper-coated steel wire-reinforced composites. Weight loss of composites was calculated using initial weight and final weight (Eqn. 1).
$$ {\text{WL}} = m_{1} - m_{2} $$
(1)
where WL is weight loss (g), m1 is initial weight of pin (g) and m2 is final weight of pin (g).
Table 3

Dry Sliding Wear Parameters and Their Levels

Parameters

Levels

Load (N)

10

18

30

42

50

Sliding distance (m)

500

905

1500

2095

2500

Velocity (m/s)

1

1.8

3

4.2

5

Also a second-order polynomial regression equation as shown in Eqn. 2 was developed to predict the response by correlating the input parameters.
$$ {\text{WL}} = c_{0} + \sum c_{1} x_{i} + \sum c_{2} x_{i} x_{j} + \sum c_{3} x_{i}^{2} $$
(2)
where WL is weight loss of composite, c0, c1, c2 and c3 are coefficients. The second term (xi) represents linear effect; third term \( (x_{i} x_{j} ) \) denotes interaction effect, and the fourth term (x i 2 ) indicates second-order effect.

Dry Sliding Wear Test

Samples of 10 mm diameter with 35 mm height were prepared according to ASTM G99 standard and dry sliding wear test was conducted using pin-on-disc wear testing apparatus (Model TR-20LE-M108 and Ducom make, India). Pin-on-disc tribometer consists of a steel disc with 64HRc hardness, and the samples were rotated against the steel disc, producing sliding wear at room temperature. A lever arrangement was used to apply the load which makes the contact between rotating disc and stationary pin.

Steel disc was polished using emery sheets to obtain a clean scratch free surface, and the samples were cleaned with acetone before and after every run. The experiments were conducted at an ambient temperature of 32 °C, relative humidity of 64% with wear scar diameter of 10 mm. Wear test was carried out based on experimental design, and the weight of sample was measured using electronic weighing balance with an accuracy of 0.001 mg. Weight loss of samples was calculated using weight of the pin before and after wear test.

Results and Discussion

Microstructure

Microstructure of AA336 aluminium alloy-copper-coated steel wire-reinforced composite was examined using scanning electron microscope and shown in Figure 4a–d. The reinforcement of copper-coated steel wire in AA336 aluminium alloy can be seen. During the composite preparation, steel wires were placed inside the die with suitable arrangement and molten metal was poured to produce castings. Copper coating on steel wires showed a better interface bonding between steel wire and AA336 aluminium alloy. A constant squeeze pressure applied during the solidification of castings minimised the porosity which results in fine grain structure. Similar results have been reported in other studies29,35 that copper coating on reinforcement offers better interface bonding between matrix and reinforcement.
Figure 4

Micrographs of AA336 aluminium alloy-copper-coated steel wire-reinforced composite.

Microstructure of composites was examined using image analysis system and shown in Figure 5a–c. The micrographs revealed the reinforcement of copper-coated steel wire in AA336 aluminium alloy. In addition, a better interface bonding between matrix and reinforcement was observed due to the presence of copper coating on reinforcement.
Figure 5

Optical micrographs of AA336 aluminium alloy-copper-coated steel wire-reinforced composite.

Copper-coated steel wire-reinforced composite was examined using energy-dispersive X-ray spectroscopy (EDS) and shown in Figure 6. It revealed the presence of major constitutions in matrix such as Al, Si and reinforcement (Fe). Also copper (Cu) was observed at the interface of aluminium and steel wire. This may be attributed to the effect of copper coating on reinforcement which prevents the formation of Al/Fe intermetallic compounds at the interface of matrix and reinforcement.
Figure 6

EDS spectrum of AA336 aluminium alloy with copper-coated steel wire composite.

