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Influence of Mn Content on Tribological Wear Behaviour of ZA-27 Alloy
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 4 (2017) 10927–10934
www.materialstoday.com/proceedings
AMMMT 2016
Influence of Mn Content on Tribological Wear Behaviour of ZA-27 Alloy Veerabhadrappa Algura*, V R Kabadib, Ganechari S Mc, Vithal Rao Chavand a*
Department of Industrial & Production Engineering, Rao Bahadur Y Mahabaleshwarappa Engineering College, Ballari, 583104, India. b Department of Mechanical Engineering, Nitte Meenakshi Institute of Technology Yelahanka, Bengaluru, 560064, India. c Department of Mechanical Engineering, Thakur Polytechnic, Kandivali (E), Mumbai, 400 101, India. d Department of Mechanical Engineering, Rao Bahadur Y Mahabaleshwarappa Engineering College, Ballari, 583104, India.
Abstract The impact of Mn content on tribological wear behaviour of ZA-27 alloy which is used in an Industrial engineering and tribological applications has been studied. Wear test were conducted under the operational conditions of varying in Nr. pressures and sliding speeds using pin-on-disc wear testing machine. To peruse the wear mechanisms of worn out surface of samples were investigate by SEM images. Result shows 1.5 m/s sliding speed and 0.2498 MPa is observed as critical sliding speed and critical Nr. pressure. Also, minimum vol. wear rate and frictional force for 0.5% Mn content ZA-27 alloy. Laminative wear mechanism for 0.2% Mn, three body wear mechanism for 0.5% Mn and abrasive wear mechanism for 1% Mn is observed. © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of Advanced Materials, Manufacturing, Management and Thermal Science (AMMMT 2016). Keywords: ZA-27 alloy; Debris;SEM; Wear mechanism.
1. Introduction The results of extensive research have been developed on number of zinc-based ternary and quaternary alloys [1]. From several decades ZA alloys became more important material at engineering and tribological applications [2]. The origin of zinc-aluminium (ZA) alloys were established since 1950-1970, among the origin of ZA, ZA-12 was developed during 1950s, while ZA-8 and ZA-27 were aged in late 1970s [3]. In engineering application, the loss of material is unavoidable due to wear. To overcome this problem many searches have been carried out for developing new wear resistance materials without compromising the functional requirements [4]. *Corresponding author. Tel.: +918867168410 E-mail address: [email protected] 2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of Advanced Materials, Manufacturing, Management and Thermal Science (AMMMT 2016).
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Veerabhadrappa Algur/ Materials Today: Proceedings 4 (2017) 10927–10934
Nomenclature SEM Nr. vol.
Scanning Electron Microscope Normal volumetric
Zinc based alloys have been considered as a competing material to replace numerous ferrous and non-ferrous alloys [6]. By adding aluminium in zinc, enhances the smoothness and castability of the molten ZA metal. By adding small amount of magnesium it prevents intergranular attack because of impurities present. Copper is added to minimize the effects of impurities and retained strength & hardness due to its high thermal conductivity. Silicon is integrated to improve the hardness and strength of alloy [7]. ZA alloys are applicable for various casting methods. These alloys exhibit mechanical characterization equal to those of aluminium and cast iron alloys. Moreover, they have low-cost, energy-preserving melting, excellent castability, and comparable or frequently predominant bearing and wear properties. The bearings and wear characteristics which are produced from ZA alloys are used for bushbearings, flanges and particularly used in mining, milling machines, earthmoving equipments and cable winches. A zinc aluminium alloy replaces the bronzes due to its cost and energy effective in various sliding applications [8]. One of the major constraints of typical zinc-aluminium alloys, containing 8-27% Al is decay of their creep strength, wear resistance and mechanical inheritance at higher temperatures (above 1000C) and their dimensional uncertainty [6]. An important aspect of ZA alloys is great castability and rare combination of properties, have become substitute mainly for aluminium alloys, bearing bronzes, cast iron, steels & plastic fabrication [4,7]. Many researches are added different alloys like Cu, Si, Sr, Ni, Mn etc., to improve the tribological properties. When zincaluminium alloy is undergone heat treatment, it reduces the problem of dimensional instability [9]. The purpose of this research is to understand the influence of Mn content on tribological wear behaviour in ZA-27 alloy. 2. Experimental details 2.1. Sample preparations The composition of experimental alloys in weight percent was predicted on ZA-27 alloy. A series of alloys with varying Mn substance were set up by gravity die casting. Compositions of the experimental alloys are catalogued in Table 1 were assessed using atomic absorption spectrometer. Melting was made in crucible furnace at 700ºC and poured into the sand moulds, which are preheated to relatively 1500C in atmospheric air. 2.2. Hardness test details The hardness test was carried out on each alloy at an applied load of 613 N, ball Indentor of diameter 2.5 mm under a dwell time of 4 seconds using Brinell hardness test as laid out in Table 1. 