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Wear behaviour of Electron beam surface melted Inconel 718
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Procedia Manufacturing 00 (2019) 000–000
Procedia Manufacturing 35 (2019) 866–873
2nd International Conference on Sustainable Materials Processing and Manufacturing 2nd International Conference on Sustainable Materials Processing and Manufacturing (SMPM 2019) (SMPM 2019)
Wear behaviour of Electron beam surface melted Inconel 718 Wear behaviour of Electron beam surface melted Inconel 718 Sumit K. Sharma, K. Biswas, J. Dutta Majumdar * SumitofK. Sharma, K. Biswas, J. Dutta Majumdar Department Metallurgical & Materials Engineering, I. I. T. Kharagpur721302,* India Department of Metallurgical & Materials Engineering, I. I. T. Kharagpur- 721302, India
Abstract Abstract This study concerns understanding the wear behavior of electron beam surface melted Inconel 718. Electron beam surface melting has been carried out using an indigenously developed electron beam welding machine with a capacity of 80kV, 12 kW. This study concerns understanding the awear behavior of electron beam surface melted Inconel 718. Electron beam surface Surface melting has been carried under varied combination of beam current and scan speed to optimize the process parameter melting has been out using an indigenously electron beam welding machine with 80kV, 12 kW. of electron beamcarried melting corresponding to the developed development of defect free processed zone.a capacity Detailed ofinvestigation of Surface melting phase, has been carried under a varied combination of beam and scan speed to optimize the process parameter microstructure, hardness, and reciprocating friction wear havecurrent been carried out. Finally, the fretting wear behavior of of electron beam melting to the development of defect zone. Detailed investigation of electron beam melted Inconelcorresponding 718 has been evaluated against tungsten carbidefree ball processed under fretting wear mode and compare with microstructure, phase, hardness, and reciprocating friction wear have been carried out. Finally, the fretting wear behavior of the fretting wear behavior of as received Inconel 718. Finally, the mechanism and kinetics of wear have been investigated threw a electron beam meltedanalysis Inconel of 718 been evaluated against tungsten carbide ball under fretting wear mode and compare with detail microstructure thehas worn surface. the fretting wear behavior of as received Inconel 718. Finally, the mechanism and kinetics of wear have been investigated threw a detail microstructure analysis of the worn surface. © 2019 The Authors. Published by Elsevier B.V. © 2019 The Authors. Published by B.V. committee of SMPM 2019. Peer-review under responsibility ofElsevier the organizing Peer-review under responsibility ofElsevier the organizing © 2019 The Authors. Published by B.V. committee of SMPM 2019. Peer-review under beam responsibility of theInconel organizing Keywords: Electron melting; Wear; 718 committee of SMPM 2019. Keywords: Electron beam melting; Wear; Inconel 718
1. Introduction 1. Introduction Inconel 718 is a Ni based superalloy having Cr, Nb, Mo, are key elements (17-21 wt % Cr, 5-6 wt% Nb, 3-3.5 wt. %, 0.6-1.2 wt.% Ti, and 0.2-0.8 wt.% Al). It is widely used in aerospace application, structure materials and Inconel 718 as is ahigh Ni based superalloy having Cr, Nb, Mo, are key elementschemical (17-21 wtvapour % Cr, deposition, 5-6 wt% Nb,Electro 3-3.5 marine sectors temperature alloy. [1] Physical vapour deposition, wt. %, 0.6-1.2 wt.% Ti, and 0.2-0.8 wt.% Al). It is widely used in aerospace application, structure materials and marine sectors as high temperature alloy. [1] Physical vapour deposition, chemical vapour deposition, Electro * Corresponding author E-mail address: [email protected] * Corresponding author E-mail address: [email protected] 2351-9789 © 2019 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the organizing committee of SMPM 2019. 2351-9789 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the organizing committee of SMPM 2019.