Characterisation of Dry Sliding Wear

Three parameters (load, velocity and sliding distance), five levels were considered and experiments were designed using response surface methodology (RSM) and presented in Table 4. Three trials were performed for each experiment, and average weight loss of composite was presented. During the dry sliding wear test, it was observed that weight loss of pin decreased due to the reinforcement of hard copper-coated steel wires in AA336 aluminium alloy and the authors group reported.31
Table 4

Experimental Design Matrix and Results of Weight Loss

Test run

Load (N)

Velocity (m/s)

Sliding distance (m)

Weight loss (g)

1

10

3

1500

0.0124

2

18

2

905

0.0128

3

18

2

2095

0.0121

4

18

4

905

0.014

5

18

4

2095

0.0116

6

30

1

1500

0.0195

7

30

3

500

0.0069

8

30

3

1500

0.0135

9

30

3

1500

0.0139

10

30

3

1500

0.0197

11

30

3

1500

0.0131

12

30

3

1500

0.0128

13

30

3

1500

0.0169

14

30

3

2500

0.0219

15

30

5

1500

0.0123

16

42

2

2095

0.0328

17

42

2

905

0.0125

18

42

4

2095

0.0331

19

42

4

905

0.0064

20

50

3

1500

0.022

From the analysis of variance, it was observed that R2 and adjusted R2 values were found as 92.45 and 87.24%, respectively. These values were close to each other, and the dry sliding wear parameters were tested for significance at 95% confidence level. Significant wear parameters were considered in regression equation, and insignificant parameters were removed without affecting the accuracy. It was observed that load, sliding distance and interactions of load–velocity were found to have more significant effects on weight loss of composites. Velocity, interaction of load and velocity, interaction of velocity and sliding distance have the p value greater than 0.10 which were not significant. A regression equation was obtained for predicting the weight loss and is given as
$$ {\text{WL}} = \, c_{0} + c_{1} L \, + c_{2} D \, + c_{3} LD $$
(3)
where WL is weight loss of specimen (g), c0, c1, c2 and c3 are regression coefficients, L is load applied in normal direction (N), and D is sliding distance (m). The coefficients of regression equation are listed in Table 5.
Table 5

Coefficients of Regression Equation for Weight Loss of AA336-Copper-Coated Steel Wire Reinforced Composites

Regression coefficients

Coefficients

R2

c 0

c 1

c 2

c 3

Value

0.035484

− 0.000845

− 0.000020

0.0000000884

0.924

This developed regression equation can predict the weight loss of composites with respect to dry sliding input parameters viz., load, velocity and sliding distance. To check the adequacy of regression equation, confirmation tests were performed by selecting new sets of wear parameters which differed from the experimental design developed using response surface methodology. Weight loss was measured for the confirmation tests and compared with predicted weight loss and the results are reported in Table 6. The percentage of error was calculated using experimental and predicted weight loss and the error percentage was within ± 8, which confirms that the developed regression equation can be used to predict the weight loss of composites with greater accuracy.
Table 6

Comparison of Weight Loss Using Regression Analysis and Experimental Results

Test run

Load (N)

Velocity (m/s)

Sliding distance (m)

Actual weight loss (g)

Predicted weight loss (g)

Error (%)

1

15

1.5

1200

0.0034

0.00040

7.55

2

25

2.5

2400

0.0058

− 0.02833

− 1.20

3

35

3.5

3600

0.0084

− 0.0639

− 1.13

The relationship between actual and predicted weight loss is shown in Figure 7. A good relationship between predicted and actual weight loss was observed, and it shows that values were scattered on both sides and the slope was close to unity.
Figure 7

Scatter diagram for weight loss of AA336 aluminium alloy-copper-coated steel wire-reinforced composites.