2.3. Wear test details Sliding wear tests were led on a pin-on-disc wear testing machine (as per ASTM : G99-25) under different load up to 40 N and different sliding speed up to 2.5 m/s against EN31 steel disc having hardness HRc 61. The samples of pin were 10 mm in diameter and 33 mm long. The pin sample surfaces and the steel disc were ground utilizing emery paper before every test. Common track radius of 70 mm and keeping a nailed sliding distance of 2500 m is used to analysis the samples. Prior each test the disc was cleaned with natural solvents to abstract contaminants. The wear losses of sample are weighed utilizing an electronic microbalance (±0.0001g). The wear rate was computed by weight-loss method. Later volume loss was estimated by considering its density. By adopting SEM, wear surfaces and debris of selected samples were characterized.
Veerabhadrappa Algur/ Materials Today: Proceedings 4 (2017) 10927–10934
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Table 1 The Chemical composition of ZA-27 alloy Sample
Composition (wt%)
Brinell Hardness
Al
Cu
Mg
Si
Mn
Zn.
(HB)
M1
27.42
2.05
0.039
3.54
0.17
Balance
69.46
M2
27.37
2.08
0.039
3.64
0.54
Balance
81.86
M3
27.98
2.04
0.038
3.48
0.98
Balance
98.2
3. Result and discussion 3.1. Wear studies Effect of five Nr. pressures and sliding speeds on vol. wear rate is shown in Fig. 1 and Frictional force in Fig. 2. The graphs have been plotted for 0.2, 0.5 and 1% Mn on ZA-27 alloy to explain the wear behavior. The general trend of vol. wear rate is reduced with increasing in sliding speed, because of reduction in contact area of asperity. Also it is observed that with further increment in the sliding speed under the same Nr. pressure the vol. wear rate is enhanced. During wearing, the wearing surface deforms plastically and becomes hard due to strain hardening. Hence, increase in hardness of the wearing surface. As per Archard’s equation, volume loss is inversely proportional to the hardness. During wearing, wearing surface becomes hot due to the friction between wearing pin and sliding disc. This frictional temperature will increase with the sliding speed and Nr. pressure. This increase in Nr. pressure and sliding speed, frictional temperature as well as surface hardness will increase. Surface hardness will increase until frictional temperature reaches the recrystallization temperature of the specimen. Once this temperature reaches then plastic deformation of the wearing surface can be considered as hot working process. During hot working process hardness will not increase but may reduce with further increase in the frictional temperature. Fig. 1 shows an increase in the Nr. pressure i.e. Fig. (a) for 0.0624 MPa, Fig. (b) for 0.1249 MPa, Fig. (c) for 0.2498 MPa, Fig. (d) for 0.3747 MPa and Fig. (e) for 0.4996 MPa, the vol. wear rate values are lifted up. This is because of increment in the number of asperities and asperity contact area. But values of vol. wear rate for the Nr. pressure of 0.2498 MPa, Fig. 1(c), is low when compared with the vol. wear rate of other Nr. pressures. Further it is noticed that minimum variation in vol. wear rate values are observed among the different samples and sliding speeds. Hence, 0.2498 MPa can be considered as a critical Nr. pressure where under this Nr. pressure, vol. wear rate of all samples and sliding speeds is low. It is also noticed from Fig. 1, with increment in the sliding speed the general trend of vol. wear rate is decreased for all Nr. pressures and samples, due to the reduction in growth of micro weld also reduction in residential time between the wearing surfaces. From the Fig. 1(a), vol. wear rate at the sliding speed of 1.5 m/s is minimum and same for all samples. This is almost true for other Nr. pressures also. Hence, this can be considered as a critical sliding speed. Manganese is a hard and brittle material. It has a high work hardening capacity material. As it deforms, material becomes hard and brittle. With increment in the volume fraction of Mn in the ZA-27 alloy, the corresponding hardness is increased (Table 1). With increment in the hardness, the wear loss will decrease as per Archard equation. But it doesn’t mean that with increase in the hardness the volume loss will decrease, because with increase in the hardness, the material becomes brittle. As the brittleness of the material increases, its corresponding shear strength is reduced results in increase in volume loss. During wearing, separation of material in the form of debris depends upon the shear strength of the material. It is noticed (Fig. 1) that vol. wear rate of 0.5% Mn has shown minimum values when compared with the other samples for all the Nr. pressures. On the other hand, maximum vol. wear rate is obtained for 1% Mn, due to its brittleness.
