- Email: [email protected]
Tribological properties of journal bearings manufactured from particle reinforced Al composites
Materials and Design 30 (2009) 1381–1385
Contents lists available at ScienceDirect
Materials and Design journal homepage: www.elsevier.com/locate/matdes
Short Communication
Tribological properties of journal bearings manufactured from particle reinforced Al composites Bekir Sadık Ünlü a,*, Enver Atik b,1 a b
Celal Bayar University, Vocational High School, Department of Machinery, 45400-Turgutlu-Manisa, Turkey Celal Bayar University, Engineering Faculty, Department of Mechanical Engineering, 45140-Muradiye-Manisa, Turkey
a r t i c l e
i n f o
Article history: Received 21 April 2008 Accepted 30 June 2008 Available online 15 July 2008
a b s t r a c t In this study, journal bearings were manufactured from composite structures by casting method reinforcing 3% (Al2O3 and SiC) and (3% Al2O3 + 3% SiC) into pure Al. Tribological properties of these bearings were investigated by wear experiments at lubricated conditions under 20 N load and 1500 rpm on the radial journal bearing wear test rig. Effects of these composites on wear properties were investigated. Consequently, tribological properties of these particle reinforced composite bearings have significantly improved. In addition, particle reinforced Al composites were used to produce journal bearing. Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction Metal matrix composites (MMCs) are obtained by adding hard particles such as Al2O3 and SiC into Al alloys to have good mechanical properties. These composites are used as cutting tools, bearing parts, and medical rigs. Many methods were developed to add these particles into pure Al [1,2]. There have been a lot of studies dealing with application problems of these methods [3]. Seramic reinforced Al alloys are used due to their good wear resistance and low density in automotive industry [4]. Yield strength of Al–Cu alloys decrease by adding SiC but their hardness and sliding properties increase. Tribological properties of these materials are higher than those of Al–SiC [5–7]. In addition, Al–Al2O3 composites having good mechanical and tribological properties are used in crank bearings and motor blocks in order to improve wear resistance [8,9]. Al alloys containing Cu, Mg, Si, and Sn are used as bearing materials [10]. Until the early 1940’s, white metal was used and then Al alloys were used as bearing materials [11]. Al alloys can be used in environments where corrosion is a problem. Wear resistance of Si added Al alloys is higher than those of the other Al alloys [12]. Al–Si alloys have good castability, thermal conductivity, and weldability, high strength and excellent corrosion resistance. They are used in pistons and bearings due to these properties. Si particles can be distributed into structure uniformly, thus material hardness increases [13,14]. In addition, Al–Mg–Si alloys are used due to excellent sliding properties in tribology applications. These
* Corresponding author. Tel.: +90 2363124888; fax: +90 2363144566. E-mail addresses: [email protected] (B.S. Ünlü), [email protected] (E. Atik). 1 Tel.: +90 2362412144; fax: +90 2362412143. 0261-3069/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2008.06.069
properties are high strength, high deformability and good wear resistance [15]. Finally, particle reinforcements may also be added to Al–Mg alloys. These alloys have low strength because of high heat friction. These properties are improved by adding SiC [16]. Therefore; these particle reinforced composites may be used as journal bearing material [17]. These metal matrix composites are used in journal bearing, piston, cylinder and aircraft brake applications. The tribological properties of these materials are improved by adding SiC [18]. In this study, tribological properties of journal bearings manufactured from composite structures by casting method pure Al, particle reinforced, 3% (Al2O3 and SiC), and (3% Al2O3 + 3% SiC) were investigated. 2. Experimental studies 2.1. Preparation of experimental materials In this study, pure Al (99% purity), Al based (3% Al2O3 and SiC, and 3% Al2O3 + 3% SiC) particle reinforced materials have been used as journal bearing and SAE 1050 material as shaft (journal). The chemical compositions of the materials used in the experiments were given in Table 1. Dimensions of bearing specimens were as follows: inner diameter (d = 10+0.05 mm), width (B = 10 mm), outer diameter (D = 15 mm). The specimens have been worn and friction coefficient have been measured at radial journal bearing wear test rig at lubricated condition according to the procudure by Atik et al. [19] and Ünlü and Atik [20]. The wear losses have been measured on lubricated conditions of 20 N loads, 1500 rpm (v = 0.785 m/s velocity) and every 30 min for 2.5 h (7065 m sliding distance). Lubricating has been done by SAE 90 gear oil. The specimens were cleaned. The microstructures of wear surfaces have been photographed using
1382
B.S. Ünlü, E. Atik / Materials and Design 30 (2009) 1381–1385
Table 1 Chemical composition of journal material (wt.%)
Table 3 Surface roughness of bearing materials
Material
C
Si
Mn
P
S
Fe
Roughness (lm)
Al
Al–Al2O3
Al–SiC
Al–Al2O3–SiC
SAE 1050
0.51
0.3
0.7
0.04
0.05
Balance
Before wear After wear
3.16 4.92
2.34 2.91
0.65 0.72
1.12 1.24
Materials
Al
Al–Al2O3
Al–SiC
Al–Al2O3–SiC
Hardness (HB)
40
66
62
63
optical and scanning electron microscope. In addition, hardness has been measured using a macrotester type (Table 2). Surface roughness tests have been performed on Mitutoyo-CE surface roughness test rig.