Analysis of variance for weight loss is reported in Table 7. The significance of each term in regression model is checked at 95% confidence level and 5% significance level. It was observed that load, sliding distance and interaction of load-sliding distance have significance in weight loss (p value < 0.05). Also the lack of fit has F value 0.78, which was lesser than the standard F value of 5.05 (95% confidence level); hence, the developed regression equation was adequate and it can be used to predict the weight loss within these dry sliding input parameters and their levels.
Table 7

Analysis of Variance for Weight Loss

Source

Sum of squares

Degree of freedom

Mean square

F value

p value

Model

0.0009

6

0.0001

22.65

< 0.0001*

Load (N)

0.0002

1

0.0002

28.79

0.0001*

Velocity (m/s)

0.0000

1

0.0000

3.38

0.0891

Sliding distance (m)

0.0004

1

0.0004

54.15

< 0.0001*

Load (N) × velocity (m/s)

0.00000521

1

0.00000521

0.8052

0.3859

Load (N) × sliding distance (m)

0.0003

1

0.0003

48.35

< 0.0001*

Velocity (m/s) × sliding distance (m)

0.00000271

1

0.00000271

0.4190

0.5287

Residual

0.0001

13

0.00000647

  

Lack of fit

0.0000

5

0.00000585

0.78

0.6402

Pure error

0.0000

5

0.00000748

  

Total

0.0010

19

   

R Squared: 0.9245; Adj R Squared: 0.8724

*Significant at p < 0.05

Figures 8, 9 and 10 show the response surface plot of actual weight loss for all pairs of dry sliding wear parameters. The interaction of load and velocity with weight loss is shown in Figure 8. It can be seen that weight loss of composites increases with increasing load at all levels of velocity and sliding distances (Figures 8 and 10). During the experimental work, load was applied through a lever arrangement, which makes the pin contact to the rotating steel disc. The contact between pin and disc decreases as load increases from 10 to 50 N. This increases the temperature at the interface which results in increased weight loss. Radhika et al.15 and Mandal et al.35 also reported the same trend that weight loss of samples increases with increasing load.
Figure 8

Response surface plot of weight loss as a function of load and sliding velocity for a constant sliding distance of 1500 m.

Figure 9

Response surface plot of weight loss as a function of sliding velocity and sliding distance for a constant load of 30 N.

Figure 10

Response surface plot of weight loss as a function of load and sliding distance for a constant sliding velocity of 3 m/s.

It can be seen that weight loss of composites decreases with increasing velocity from 1.8 to 4.2 m/s (Figures 8 and 9). The contact time between pin with disc was more when the samples tested at lower levels of velocity which results in more weight loss. As velocity increases from 1.8 to 4.2 m/s, the temperature at the interface between pin and disc increases which forms a mechanically mixed layer (MML) over the surface of pin. This layer prevents the pin from adhesive wear which minimises the weight loss of composites. Similar wear mechanism was observed in other studies36,37 that weight loss of composites decreases with increase in velocity.

The interaction of load and sliding distance with weight loss is depicted in Figure 10. It was observed that weight loss of composites increased with increasing sliding distance at all levels of load and higher amount of weight loss was observed at higher loads. However, weight loss of composites was lower at higher levels of velocity compared to lower level of velocity (Figure 9). This is due to presence of copper-coated steel wires that protrudes at the surface which establishes contact with the counterface and minimised the contact of matrix with sliding surface. Few researchers38,39 also reported the same mechanism that uniform contact between pin surface and disc resulted in minimum weight loss of specimen.

Optimisation of Dry Sliding Parameters

Dry sliding parameters viz., load of 10–50 N, velocity of 1–5 m/s and sliding distance of 500–2500 m were considered in this present work. Experiments were carried out based on experimental design developed using response surface methodology. Weight loss of samples was measured and response surfaces present the interaction of load, velocity and sliding distance with weight loss. The objective function of optimisation is to obtain minimum weight loss for AA336 aluminium alloy reinforced with copper-coated steel wires. A minimum weight loss of 0.0064 g (Table 4) was observed during experimental work. Hence, the target weight loss of 0.00639 g was given as input in optimisation process, which is lesser than the minimum experimental weight loss (0.0064 g). A load of 18.1 N, velocity of 2.41 m/s and a sliding distance of 2094 m were observed as the optimum dry sliding wear parameters for the weight loss of 0.00639 g.