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Fig. 1. Response of sliding speed on vol. wear rate for distinct samples.
Veerabhadrappa Algur/ Materials Today: Proceedings 4 (2017) 10927–10934
Fig. 2. Response of sliding speed on frictional force for distinct samples.
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From the Fig. 2 it is noticed, frictional force is decremented with increment in the sliding speed and lifted up with increment in the Nr. pressure. With increase in the Nr. pressure, total area of contact between the rubbing surfaces will increase. This results in increment in the frictional force. With increment in the sliding speed the total area of contact will decrease this result in reduction in frictional force. Also it is recognized that, at the sliding speed of 1.5 m/s for all the Nr. pressures and samples, the frictional force is low and the corresponding vol. wear rate is also minimum. 3.2. Worn-out and wear debris studies SEM micrograph of worn out surface and wear debris has shown in Fig. 3 and Fig. 4 respectively. These micrographs are for the sliding speed of 2.5 m/s and Nr. pressure of 0.4996 MPa. Fig. 3(a) for 0.2% Mn, Fig. 3(b) for 0.5% Mn and Fig. 3(c) for 1% Mn, three micrographs are under the same operational conditions but varying in percentage of Mn. 0.2% Mn is a soft material, 0.5% Mn is a moderate material and 1% Mn is hard material. From the Fig. 3(a) it is observed that worn-out surface is deformed plastically more. During wearing grooves will form, burr at the edges of the grove deform plastically overlays and laminates on the wearing surface. Later this laminated surface separates from the parent material in the form of flat debris is shown in Fig. 4(a). From the Fig. 3(b) it is observed that there are discontinuous grooves on the wearing surface. This is for 0.5% Mn alloy specimen which is harder than 0.2% Mn and softer than 1% Mn specimen. The wear debris separates and slide freely between the wearing surfaces as shown in Fig. 4(b). These free wear debris behaves like a free abrasive particle. Hence, discontinuous grooves are formed on the wearing surface and the corresponding wear debris, more number of small size wear debris is found. From the Fig. 3(c) it is observed that there are continuous abrasive grooves on the wearing surface. It is for 1% Mn specimen which is hard. A hard asperity has grooved on the wearing surface. The corresponding hard wear debris is shown in Fig. 4(c).
(a)
(b)
Discontinuous grooves Laminated
(c)
Abrasive grooves
Fig. 3. SEM micro graph of worn-out surfaces at sliding speed of 2.5 m/s and at Nr. Pressure of 0.4996 MPa. (a) 0.2% Mn, (b) 0.5% Mn and (c) 1% Mn samples.