Friction Coefficient (μ)
Table 2 Hardness of bearing materials
0.08
Al
0.06
Al-AlO 0.04
Al-SiC
0.02
Al-ALOSiC
0 0
0.5
1
1.5
2
2.5
Time (h) 2.2. Radial journal bearing wear test rig
3.1. Hardness and surface roughness properties
45
Al 40
Al-AlO Al-SiC
35
Al-ALOSiC 30 0
0.5
1
1.5
2
2.5
Time (h) Fig. 3. The bearing temperature–time variation Al composite bearings.
2.5
Wear Loss (mg)
3. Results and discussion
Temperature (ºC)
Fig. 2. The friction coefficient-time variation Al composite bearings.
Bearings materials in journal bearings are generally selected from materials which have lower wear strength than the shaft material, thereby lowering the wearing of the shaft significantly. For this reason, journal bearing wear test apparatus are designed to examine the wearing of bearing materials. In this study, a special bearing wear test apparatus has been designed to examine the wearing behavior of bearing material and the shaft together. Therefore, it is possible to investigate different bearing and shaft materials and the effects of heat treatments on these materials. Such a mechanism provides wear of bearings rather than using standard methods as this is more appropriate direct [19]. The system is formed by a weight applied by a rigid bar, a steel bar connected to the bearing from a distance and a comparator. Friction coefficient is determined from the friction force formed along the rotating direction of the bearing and from the movement of the steel bar connected to the bearing [20]. Radial wear test rig is illustrated in Fig. 1. In the experiments under lubricated conditions, very little movement was taken place for high comparator’s spring coefficient and low friction. Therefore, a tensile spring of k = 0.004 N/mm has been connected on the opposite side of to the comparator. The movements formed by the effect of the friction force have been measured by this method.
2
Al
1.5
Al-AlO
1
Al-SiC Al-ALOSiC
0.5 0 0
0.5
1
1.5
2
2.5
Time (h) Hardness values are shown in Table 2. Surface roughness values before and after wear are shown in Table 3. Surface roughness
Fig. 4. The wear losses of bearing-time variation Al composite bearings.
2
3
4 5 7
1
6
8
Fig. 1. Radial journal bearing wear test rig: 1. Comparator, 2. Rigid bar, 3. Load contact point (rolling bearing), 4. Journal sample, 5. Journal bearing samples, 6. Plate bar, 7. Motor and 8. Loads.
B.S. Ünlü, E. Atik / Materials and Design 30 (2009) 1381–1385
Wear Loss (mg)
8
Al Al-AlO Al-SiC Al-ALOSiC
6 4 2 0 0
0.5
1
1.5
2
2.5
Time (h)
3
Wear Rate (Wr)x10-6[mm /Nm]
Fig. 5. The wear losses of journal-time variation Al composite bearings.