Worn Surface Analysis

Figure 11a–c shows the worn surface of AA336 aluminium alloy reinforced with copper-coated steel wires tested at dry sliding conditions. Figure 11a shows the worn surface of composite tested at 10 N load. It can be seen that the presence of fine grooves parallel to the sliding direction and shallow grooves were observed in some regions. This may be attributed to the presence of hard copper-coated steel wires which act as load bearing elements which avoids the contact between pin and disc. These copper-coated steel wires would bear the load and prevent the transfer of load to the matrix, resulting in minimum weight loss. Worn surface of composite tested at 30 N is depicted in Figure 11b. It was observed that continuous grooves parallel to the sliding direction and delamination was observed at some regions. During the wear test, it was observed that weight loss of composites increases while increasing load from 10 to 30 N. The contact between pin and disc reduces which results in more amount of material removal from the pin. Wear debris slide along the surface of pin, while counter face rotates continuously, resulting in continuous grooves on the surface of specimen. Figure 11c shows the worn surface of composite tested at 50 N. It reveals deep continuous grooves with local delamination on the surface of pin. This may be attributed to the generation of high temperature at the interface of pin and disc. As load increases from 30 to 50 N, more heat was generated due to friction which results in removal of more material with deformation. Wear mechanism of composites changes from adhesion to severe delamination when load increases from 10 to 50 N. These results have been verified with wear trends as observed from the response surface plots (Figures 8 and 9) that weight loss of composites increased linearly with increasing load from 10 to 50 N. The same phenomenon has been observed in a previous study39 that weight loss of composites increases with increasing load.
Figure 11

Worn surfaces of AA336 aluminium alloy-copper-coated steel wire-reinforced composite tested at various conditions: (a) L = 10 N, V = 3 m/s, D = 1500 m; (b) L = 30 N, V = 3 m/s, D = 1500 m; (c) L = 50 N, V = 3 m/s, D = 1500 m; L load, V velocity and D sliding distance.

Worn surface of composite tested at optimum conditions [L = 18.1 N, V = 2.41 m/s, D = 2094 m] is shown in Figure 12. Accuracy of developed regression model was checked by investigating the worn surface of composite tested at optimum dry sliding wear parameters. It was observed that fine grooves on the surface which results in minimum weight loss. This ensures that the developed regression model can be used to predict the weight loss within the ranges of load, velocity and sliding distance.
Figure 12

Worn surface of AA336 aluminium alloy-copper-coated steel wire-reinforced composite tested at optimum condition L = 18.1 N, V = 2.41 m/s and D = 2094 m.

In general, weight loss of composites increases with increasing load and sliding distance, but the severity of wear was delayed at all loading conditions. This is due to the higher hardness of composite surface, as the composite has the surface hardness of 60 BHN which resists the level of deformation at all loading conditions. Hardness of composites can be increased by reinforcing copper-coated steel wires in AA336 aluminium alloy which minimises the amount of weight loss at all loading conditions. By reinforcing hard steel wires in AA336 aluminium alloy, hardness of 96 BHN and 136 BHN were observed at the interface of aluminium alloy-steel wire and steel wire, respectively. The lower weight loss can also relate to the aluminium alloy. AA336 aluminium alloy has high silicon content of 10.9%, and offers higher hardness which results in wear resistance to matrix. Also application of squeeze pressure during the manufacturing process minimised the porosity and offered fine grain structure. Further, silicon and magnesium in aluminium alloy promotes the wettability and copper coating on steel wires and offered better interface bonding between matrix and reinforcement. This minimised the amount of weight loss at all testing conditions.