Veerabhadrappa Algur/ Materials Today: Proceedings 4 (2017) 10927–10934
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Abrasive wear is a severe wear therefore 1% Mn samples has shown higher wear rate when compared with the other samples. Three body abrasive wear is not a severe wear. Because free abrasive debris rolls between the rubbing surfaces but not remove the material considerable. Therefore it has shown minimum wear among the samples. This is observed in 0.5% Mn specimen. (a)
(b)
Laminated wear debris
Loose asperity particles
(c)
Abrasive wear debris
Fig. 4. SEM micro graph of wear debris at sliding speed of 2.5 m/s and at Nr. Pressure of 0.4996 MPa. (a) 0.2% Mn, (b) 0.5% Mn and (c) 1% Mn samples
4. Conclusions The observations made in this study suggest that the wear response depends on factors like composition, Nr. pressures and sliding speeds. Moderate addition of Mn into ZA-27 could reduce vol. wear rate. The experimental alloy with Mn content of approximately 0.5% has the least vol. wear rate observed. For all the samples at all sliding speeds, vol. wear rate is increased with increase in the Nr. pressure, further it is decreased with increasing in sliding speed up to 1.5 m/s. Hence, 1.5 m/s Sliding speed can be considered as critical sliding speed for ZA-27 alloy. At this sliding speed variation in vol. wear rate is minimum under different Nr. pressures for all samples. Nr. pressure of 0.2498 MPa is considered as a critical Nr. pressure. Frictional force is increased with increase in the Nr. pressure and sliding speed for all the samples. Reference [1] V Algur, V R Kabadi, Genechari S M and Sharanabasappa ‘Experimental Investigation on Friction Characteristics of Modified ZA-27 Alloy Using Taguchi Technique’. Int. J. Mech. Eng. & Rob. Res. 3 ( 2014) 24-32. [2] Geng Hao-ran, CUI Feng, Tian Xian-fa, Qian Bao-guang, “Processing technique and sliding friction and wear behaviour of TiB2/ZA-27 compostie”, J.Cent. South Univ. Technology, 12( 2005). [3] Zulkuf Balalan, Mehmet Kaplan, “Investigation of the Microstructure and Wear properties of a Cast ZA Alloy”, Int Jour of Sci & Tech., 2 (2007) 75-81.
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Veerabhadrappa Algur/ Materials Today: Proceedings 4 (2017) 10927–10934
[4] V Algur, V R Kabadi, Genechari S M, P.B.Shetty, Poornima H “Analysis of Wear Behaviour of a Heat Treated Modified ZA-27 Alloy by Taguchi Technique”, Int Jour of Rec and Innov Trends, 2 (2014). [5] P. Choudhary, S. Das, B.K. Datta, “Effect of Ni on the wear behaviour of a Zinc-Aluminium alloy”, Journal of Materials Science, 37 (2002) 2103-2107. [6] Hamdullah Cuvalcr, Hasan Bass, “Investigation of the tribological properties of silicon containing zinc-aluminium based journal bearings”, Tribology International, .37 (2004) 433-440. [7] Mario R Rosenberger, Alica E. Ares, Isaura P. Gatti, Carlos E. Schvezov, “Wear resistance of dilute Zn-Al alloys”, Wear, 268 (2010) 15331536. [8] M. Babic, S. Mitrovic, R. Ninkovic, “Tribological potential of Zinc- Aluminium alloys improvement”, Tribology in industry, 31 (2009) 15-27. [9] Mirsolav Babic, Slobodan Mitrovic, Branislav Jeremic, “The influence of heat treatment on the slidiing wear behaviour of a ZA-27 alloy”, Tribology International, 43 (2010) 16-21.
ScienceDirect Materials Today: Proceedings 4 (2017) 10927–10934
www.materialstoday.com/proceedings
AMMMT 2016
Influence of Mn Content on Tribological Wear Behaviour of ZA-27 Alloy Veerabhadrappa Algura*, V R Kabadib, Ganechari S Mc, Vithal Rao Chavand a*
Department of Industrial & Production Engineering, Rao Bahadur Y Mahabaleshwarappa Engineering College, Ballari, 583104, India. b Department of Mechanical Engineering, Nitte Meenakshi Institute of Technology Yelahanka, Bengaluru, 560064, India. c Department of Mechanical Engineering, Thakur Polytechnic, Kandivali (E), Mumbai, 400 101, India. d Department of Mechanical Engineering, Rao Bahadur Y Mahabaleshwarappa Engineering College, Ballari, 583104, India.
Abstract The impact of Mn content on tribological wear behaviour of ZA-27 alloy which is used in an Industrial engineering and tribological applications has been studied. Wear test were conducted under the operational conditions of varying in Nr. pressures and sliding speeds using pin-on-disc wear testing machine. To peruse the wear mechanisms of worn out surface of samples were investigate by SEM images. Result shows 1.5 m/s sliding speed and 0.2498 MPa is observed as critical sliding speed and critical Nr. pressure. Also, minimum vol. wear rate and frictional force for 0.5% Mn content ZA-27 alloy. Laminative wear mechanism for 0.2% Mn, three body wear mechanism for 0.5% Mn and abrasive wear mechanism for 1% Mn is observed. © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of Advanced Materials, Manufacturing, Management and Thermal Science (AMMMT 2016). Keywords: ZA-27 alloy; Debris;SEM; Wear mechanism.