8 7 6 5 4 3 2 1 0 Al
Al-Al2O3
Al-SiC
1383
2–6. The highest friction coefficient and journal weight loss occurred in pure Al bearing. The lowest friction coefficient, bearing and journal weight loss occurred in particle reinforced Al bearings. The highest bearing and journal weight loss occurred for pure Al bearing. From these bearings, wear loss of pure Al approximately was 2.5 mg, loss of particle reinforced Al bearings was 0.5 mg in 2.5 h. Journal weight loss for pure Al was 8 mg and that for particle reinforced Al bearings were about 0.8 mg. Bearing wear rate of pure Al was 6.7 10 6 [mm3/Nm], and that for particle reinforced Al bearings was (1.64–1.89) 10 6 [mm3/Nm]. So, bearing wear resistance increased about 4–5 times and journal wear resistance increased about 10 times. Bai et al. [2], Nesarikar et al. [4], Prasad [5], Lim et al. [7], Liu and Ogi [9], Prasad and Rohatgi [13], Prasad et al. [14], S ß ahin [21,22], Reihani [23], Zhiqiang et al. [24], and Yalçın and Akbulut [25] investigated wear properties of particle reinforced Al composites on pin-on-disc wear dry test conditions. In these studies, they reported that the wear rate increased with increasing applied load and sliding distance, and wear and hardness properties increased with increasing particle reinforcement. These studies were carried out on pin-on-disc wear dry test conditions. But, there is not any study on radial journal bearing wear test rig under lubricated conditions.
Al-AlOSiC
Bearing Materials Fig. 6. The compare of wear rates bearing materials.
values decreased in particle reinforced bearings after wear tests. As particle quantity adding, hardness increased. Atik [3], Prasad et al. [6], Sßahin [21] and Reihani [25] reported that hardness properties increased with adding particle reinforcement. In our study, similar results were obtained. Hardness and roughness properties improved because of particle reinforcement. 3.2. Wear properties Friction coefficient, bearing temperature, bearing and journal weight loss values, and bearing wear rates are shown in Figs.
3.3. Physical and chemical properties The wear surfaces in the specimens have been measured using the optical (Hund Wetzlar CCD-290) and scanning electron microscope (Jeol JSM-6060). Less adhesive wear tracks have occurred for particle reinforced Al composite bearings, due to particle adding and better wear resistance property (Fig. 7b–d), as compared to pure Al bearing (Fig. 7a). When physical and chemical properties of samples have been examined at scanning electron microscope (SEM) (Fig. 8), adhesive wear tracks and torn particles can be clearly seen in pure Al bearing (Fig. 8a). These adhesive wear tracks and torn particles which sinked to matrix surface have not formed in particle reinforced Al composite bearings (Fig. 8b–d). Reihani [23], Zhiqiang et al. [24], and Yalçın and Akbulut [25] investigated wear surfaces in particle reinforced Al composites.
Fig. 7. Microstructure of wear surfaces (a) Al, (b) Al–Al2O3, (c) Al–SiC and (d) Al–Al2O3–SiC.
1384
B.S. Ünlü, E. Atik / Materials and Design 30 (2009) 1381–1385
Fig. 8. SEM microstructure of wear surfaces (a) Al, (b) Al–Al2O3, (c) Al–SiC and (d) Al–Al2O3–SiC.
They observed that particles are uniformly distributed in the matrix and observed abrasion wear, delamination and huge wear tracks on the wear surfaces. 4. Conclusions We conclude that journal bearings manufactured from particle reinforced Al composite materials may be effectively used in the industry due to better tribological properties. In this study, tribological properties of journal bearings manufactured by particle reinforced Al composite materials were investigated. Consequently, tribological properties of particle reinforced Al composite bearings have been improved by these methods. Based on the findings our study, the following conclusions can be drawn: 1. Surface roughness values decreased in particle reinforced bearings after wear tests. 2. Hardness values increased with adding particle reinforcement in bearings. 3. Friction coefficient of particle reinforced Al composite bearings values decreased more than that of pure Al bearing. 4. Bearing temperatures of particle reinforced samples decreased about 3–4 °C. 5. Wear loss of particle reinforced Al composite bearings decreased about 5 times and wear loss of journal decreased about 10 times than that of pure Al bearing. 6. Wear rate of particle reinforced Al composite bearings decreased about 4–5 times. So, bearing wear resistance increased about 4–5 times and journal wear resistance increased about 10 times. 7. When wear surfaces of samples were examined at optical and scanning electron microscope wear surfaces of pure Al bearing samples were rougher than those of particle reinforced Al bearings samples. Adhesive wear tracks have decreased for particle reinforced Al composite bearings, due to particle adding and better wear resistance property. Due to their lower particle
addition, these particle reinforced bearings have shown same behavior as base material. This situation is important for less bearing and journal wear.
