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20120130406023
20120130406023
20120130406023
20120130406023
20120130406023
20120130406023
20120130406023
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20120130406023

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  • 1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 6, September – October (2013), © IAEME ENGINEERING AND TECHNOLOGY (IJARET) ISSN 0976 - 6480 (Print) ISSN 0976 - 6499 (Online) Volume 4, Issue 6, September – October 2013, pp. 222-228 © IAEME: www.iaeme.com/ijaret.asp Journal Impact Factor (2013): 5.8376 (Calculated by GISI) www.jifactor.com IJARET ©IAEME AN EXPERIMENTAL STUDY OF WEAR RESISTANCE OF AL – SIC COATINGS ON STEEL SUBSTRATE Dalip Kumar1, Antariksha Verma2, Sankalp Kulshrestha3 1 (Department of Mechanical Engineering, Delhi College of Engineering / Delhi Technological University, Main Bawana Road -Delhi India) 2, 3 (Department of Mechanical Engineering, Jodhpur Engineering College & Research Centre / Jodhpur National University Jodhpur – Rajasthan, India) ABSTRACT Al and Al–SiC composites coatings were prepared by oxyacetylene flame spraying process on steel substrate. Coatings with controlled reinforcement rate were obtained by spraying mixtures containing aluminum powder with 20 vol. %, 30 vol.%, and 50 vol.% SiC particles. The wear behavior of these coatings has been tested using the Pin-on-Disc technique under dry sliding conditions. The wear resistance of the aluminum coatings was greatly enhanced by the incorporation of the SiC reinforcement. The wear rate of the coating was found increased with increase in load. The co-efficient of coating was found decreased with increased SiC particle. The worn surfaces were examined using SEM (Scanning Electron Microscope), and it was found that the main wear mechanism was due to adhesion, abrasion and deformation. KEYWORDS: Al-SiC, Thermal Spray Coating, Wear Rate, Wear Mechanism. 1. INTRODUCTION Many kinds of surface modification processes are applied to improve the wear resistance of Al alloy [1]. Among coating processes, thermal spraying is superior one, capable of coating a thick layer in short operating time. Taking the weight saving effect into consideration, Al-base material is beneficial as a coating material. However, there is little research on the combination of the Al alloy substrate and the coating materials of Al alloy [2–4], including Al-base metal matrix composite with SiC, TiC, Al2O3 or FeO+TiO2 as reinforcement as the coating material [2–3]. B. Torres et. al [5] investigated that Aluminum matrix composite coatings reinforced with more than 20vol.% of SiC particles, wear resistance of the aluminum coatings was greatly enhanced by the incorporation of the SiC reinforcement which delayed the transition from mild to severe wear.Due to the refined silicon particle size and high volume fraction of silicon, thewear resistance is improved by this type of 222
  • 2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 6, September – October (2013), © IAEME surface treatment. Precipitation of iron aluminides with high volume fraction in aluminum matrix makes a composite surface layer to increase the hardness and wear resistance. High Si- and Febearing modified layers have low toughness so that cracking is easy to occur in operation. Anodizing, deposition and vacuum arc technologies [6]are also useful to yield thick aluminumoxide protective layer.Al and Al–SiC composites coatings were prepared by oxyacetylene flame spraying on ZE41 magnesiumalloy substrates. Coatings with controlled reinforcement rate of up to 23 vol. % were obtained by sprayingmixtures containing aluminum powder with up to 50 vol.% SiC particles. The coatings were sprayed onthe magnesium alloy with minor degradation of its microstructure or mechanical properties. Thecoatings were compacted to improve their microstructure and protective behavior. The wear behavior of these coatings has been tested using the pin-on-disk technique and the reinforced coatings provided85% more wear resistance than uncoated ZE41 and 400% more than pure Al coatings [7]. In this work, aluminum matrix composite coatings reinforced with 20 vol. %, 30 vol. % & 50 vol. % of SiC particles have been deposited using oxyacetylene flame spraying on steel substrates. The wear behaviourof these coatings has been tested using the pin-on-disk technique under dry sliding conditions. 2. EXPERIMENTAL PROCEDURE 2.1 Materials Aluminum matrix composite coatings reinforced with 20 vol. %, 30 vol. % & 50 vol. % of SiC particles have been deposited using oxyacetylene flame spraying on steel substrates. To improve the adhesion of the sprayed coatings, the substrates were sand blasted by abrasives of about 1 mm diameter to obtain surface with an average roughness of 10.5±0.7 mm. The samples were cleaned in ultrasonic wave in acetone and dried with air to avoid that any grease from the grinding system would reduce the adhesion of the coatings.The aluminum powder was mixed with SiC particles with an average size of 50 mmusing a conventional rotating ball milling machine with alumina balls for 40 min in dry conditions. Mixtures containing 20 vol. %, 30 vol. % and 50 vol. % of SiC particles were directly fed into the thermal spray gun for their simultaneous spraying. The spraying was carried out with an oxyacetylene thermal spray.The material feeding rate was 2.0 g/s, approximately, and the spray gun was passed twice over each sample to obtain coatings with thicknesses in the 400– 450 mm range. 