1. Introduction The results of extensive research have been developed on number of zinc-based ternary and quaternary alloys [1]. From several decades ZA alloys became more important material at engineering and tribological applications [2]. The origin of zinc-aluminium (ZA) alloys were established since 1950-1970, among the origin of ZA, ZA-12 was developed during 1950s, while ZA-8 and ZA-27 were aged in late 1970s [3]. In engineering application, the loss of material is unavoidable due to wear. To overcome this problem many searches have been carried out for developing new wear resistance materials without compromising the functional requirements [4]. *Corresponding author. Tel.: +918867168410 E-mail address: [email protected] 2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of Advanced Materials, Manufacturing, Management and Thermal Science (AMMMT 2016).
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Veerabhadrappa Algur/ Materials Today: Proceedings 4 (2017) 10927–10934
Nomenclature SEM Nr. vol.
Scanning Electron Microscope Normal volumetric
Zinc based alloys have been considered as a competing material to replace numerous ferrous and non-ferrous alloys [6]. By adding aluminium in zinc, enhances the smoothness and castability of the molten ZA metal. By adding small amount of magnesium it prevents intergranular attack because of impurities present. Copper is added to minimize the effects of impurities and retained strength & hardness due to its high thermal conductivity. Silicon is integrated to improve the hardness and strength of alloy [7]. ZA alloys are applicable for various casting methods. These alloys exhibit mechanical characterization equal to those of aluminium and cast iron alloys. Moreover, they have low-cost, energy-preserving melting, excellent castability, and comparable or frequently predominant bearing and wear properties. The bearings and wear characteristics which are produced from ZA alloys are used for bushbearings, flanges and particularly used in mining, milling machines, earthmoving equipments and cable winches. A zinc aluminium alloy replaces the bronzes due to its cost and energy effective in various sliding applications [8]. One of the major constraints of typical zinc-aluminium alloys, containing 8-27% Al is decay of their creep strength, wear resistance and mechanical inheritance at higher temperatures (above 1000C) and their dimensional uncertainty [6]. An important aspect of ZA alloys is great castability and rare combination of properties, have become substitute mainly for aluminium alloys, bearing bronzes, cast iron, steels & plastic fabrication [4,7]. Many researches are added different alloys like Cu, Si, Sr, Ni, Mn etc., to improve the tribological properties. When zincaluminium alloy is undergone heat treatment, it reduces the problem of dimensional instability [9]. The purpose of this research is to understand the influence of Mn content on tribological wear behaviour in ZA-27 alloy. 2. Experimental details 2.1. Sample preparations The composition of experimental alloys in weight percent was predicted on ZA-27 alloy. A series of alloys with varying Mn substance were set up by gravity die casting. Compositions of the experimental alloys are catalogued in Table 1 were assessed using atomic absorption spectrometer. Melting was made in crucible furnace at 700ºC and poured into the sand moulds, which are preheated to relatively 1500C in atmospheric air. 2.2. Hardness test details The hardness test was carried out on each alloy at an applied load of 613 N, ball Indentor of diameter 2.5 mm under a dwell time of 4 seconds using Brinell hardness test as laid out in Table 1. 2.3. Wear test details Sliding wear tests were led on a pin-on-disc wear testing machine (as per ASTM : G99-25) under different load up to 40 N and different sliding speed up to 2.5 m/s against EN31 steel disc having hardness HRc 61. The samples of pin were 10 mm in diameter and 33 mm long. The pin sample surfaces and the steel disc were ground utilizing emery paper before every test. Common track radius of 70 mm and keeping a nailed sliding distance of 2500 m is used to analysis the samples. Prior each test the disc was cleaned with natural solvents to abstract contaminants. The wear losses of sample are weighed utilizing an electronic microbalance (±0.0001g). The wear rate was computed by weight-loss method. Later volume loss was estimated by considering its density. By adopting SEM, wear surfaces and debris of selected samples were characterized.
Veerabhadrappa Algur/ Materials Today: Proceedings 4 (2017) 10927–10934
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Table 1 The Chemical composition of ZA-27 alloy Sample
Composition (wt%)
Brinell Hardness
Al
Cu
Mg
Si
Mn
Zn.