References [1] Gahr KH, Schneider J. Surface modification of ceramics for improved tribological properties. Ceram Int 2000;26:363–70. [2] Bai M, Xue Q, Wang X, Wan Y, Liu W. Wear mechanism of SiC whiskerreinforced 2024 aluminum alloy matrix composites in oscillating sliding wear tests. Wear 1995;185:197–202. [3] Atik E. Determination of manufacturing conditions and optimum mechanical properties on age able Al–Al2O3 composite for wear resist. PhD thesis, Uludag˘ University, Bursa, Turkey; 1994 [in Turkish]. [4] Nesarikar AR, Tewari SN, Graham EE. Room temperature wear characteristics of Al2O3 – particle reinforced aluminum alloy composite. Mater Sci Eng 1991;147:191–9. [5] Prasad BK. Dry sliding wear response of some bearing alloys as influenced by the nature of micro constituents and sliding conditions. Metall Trans A 1998;28:809–15. [6] Prasad BK, Vankatesworlu K, Jhu AK, Modi OP, Das S, Dasgupta R, et al. Sliding wear response of an Al–Cu alloy: the influence of SiC particle reinforcement and test parameters. J Mater Sci Lett 1998;17:1121–3. [7] Lim SC, Gupta M, Ren L, Kwok JKM. The tribological properties of Al–Cu/SiCP metal–matrix composites fabricated using the rheocasting technique. J Mater Proc Technol 1999;89–90:591–6. [8] Moustafa SF, Soliman FA. Wear resistance of d-type alumina fiber reinforced Al-4% Cu matrix composite. Tribol Lett 1997;3:311–5. [9] Liu HN, Ogi K. Dry sliding wear of an Al2O3 continuous fiber reinforced Al–Cu Alloy against steel counter face. J Mater Sci 1999;34:5593–9. [10] Lepper K, James Chashechkina MJ, Rigney DA. Sliding behavior of selected aluminum alloy. Wear 1997;203–204:46–56. [11] Niinomi M, Fukunaga K, Takeda J. Friction wear of commercial aluminum alloys. Mater Sci Forum 1997;331–337:1519–24. [12] Haque MM, Sharif A. Study on wear properties of aluminum–silicon piston alloy. J Mater Proc Technol 2001;118:69–73. [13] Prasad SV, Rohatgi PK. Tribological properties of Al alloy particle composites. J Metals 1987:22–6. [14] Prasad BK, Vankatesworlu K, Modi OP, Jha AK, Das S, Dasgupta R, et al. The effects of primary silicon particles on the sliding wear behavior of aluminum– silicon alloys. J Mater Sci Lett 1998;17:1381–3. [15] Liu YL, Kang SB, Kim HW. The complex microstructures in an as-cast Al–Mg–Si alloy. Mater Lett 1999(41):267–72. [16] Gürler R. Sliding wear behavior of a silicon carbide particle-reinforced aluminum–magnesium alloy. J Mater Sci Lett 1999;18:553–4.
B.S. Ünlü, E. Atik / Materials and Design 30 (2009) 1381–1385 [17] Ünlü BS. Determination of usability of boronized ferrous based materials as bearing and tribological properties in Journal bearings. PhD thesis, Celal Bayar University, Manisa, Turkey; 2004 [in Turkish]. [18] Sharma SC, Satish BM, Girish BM, Somashekar DR. Wear characteristics of phosphor-bronze/silicon carbide particulate composites. J Mater Proc Technol 2001:65–8. [19] Atik E, Ünlü BS, Meriç C. Design of radial journal bearing wear test rig. In: Conf mach mater technol, Manisa, Turkey; 2001. p. 98–103 [in Turkish]. [20] Ünlü BS, Atik E. Determination of friction coefficient in journal bearings. Mater Des 2007;28:973–7.
1385
[21] S ß ahin Y. The mechanical and wear behavior of metal matrix composites. PhD thesis, UK: Aston University in Birmingham; 1994. [22] S ß ahin Y. Wear behavior of aluminum alloy and its composites reinforced by SiC particles using statistical analysis. Mater Des 2003;24:95–103. [23] Reihani SMS. Processing of squeeze cast Al6061-30 vol% SiC composites and their characterization. Mater Des 2006;27:216–22. [24] Zhiqiang S, Di Z, Guobin L. Evaluation of dry sliding wear behavior of silicon particles reinforced aluminum matrix composites. Mater Des 2005;26:454–8. [25] Yalcin Y, Akbulut H. Dry wear properties of A356-SiC particle reinforced MMCs produced by two melting routes. Mater Des 2006;27:872–81.