2.2 Wear test Wear tests were carried out under dry sliding condition using a Pin-on-Disc (Wear and friction monitor, DTU, Delhi) set up. The counter body was a 6 mm diameter alumina pin.Specimen andcounter body surfaces were cleaned with acetone to avoid the presence of humidity and nondesirable deposits. The tests were performed in ordinary laboratory environment at RH30% and20°C. The wear test was carried out with 10N, 20N and 30 N load and 200 rpm sliding speed. Specimens were also weighted before and after the tests with a 0.00001 g balance to measure the mass loss. The coefficient of friction was obtained by means of a torquetransducer. The wear rate is determined in terms of mass loss in g per 70 meter of sliding distance. 3. RESULTS & DISCUSSION 3.1 Micro structural characterization of sprayed coatings The porosity of the coating was very low (Fig. 1a). As a result of morphology, the actual porosity measured on the transversal section of the coatings was 2.9%.The morphology of the coatings was the usual one of thermally sprayed ones; the coating was formed by the accumulation of 223
  • 3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 6, September – October (2013), © IAEME splats and the presence of localized defects between them was the main cause for the apparition of porosity (Fig. 1 b). The splats at the substrate-coating interface deformed and followed the substrate topography without leaving voids (Fig. 2a). The substrate microstructure did not seem to be modified by thespraying procedure (Fig. 2b).The mean porosity of the coatingwas 4.1% throughout the spraying procedure. Fig. 1 (a) Microstructure of sprayed aluminum alloy coating at 100X (b) Microstructure of Al-20% SiC particles composite coating at 100X Fig. 2 (a) Microstructure of Al-30% SiC particles composite coating at 100X (b)Microstructure of Al-50% SiC particles composite coating at 100X 3.2 Wear rate The wear rate versus normal load, for the different coatings analyzed are shown in Fig. 3 As it can be observed in the figure, the wear rate of Al/SiCp composites increased with normal load. In addition, the wear resistance of thealuminumcoatingswasgreatly reduces by the use of SiCp. 224
  • 4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 6, September – October (2013), © IAEME Load (N) 10 20 30 Weight Loss Material Weight Loss (g) 0.017 0.025 0.032 Al (Pure) 0.012 0.018 0.023 Al+20%SiC 0.009 0.013 0.015 Al+30%SiC 0.005 0.009 0.011 Al+50%SiC Table 1 Weight Loss in g at constant speed of 200rpm and weight of 10, 20 & 30 N at70 Meter Sliding Distance 0.035 Wear Rate (g) 0.03 0.025 Al 0.02 Al+20%SiC 0.015 Al+30%SiC 0.01 Al+50%SiC 0.005 0 0 10 20 30 40 Load (N) Fig. 3 Variation of Wear Rate with Load The addition of SiC particle to thecoating reduced the wear rates by a strong amount. With the addition of load there is increase in wear rate. The wear rate was high in case of pure aluminum, but with the addition of SiC particle the wear rate was found decreased [8]. 3.3 Co- efficient of Friction Friction coefficients were similarin all the tests; they increased slightly with the incorporation of the pure aluminum coating and reduced with the incorporation ofSiC particles into the coatings. The coefficient of friction is high for pure aluminum because of adhesion between aluminum coating and counter body. This was also favoured by the higher plastic deformation of the aluminum coating as a result of its lower hardness.The presence of SiC particles reduced the adhesion between the ball and the coatings and also reduced the deformation of thecoatings. There is negligible effect of load on the co-efficient of friction. Load (N) 10 20 30 Co-efficient of Friction (µ) Material Co-efficient of Friction (µ) 0.46 0.45 0.47 Al (Pure) 0.54 0.53 0.54 Al+20%SiC 0.71 0.72 0.73 Al+30%SiC 0.88 0.87 0.89 Al+50%SiC Table 2 Co-efficient of Friction at constant speed of 200rpm and weight of 10, 20 & 30 N at70 Meter Sliding Distance 225