(HB)
M1
27.42
2.05
0.039
3.54
0.17
Balance
69.46
M2
27.37
2.08
0.039
3.64
0.54
Balance
81.86
M3
27.98
2.04
0.038
3.48
0.98
Balance
98.2
3. Result and discussion 3.1. Wear studies Effect of five Nr. pressures and sliding speeds on vol. wear rate is shown in Fig. 1 and Frictional force in Fig. 2. The graphs have been plotted for 0.2, 0.5 and 1% Mn on ZA-27 alloy to explain the wear behavior. The general trend of vol. wear rate is reduced with increasing in sliding speed, because of reduction in contact area of asperity. Also it is observed that with further increment in the sliding speed under the same Nr. pressure the vol. wear rate is enhanced. During wearing, the wearing surface deforms plastically and becomes hard due to strain hardening. Hence, increase in hardness of the wearing surface. As per Archard’s equation, volume loss is inversely proportional to the hardness. During wearing, wearing surface becomes hot due to the friction between wearing pin and sliding disc. This frictional temperature will increase with the sliding speed and Nr. pressure. This increase in Nr. pressure and sliding speed, frictional temperature as well as surface hardness will increase. Surface hardness will increase until frictional temperature reaches the recrystallization temperature of the specimen. Once this temperature reaches then plastic deformation of the wearing surface can be considered as hot working process. During hot working process hardness will not increase but may reduce with further increase in the frictional temperature. Fig. 1 shows an increase in the Nr. pressure i.e. Fig. (a) for 0.0624 MPa, Fig. (b) for 0.1249 MPa, Fig. (c) for 0.2498 MPa, Fig. (d) for 0.3747 MPa and Fig. (e) for 0.4996 MPa, the vol. wear rate values are lifted up. This is because of increment in the number of asperities and asperity contact area. But values of vol. wear rate for the Nr. pressure of 0.2498 MPa, Fig. 1(c), is low when compared with the vol. wear rate of other Nr. pressures. Further it is noticed that minimum variation in vol. wear rate values are observed among the different samples and sliding speeds. Hence, 0.2498 MPa can be considered as a critical Nr. pressure where under this Nr. pressure, vol. wear rate of all samples and sliding speeds is low. It is also noticed from Fig. 1, with increment in the sliding speed the general trend of vol. wear rate is decreased for all Nr. pressures and samples, due to the reduction in growth of micro weld also reduction in residential time between the wearing surfaces. From the Fig. 1(a), vol. wear rate at the sliding speed of 1.5 m/s is minimum and same for all samples. This is almost true for other Nr. pressures also. Hence, this can be considered as a critical sliding speed. Manganese is a hard and brittle material. It has a high work hardening capacity material. As it deforms, material becomes hard and brittle. With increment in the volume fraction of Mn in the ZA-27 alloy, the corresponding hardness is increased (Table 1). With increment in the hardness, the wear loss will decrease as per Archard equation. But it doesn’t mean that with increase in the hardness the volume loss will decrease, because with increase in the hardness, the material becomes brittle. As the brittleness of the material increases, its corresponding shear strength is reduced results in increase in volume loss. During wearing, separation of material in the form of debris depends upon the shear strength of the material. It is noticed (Fig. 1) that vol. wear rate of 0.5% Mn has shown minimum values when compared with the other samples for all the Nr. pressures. On the other hand, maximum vol. wear rate is obtained for 1% Mn, due to its brittleness.
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Veerabhadrappa Algur/ Materials Today: Proceedings 4 (2017) 10927–10934
Fig. 1. Response of sliding speed on vol. wear rate for distinct samples.
Veerabhadrappa Algur/ Materials Today: Proceedings 4 (2017) 10927–10934
Fig. 2. Response of sliding speed on frictional force for distinct samples.