Contents lists available at ScienceDirect
Materials and Design journal homepage: www.elsevier.com/locate/matdes
Short Communication
Tribological properties of journal bearings manufactured from particle reinforced Al composites Bekir Sadık Ünlü a,*, Enver Atik b,1 a b
Celal Bayar University, Vocational High School, Department of Machinery, 45400-Turgutlu-Manisa, Turkey Celal Bayar University, Engineering Faculty, Department of Mechanical Engineering, 45140-Muradiye-Manisa, Turkey
a r t i c l e
i n f o
Article history: Received 21 April 2008 Accepted 30 June 2008 Available online 15 July 2008
a b s t r a c t In this study, journal bearings were manufactured from composite structures by casting method reinforcing 3% (Al2O3 and SiC) and (3% Al2O3 + 3% SiC) into pure Al. Tribological properties of these bearings were investigated by wear experiments at lubricated conditions under 20 N load and 1500 rpm on the radial journal bearing wear test rig. Effects of these composites on wear properties were investigated. Consequently, tribological properties of these particle reinforced composite bearings have significantly improved. In addition, particle reinforced Al composites were used to produce journal bearing. Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction Metal matrix composites (MMCs) are obtained by adding hard particles such as Al2O3 and SiC into Al alloys to have good mechanical properties. These composites are used as cutting tools, bearing parts, and medical rigs. Many methods were developed to add these particles into pure Al [1,2]. There have been a lot of studies dealing with application problems of these methods [3]. Seramic reinforced Al alloys are used due to their good wear resistance and low density in automotive industry [4]. Yield strength of Al–Cu alloys decrease by adding SiC but their hardness and sliding properties increase. Tribological properties of these materials are higher than those of Al–SiC [5–7]. In addition, Al–Al2O3 composites having good mechanical and tribological properties are used in crank bearings and motor blocks in order to improve wear resistance [8,9]. Al alloys containing Cu, Mg, Si, and Sn are used as bearing materials [10]. Until the early 1940’s, white metal was used and then Al alloys were used as bearing materials [11]. Al alloys can be used in environments where corrosion is a problem. Wear resistance of Si added Al alloys is higher than those of the other Al alloys [12]. Al–Si alloys have good castability, thermal conductivity, and weldability, high strength and excellent corrosion resistance. They are used in pistons and bearings due to these properties. Si particles can be distributed into structure uniformly, thus material hardness increases [13,14]. In addition, Al–Mg–Si alloys are used due to excellent sliding properties in tribology applications. These
* Corresponding author. Tel.: +90 2363124888; fax: +90 2363144566. E-mail addresses: [email protected] (B.S. Ünlü), [email protected] (E. Atik). 1 Tel.: +90 2362412144; fax: +90 2362412143. 0261-3069/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.matdes.2008.06.069
properties are high strength, high deformability and good wear resistance [15]. Finally, particle reinforcements may also be added to Al–Mg alloys. These alloys have low strength because of high heat friction. These properties are improved by adding SiC [16]. Therefore; these particle reinforced composites may be used as journal bearing material [17]. These metal matrix composites are used in journal bearing, piston, cylinder and aircraft brake applications. The tribological properties of these materials are improved by adding SiC [18]. In this study, tribological properties of journal bearings manufactured from composite structures by casting method pure Al, particle reinforced, 3% (Al2O3 and SiC), and (3% Al2O3 + 3% SiC) were investigated. 2. Experimental studies 2.1. Preparation of experimental materials In this study, pure Al (99% purity), Al based (3% Al2O3 and SiC, and 3% Al2O3 + 3% SiC) particle reinforced materials have been used as journal bearing and SAE 1050 material as shaft (journal). The chemical compositions of the materials used in the experiments were given in Table 1. Dimensions of bearing specimens were as follows: inner diameter (d = 10+0.05 mm), width (B = 10 mm), outer diameter (D = 15 mm). The specimens have been worn and friction coefficient have been measured at radial journal bearing wear test rig at lubricated condition according to the procudure by Atik et al. [19] and Ünlü and Atik [20]. The wear losses have been measured on lubricated conditions of 20 N loads, 1500 rpm (v = 0.785 m/s velocity) and every 30 min for 2.5 h (7065 m sliding distance). Lubricating has been done by SAE 90 gear oil. The specimens were cleaned. The microstructures of wear surfaces have been photographed using
1382
B.S. Ünlü, E. Atik / Materials and Design 30 (2009) 1381–1385
Table 1 Chemical composition of journal material (wt.%)
Table 3 Surface roughness of bearing materials
Material
C
Si
Mn
P
S
Fe
Roughness (lm)
Al
Al–Al2O3
Al–SiC
Al–Al2O3–SiC
SAE 1050
0.51
0.3
0.7
0.04
0.05
Balance
Before wear After wear
3.16 4.92
2.34 2.91
0.65 0.72
1.12 1.24
Materials
Al
Al–Al2O3
Al–SiC
Al–Al2O3–SiC
Hardness (HB)
40
66
62
63
optical and scanning electron microscope. In addition, hardness has been measured using a macrotester type (Table 2). Surface roughness tests have been performed on Mitutoyo-CE surface roughness test rig.