  • 5. Co-efficient of Friction International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 6, September – October (2013), © IAEME 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 Al Al+20%SiC Al+30%SiC Al+50%SiC 0 10 20 30 40 Load (N) Fig. 4 Variation of Co-efficient of friction with Load 3.4 Wear Mechanism In order to determine the main wear mechanism, the worn surfaces of Al and SiC particles composites were observed by SEM.The presence of voids and cracks along the wear path in the surface of the worn as-sprayed aluminum coating, apart from thedrag lines, evidenced the simultaneous action of abrasive, adhesive and delaminating wear mechanisms. However, the contribution of delaminating and adhesive wear to the total degradation of the samples seemed to be higher than the effect of abrasion. The roleplayed by adhesion was also confirmed by the irregular shape ofthe sides of the wear path (Fig. 5a).Big substrate cracks appear indicating that delamination wear took place. Fig. 5 (a) Microstructure of worn surface of sprayed pure aluminum coating at 100X (b) Microstructure of worn surfaces of Al-20% SiC particles composite coating at 100X The worn coatings reinforced with the low SiC particle content,observed at higher magnificationsshowed evidence ofabrasion and adhesion. The cracks does not propagate into surface, it shows that delamination wear did not take place (Fig. 5b).The adhesion mechanisms were less important than in the pure aluminum coating becausefewer voidswere observed. 226
  • 6. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 6, September – October (2013), © IAEME Fig. 6(a) Microstructure of worn surfaces of Al-30% SiC particles composite coating at 100X (b) Microstructure of worn surfaces of Al-50% SiC particles composite coating at 100X As SiC particles increased to 30 vol. % as shown in Fig. 6a, the adhesion was observed very less after the wear test. The sprayed coating with highest reinforcement 50% SiC, was less affected by adhesive failure (Fig. 6b). The high density of SiC particles seems to control the propagation of crack growth. Finally, the presence of SiC particles reduced the mechanical deformation of the coating, limiting the integration of the different splats, but transferring the loads to the substrate coating interface, favouring the delamination of the coating. 4. CONCLUSIONS 1. Aluminum and aluminum matrix composite coatings reinforced with 20 vol.% SiCp, 30 vol. % SiCp and 50 vol. % SiCp have been successfully prepared oxy-acetylene thermal spraying process on steel substrates. 2. The wear rate was found increased with increase in load. 3. The wear rate was greatly reduced with the addition of SiC particles reinforcement. 4. The Co-efficient of friction of the coating was found decreased with increase in SiC particles reinforcement. 5. There was no effect of increase of load on co-efficient of friction. 6. The addition of SiCparticles reduced plastic deformation and increased the wear resistance of the coating. 7. The wear mechanism with pure aluminum coating was due to adhesion, Abrasion and deformation. With high SiC particle reinforcement the wear mechanism was due to abrasion and deformation. REFERENCES 1. K. Nakata, T. Hashimoto, Proceedings of the Seventh International Seminar of IFHT on Heat Treatment and Surface Engineering of Light Alloys, September 1999, Budapest, Hungary, 85–94. 2. Z. Mutasim, L. Hsu, Proceedings of the Seventh NTSC, June1994, Boston, MA, 85–91. 3. G. Barbezat, S. Keller, K.H. Wegner, Proceedings ITST’95, May 1995, Kobe, Japan, 9 13. 4. K. Nakata, M. Ushio, Surf. Coat. Technol. 142–144(2001)277–282. 227
  • 7. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 6, September – October (2013), © IAEME 5. B. Torres, M.A. Garrido, A. Rico, P. Rodrigo, M. Campo, J. Rams, Wear behaviour of thermal spray Al/SiCp coatings, Wear268 (2010) 828–836. 6. Z.W. Zhao, B.K. Tay, D. Sheeja, Structural characteristics and mechanical properties of aluminum oxide thin films prepared by off-plane filtered cathodic vacuum arc system, Surf. Coat. Technol. 167(2003) 234–239. 7. P. Rodrigo, M. Campo, B. Torres, M.D. Escalera, E. Otero, J. Rams, Microstructure and wear resistance of Al–SiC composites coatings on ZE41magnesium alloy, Applied Surface Science 255 (2009) 9174–9181. 8. B. Torres, M.A. Garrido, A. Rico, P. Rodrigo, M. Campo, J. Rams, Wear behaviour of thermal spray Al/SiCp coatings, Wear 268 (2010) 828–836. 9. Amol D. Sable and Dr. S. D. Deshmukh, “Characterization of AlSic Metal-Matrix by Stircasting”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 3, Issue 2, 2012, pp. 226 - 234, ISSN Print: 0976-6480, ISSN Online: 0976-6499. 10. P. Kurmi, S. Rathod and P. Jain, “Abrasive Wear Behavior of 2014al-Tic in Situ Composite”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 3, 2012, pp. 229 - 240, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. 11. P. Kurmi, S. Rathod and P. Jain, “Abrasive Wear Behavior of 2014al-Tic in Situ Composite”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 3, 2012, pp. 229 - 240, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. 12. Vandana Gupta and S.B. Singh, “Mathematical Model of Creep Behavior in an Anisotropic Rotating Disc of Al-Sicp with Thickness Variation in Presence of Thermal Residual Stress”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 2, 2012, pp. 274 - 283, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. 13. Jeevan.V, C.S.P Rao and N.Selvaraj, “Compaction, Sintering and Mechanical Properties of AlSicp Composites”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 3, Issue 3, 2012, pp. 565 - 573, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359. 228

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