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From the Fig. 2 it is noticed, frictional force is decremented with increment in the sliding speed and lifted up with increment in the Nr. pressure. With increase in the Nr. pressure, total area of contact between the rubbing surfaces will increase. This results in increment in the frictional force. With increment in the sliding speed the total area of contact will decrease this result in reduction in frictional force. Also it is recognized that, at the sliding speed of 1.5 m/s for all the Nr. pressures and samples, the frictional force is low and the corresponding vol. wear rate is also minimum. 3.2. Worn-out and wear debris studies SEM micrograph of worn out surface and wear debris has shown in Fig. 3 and Fig. 4 respectively. These micrographs are for the sliding speed of 2.5 m/s and Nr. pressure of 0.4996 MPa. Fig. 3(a) for 0.2% Mn, Fig. 3(b) for 0.5% Mn and Fig. 3(c) for 1% Mn, three micrographs are under the same operational conditions but varying in percentage of Mn. 0.2% Mn is a soft material, 0.5% Mn is a moderate material and 1% Mn is hard material. From the Fig. 3(a) it is observed that worn-out surface is deformed plastically more. During wearing grooves will form, burr at the edges of the grove deform plastically overlays and laminates on the wearing surface. Later this laminated surface separates from the parent material in the form of flat debris is shown in Fig. 4(a). From the Fig. 3(b) it is observed that there are discontinuous grooves on the wearing surface. This is for 0.5% Mn alloy specimen which is harder than 0.2% Mn and softer than 1% Mn specimen. The wear debris separates and slide freely between the wearing surfaces as shown in Fig. 4(b). These free wear debris behaves like a free abrasive particle. Hence, discontinuous grooves are formed on the wearing surface and the corresponding wear debris, more number of small size wear debris is found. From the Fig. 3(c) it is observed that there are continuous abrasive grooves on the wearing surface. It is for 1% Mn specimen which is hard. A hard asperity has grooved on the wearing surface. The corresponding hard wear debris is shown in Fig. 4(c).
(a)
(b)
Discontinuous grooves Laminated
(c)
Abrasive grooves
Fig. 3. SEM micro graph of worn-out surfaces at sliding speed of 2.5 m/s and at Nr. Pressure of 0.4996 MPa. (a) 0.2% Mn, (b) 0.5% Mn and (c) 1% Mn samples.
Veerabhadrappa Algur/ Materials Today: Proceedings 4 (2017) 10927–10934
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Abrasive wear is a severe wear therefore 1% Mn samples has shown higher wear rate when compared with the other samples. Three body abrasive wear is not a severe wear. Because free abrasive debris rolls between the rubbing surfaces but not remove the material considerable. Therefore it has shown minimum wear among the samples. This is observed in 0.5% Mn specimen. (a)
(b)
Laminated wear debris
Loose asperity particles
(c)
Abrasive wear debris
Fig. 4. SEM micro graph of wear debris at sliding speed of 2.5 m/s and at Nr. Pressure of 0.4996 MPa. (a) 0.2% Mn, (b) 0.5% Mn and (c) 1% Mn samples
4. Conclusions The observations made in this study suggest that the wear response depends on factors like composition, Nr. pressures and sliding speeds. Moderate addition of Mn into ZA-27 could reduce vol. wear rate. The experimental alloy with Mn content of approximately 0.5% has the least vol. wear rate observed. For all the samples at all sliding speeds, vol. wear rate is increased with increase in the Nr. pressure, further it is decreased with increasing in sliding speed up to 1.5 m/s. Hence, 1.5 m/s Sliding speed can be considered as critical sliding speed for ZA-27 alloy. At this sliding speed variation in vol. wear rate is minimum under different Nr. pressures for all samples. Nr. pressure of 0.2498 MPa is considered as a critical Nr. pressure. Frictional force is increased with increase in the Nr. pressure and sliding speed for all the samples. Reference [1] V Algur, V R Kabadi, Genechari S M and Sharanabasappa ‘Experimental Investigation on Friction Characteristics of Modified ZA-27 Alloy Using Taguchi Technique’. Int. J. Mech. Eng. & Rob. Res. 3 ( 2014) 24-32. [2] Geng Hao-ran, CUI Feng, Tian Xian-fa, Qian Bao-guang, “Processing technique and sliding friction and wear behaviour of TiB2/ZA-27 compostie”, J.Cent. South Univ. Technology, 12( 2005). [3] Zulkuf Balalan, Mehmet Kaplan, “Investigation of the Microstructure and Wear properties of a Cast ZA Alloy”, Int Jour of Sci & Tech., 2 (2007) 75-81.
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Veerabhadrappa Algur/ Materials Today: Proceedings 4 (2017) 10927–10934
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