Friction Coefficient (μ)
Table 2 Hardness of bearing materials
0.08
Al
0.06
Al-AlO 0.04
Al-SiC
0.02
Al-ALOSiC
0 0
0.5
1
1.5
2
2.5
Time (h) 2.2. Radial journal bearing wear test rig
3.1. Hardness and surface roughness properties
45
Al 40
Al-AlO Al-SiC
35
Al-ALOSiC 30 0
0.5
1
1.5
2
2.5
Time (h) Fig. 3. The bearing temperature–time variation Al composite bearings.
2.5
Wear Loss (mg)
3. Results and discussion
Temperature (ºC)
Fig. 2. The friction coefficient-time variation Al composite bearings.
Bearings materials in journal bearings are generally selected from materials which have lower wear strength than the shaft material, thereby lowering the wearing of the shaft significantly. For this reason, journal bearing wear test apparatus are designed to examine the wearing of bearing materials. In this study, a special bearing wear test apparatus has been designed to examine the wearing behavior of bearing material and the shaft together. Therefore, it is possible to investigate different bearing and shaft materials and the effects of heat treatments on these materials. Such a mechanism provides wear of bearings rather than using standard methods as this is more appropriate direct [19]. The system is formed by a weight applied by a rigid bar, a steel bar connected to the bearing from a distance and a comparator. Friction coefficient is determined from the friction force formed along the rotating direction of the bearing and from the movement of the steel bar connected to the bearing [20]. Radial wear test rig is illustrated in Fig. 1. In the experiments under lubricated conditions, very little movement was taken place for high comparator’s spring coefficient and low friction. Therefore, a tensile spring of k = 0.004 N/mm has been connected on the opposite side of to the comparator. The movements formed by the effect of the friction force have been measured by this method.
2
Al
1.5
Al-AlO
1
Al-SiC Al-ALOSiC
0.5 0 0
0.5
1
1.5
2
2.5
Time (h) Hardness values are shown in Table 2. Surface roughness values before and after wear are shown in Table 3. Surface roughness
Fig. 4. The wear losses of bearing-time variation Al composite bearings.
2
3
4 5 7
1
6
8
Fig. 1. Radial journal bearing wear test rig: 1. Comparator, 2. Rigid bar, 3. Load contact point (rolling bearing), 4. Journal sample, 5. Journal bearing samples, 6. Plate bar, 7. Motor and 8. Loads.
B.S. Ünlü, E. Atik / Materials and Design 30 (2009) 1381–1385
Wear Loss (mg)
8
Al Al-AlO Al-SiC Al-ALOSiC
6 4 2 0 0
0.5
1
1.5
2
2.5
Time (h)
3
Wear Rate (Wr)x10-6[mm /Nm]
Fig. 5. The wear losses of journal-time variation Al composite bearings.