Analysis of Specific Wear Rate

Specific wear rate of composite was calculated using Eqn. 4, and the results are reported in Table 8. Volume loss of pin was calculated using weight loss and density.
$$ {\text{SWR}} = \frac{\text{VL }}{L D} $$
(4)
where SWR is specific wear rate (mm3/N m), VL is volume loss of pin (mm3), L is load (N) and D is sliding distance (m)
Table 8

Specific Wear Rate of AA336 Aluminium Alloy-Copper-Coated Steel Wire Reinforced Composite

Test run

Load (N)

Velocity (m/s)

Sliding distance (m)

Specific wear rate (mm3/N m)

1

10

3

1500

0.000297

2

18

2

905

0.000283

3

18

2

2095

0.000115

4

18

4

905

0.000309

5

18

4

2095

0.000111

6

30

1

1500

0.000156

7

30

3

500

0.000165

8

30

3

1500

0.000108

9

30

3

1500

0.000111

10

30

3

1500

0.000157

11

30

3

1500

0.000105

12

30

3

1500

0.000102

13

30

3

1500

0.000135

14

30

3

2500

0.000105

15

30

5

1500

0.000098

16

42

2

2095

0.000134

17

42

2

905

0.000118

18

42

4

2095

0.000135

19

42

4

905

0.000061

20

50

3

1500

0.000106

The interaction of load, velocity and sliding distance on specific wear rate of composites are shown in Figures 13, 14 and 15. It can be seen that specific wear rate of composites decreased with increasing sliding distance and load. This may be attributed due to the reinforcement of hard copper-coated steel wires in aluminium alloy which significantly decreased the weight loss of composites. Also the specific wear rate of composites decreased with increasing sliding velocity.
Figure 13

Response surface plot of specific wear rate as a function of load and sliding velocity for a constant sliding distance of 1500 m.

Figure 14

Response surface plot of specific wear rate as a function of load and sliding distance for a constant sliding velocity of 3 m/s.

Figure 15

Response surface plot of specific wear rate as a function of sliding velocity and sliding distance for a constant load of 30 N.

Conclusion

Copper-coated steel wires (5 numbers) were uniformly reinforced in AA336 aluminium alloy using squeeze casting process. Microstructure of cast samples was investigated, and dry sliding wear test was performed by varying parameters viz., load, velocity and sliding distance. Response surface methodology was used to design the experiments and the regression model was been developed to predict the weight loss of composites. Dry sliding wear parameters were optimised for obtaining minimum weight loss and worn surface of samples were investigated using field emission scanning electron microscope. The main conclusions drawn from the present work are as follows:
  1. 1.

    Microstructure of cast samples showed the reinforcement of copper-coated steel wire in AA336 aluminium alloy and copper coating on steel wire offered better interface bonding between matrix and reinforcement.

     
  2. 2.

    A regression model was developed to predict the weight loss of composites. Confirmation tests were performed by selecting new sets of wear parameters which differed from the experimental design developed using response surface methodology. Error percentage was with in ± 8% by comparing experimental and predicted weight loss of confirmation tests.

     
  3. 3.

    Response surface plots revealed that weight loss of composites increased with increasing load and sliding distance at all levels of velocity. However, weight loss decreased with increasing velocity.

     
  4. 4.

    Specific wear rate of composites decreased with increasing load, velocity and sliding distance.

     
  5. 5.

    A load of 18.1 N, velocity of 2.41 m/s and a sliding distance of 2094 m were found as optimum dry sliding wear parameters for obtaining minimum weight loss.

     
  6. 6.

    Worn surface of composites showed fine grooves at lower loads and delamination was observed at higher loads resulting in higher amount of weight loss.

     

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Copyright information

© American Foundry Society 2018

Authors and Affiliations

  • Samson Jerold Samuel Chelladurai
    • 1
    Email author
  • Ramesh Arthanari
    • 2
  • Rohith Selvarajan
    • 1
  • Thirumal Prasanna Ravichandran
    • 1
  • Saravana Kumar Ravi
    • 1
  • Siva Rama Chandran Petchimuthu
    • 1
  1. 1.Department of Mechanical EngineeringSri Krishna College of Engineering and TechnologyCoimbatoreIndia
  2. 2.Department of Mechanical EngineeringSCAD Institute of TechnologyPalladam, TirupurIndia

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