8 7 6 5 4 3 2 1 0 Al
Al-Al2O3
Al-SiC
1383
2–6. The highest friction coefficient and journal weight loss occurred in pure Al bearing. The lowest friction coefficient, bearing and journal weight loss occurred in particle reinforced Al bearings. The highest bearing and journal weight loss occurred for pure Al bearing. From these bearings, wear loss of pure Al approximately was 2.5 mg, loss of particle reinforced Al bearings was 0.5 mg in 2.5 h. Journal weight loss for pure Al was 8 mg and that for particle reinforced Al bearings were about 0.8 mg. Bearing wear rate of pure Al was 6.7 10 6 [mm3/Nm], and that for particle reinforced Al bearings was (1.64–1.89) 10 6 [mm3/Nm]. So, bearing wear resistance increased about 4–5 times and journal wear resistance increased about 10 times. Bai et al. [2], Nesarikar et al. [4], Prasad [5], Lim et al. [7], Liu and Ogi [9], Prasad and Rohatgi [13], Prasad et al. [14], S ß ahin [21,22], Reihani [23], Zhiqiang et al. [24], and Yalçın and Akbulut [25] investigated wear properties of particle reinforced Al composites on pin-on-disc wear dry test conditions. In these studies, they reported that the wear rate increased with increasing applied load and sliding distance, and wear and hardness properties increased with increasing particle reinforcement. These studies were carried out on pin-on-disc wear dry test conditions. But, there is not any study on radial journal bearing wear test rig under lubricated conditions.
Al-AlOSiC
Bearing Materials Fig. 6. The compare of wear rates bearing materials.
values decreased in particle reinforced bearings after wear tests. As particle quantity adding, hardness increased. Atik [3], Prasad et al. [6], Sßahin [21] and Reihani [25] reported that hardness properties increased with adding particle reinforcement. In our study, similar results were obtained. Hardness and roughness properties improved because of particle reinforcement. 3.2. Wear properties Friction coefficient, bearing temperature, bearing and journal weight loss values, and bearing wear rates are shown in Figs.
3.3. Physical and chemical properties The wear surfaces in the specimens have been measured using the optical (Hund Wetzlar CCD-290) and scanning electron microscope (Jeol JSM-6060). Less adhesive wear tracks have occurred for particle reinforced Al composite bearings, due to particle adding and better wear resistance property (Fig. 7b–d), as compared to pure Al bearing (Fig. 7a). When physical and chemical properties of samples have been examined at scanning electron microscope (SEM) (Fig. 8), adhesive wear tracks and torn particles can be clearly seen in pure Al bearing (Fig. 8a). These adhesive wear tracks and torn particles which sinked to matrix surface have not formed in particle reinforced Al composite bearings (Fig. 8b–d). Reihani [23], Zhiqiang et al. [24], and Yalçın and Akbulut [25] investigated wear surfaces in particle reinforced Al composites.
Fig. 7. Microstructure of wear surfaces (a) Al, (b) Al–Al2O3, (c) Al–SiC and (d) Al–Al2O3–SiC.
1384
B.S. Ünlü, E. Atik / Materials and Design 30 (2009) 1381–1385
Fig. 8. SEM microstructure of wear surfaces (a) Al, (b) Al–Al2O3, (c) Al–SiC and (d) Al–Al2O3–SiC.
They observed that particles are uniformly distributed in the matrix and observed abrasion wear, delamination and huge wear tracks on the wear surfaces. 4. Conclusions We conclude that journal bearings manufactured from particle reinforced Al composite materials may be effectively used in the industry due to better tribological properties. In this study, tribological properties of journal bearings manufactured by particle reinforced Al composite materials were investigated. Consequently, tribological properties of particle reinforced Al composite bearings have been improved by these methods. Based on the findings our study, the following conclusions can be drawn: 1. Surface roughness values decreased in particle reinforced bearings after wear tests. 2. Hardness values increased with adding particle reinforcement in bearings. 3. Friction coefficient of particle reinforced Al composite bearings values decreased more than that of pure Al bearing. 4. Bearing temperatures of particle reinforced samples decreased about 3–4 °C. 5. Wear loss of particle reinforced Al composite bearings decreased about 5 times and wear loss of journal decreased about 10 times than that of pure Al bearing. 6. Wear rate of particle reinforced Al composite bearings decreased about 4–5 times. So, bearing wear resistance increased about 4–5 times and journal wear resistance increased about 10 times. 7. When wear surfaces of samples were examined at optical and scanning electron microscope wear surfaces of pure Al bearing samples were rougher than those of particle reinforced Al bearings samples. Adhesive wear tracks have decreased for particle reinforced Al composite bearings, due to particle adding and better wear resistance property. Due to their lower particle
addition, these particle reinforced bearings have shown same behavior as base material. This situation is important for less bearing and journal wear.
References [1] Gahr KH, Schneider J. Surface modification of ceramics for improved tribological properties. Ceram Int 2000;26:363–70. [2] Bai M, Xue Q, Wang X, Wan Y, Liu W. Wear mechanism of SiC whiskerreinforced 2024 aluminum alloy matrix composites in oscillating sliding wear tests. Wear 1995;185:197–202. [3] Atik E. Determination of manufacturing conditions and optimum mechanical properties on age able Al–Al2O3 composite for wear resist. PhD thesis, Uludag˘ University, Bursa, Turkey; 1994 [in Turkish]. [4] Nesarikar AR, Tewari SN, Graham EE. Room temperature wear characteristics of Al2O3 – particle reinforced aluminum alloy composite. Mater Sci Eng 1991;147:191–9. [5] Prasad BK. Dry sliding wear response of some bearing alloys as influenced by the nature of micro constituents and sliding conditions. Metall Trans A 1998;28:809–15. [6] Prasad BK, Vankatesworlu K, Jhu AK, Modi OP, Das S, Dasgupta R, et al. Sliding wear response of an Al–Cu alloy: the influence of SiC particle reinforcement and test parameters. J Mater Sci Lett 1998;17:1121–3. [7] Lim SC, Gupta M, Ren L, Kwok JKM. The tribological properties of Al–Cu/SiCP metal–matrix composites fabricated using the rheocasting technique. J Mater Proc Technol 1999;89–90:591–6. [8] Moustafa SF, Soliman FA. Wear resistance of d-type alumina fiber reinforced Al-4% Cu matrix composite. Tribol Lett 1997;3:311–5. [9] Liu HN, Ogi K. Dry sliding wear of an Al2O3 continuous fiber reinforced Al–Cu Alloy against steel counter face. J Mater Sci 1999;34:5593–9. [10] Lepper K, James Chashechkina MJ, Rigney DA. Sliding behavior of selected aluminum alloy. Wear 1997;203–204:46–56. [11] Niinomi M, Fukunaga K, Takeda J. Friction wear of commercial aluminum alloys. Mater Sci Forum 1997;331–337:1519–24. [12] Haque MM, Sharif A. Study on wear properties of aluminum–silicon piston alloy. J Mater Proc Technol 2001;118:69–73. [13] Prasad SV, Rohatgi PK. Tribological properties of Al alloy particle composites. J Metals 1987:22–6. [14] Prasad BK, Vankatesworlu K, Modi OP, Jha AK, Das S, Dasgupta R, et al. The effects of primary silicon particles on the sliding wear behavior of aluminum– silicon alloys. J Mater Sci Lett 1998;17:1381–3. [15] Liu YL, Kang SB, Kim HW. The complex microstructures in an as-cast Al–Mg–Si alloy. Mater Lett 1999(41):267–72. [16] Gürler R. Sliding wear behavior of a silicon carbide particle-reinforced aluminum–magnesium alloy. J Mater Sci Lett 1999;18:553–4.
B.S. Ünlü, E. Atik / Materials and Design 30 (2009) 1381–1385 [17] Ünlü BS. Determination of usability of boronized ferrous based materials as bearing and tribological properties in Journal bearings. PhD thesis, Celal Bayar University, Manisa, Turkey; 2004 [in Turkish]. [18] Sharma SC, Satish BM, Girish BM, Somashekar DR. Wear characteristics of phosphor-bronze/silicon carbide particulate composites. J Mater Proc Technol 2001:65–8. [19] Atik E, Ünlü BS, Meriç C. Design of radial journal bearing wear test rig. In: Conf mach mater technol, Manisa, Turkey; 2001. p. 98–103 [in Turkish]. [20] Ünlü BS, Atik E. Determination of friction coefficient in journal bearings. Mater Des 2007;28:973–7.
1385
[21] S ß ahin Y. The mechanical and wear behavior of metal matrix composites. PhD thesis, UK: Aston University in Birmingham; 1994. [22] S ß ahin Y. Wear behavior of aluminum alloy and its composites reinforced by SiC particles using statistical analysis. Mater Des 2003;24:95–103. [23] Reihani SMS. Processing of squeeze cast Al6061-30 vol% SiC composites and their characterization. Mater Des 2006;27:216–22. [24] Zhiqiang S, Di Z, Guobin L. Evaluation of dry sliding wear behavior of silicon particles reinforced aluminum matrix composites. Mater Des 2005;26:454–8. [25] Yalcin Y, Akbulut H. Dry wear properties of A356-SiC particle reinforced MMCs produced by two melting routes. Mater Des 2006;27:872–81.