2351-9789 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the organizing committee of SMPM 2019. 10.1016/j.promfg.2019.06.033
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Sumit K. Sharma et al. / Procedia Manufacturing 35 (2019) 866–873 Author name / Procedia Manufacturing 00 (2019) 000–000
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deposition and Thermal spray deposition are the main surface treatment techniques, which minimizes wear and erosion characteristics of the material. [2] Electron beam as a source of hear has potential scope of application for materials processing [3]. However, most of the research effort in this regard is in the field of welding [4]. However, as a tool of heat it’s having the possibility of developing melt surface with a thick contaminant free melt zone, narrow heat affected zone and minimum defect density. However, limited effort has been made to understand the effect of electron beam melting on microstructures, phases, surface properties and hence, a detailed understanding of structure-property correlation. In electron beam melting, the energy deposition to the surface by electron beam produces transient heating, melting and rapid cooling, resulting in improvement of surface properties, in terms of hardening, fatigue resistance, corrosion resistance and surface roughness. Rapid cooling introduced by surface melting produces a sufficient hardening effect, which was evolved by both microstructure refinement and solid solution strengthening. In the past, though Laser beam has reportedly been used for surface melting of metals and alloys to improve surface dependent engineering properties, especially corrosion resistance. However, a limited literature is available on electron beam assisted surface melting of metals and alloys. In the present investigation, the effect of the microstructure and mechanical properties have been studied in details. 2. Experimental The Inconel 718 aged condition was used as substrate in the present study. The composition of which is summarized in table: 1 Table 1: Summary of the Composition of INCONEL 718 determined by XRF Analysis Elements Percentage (Wt%)
Ni 51.42
Cr 17.30
Fe 20.67
Mo 3.04
Nb 5.01
Mn 0.02
Cu 0.02
Al 1.66
Ti 0.83
C,S,P,B 0.04
The Inconel 718 substrate was cut to a dimension of 25*25*3 mm and mechanically polished to a roughness of 25µm. prior to surface Processing. Electron beam surface processing was conducted using an 80 kV, 12 kW conventional electron beam welding unit (made by Bhabha Atomic Research Centre India) with the process parameter as summarized parameters in table-2 Table 2: Electron beam Surface melting parameters for Inconel 718 alloy Sample ID
Scan Speed (mm/min)
A B C D
Voltage (kV)
Beam Current (mA)
Heat input (J/mm)
As-received Inconel base metal 500 750 1000
40 40 40
10 10 10
48 32 24
The microstructures of melt zone were observed by optical and scanning electron microscopy (SUPRA 40, Zeiss SMT AG, and Germany). The phases present in the melt zone were analyzed by X-ray diffraction (D8 Advances, Bruker AXS, Germany) study. Similarly, the mechanical properties hardness was also evaluated. Finally, Fretting Wear resistance properties was evaluated against tungsten carbide ball was evaluated by using a ball on disc wear testing unit against tungsten carbide as mating surface in the form of ball at an oscillating frequency of 10 Hz and a load of 10N. Finally, a detailed study of post wear microstructural damaged surface was observed using was carried out by scanning electron microscopy and correlated with kinetics of wear and coefficient of friction to understand the mode of wear.
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3. Result and discussion 3.1 Microstructure Analysis The scanning electron micrograph of the cross section of electron beam surface melted Inconel 718 using a voltage of 40 kV, current of 15 mA and scan speed of 500 mm/min is shown in Fig. 1(a). The detailed microstructure feature of Fig. 1(a) at high magnification is displayed in Fig. 1(b). Fig. 1(a) confirms that the depth of the melt zone varies from 300 microns to 400 microns, is semielliptical and maximum in the middle with substantiates that heat transfer is predominantly conduction dominated mode. The microstructure of the melt zone at high magnification shows the presence of refined microstructure with dendritic in morphology. In addition, average secondary interdendritic arm spacing is 1.5 micron. The depth of the melt zone and secondary interdendritic spacing of the melt zone were found to vary with process parameters of melting (beam current and scan speed) [5-7].
Figure 1. SEM images at the cross-section of Electron beam melted Inconel 718 using a voltage of 40 kV, current of 15 mA and a scan speed of 500 mm/min. (a) Interfacial zone, (b) interfacial region and (c) melted region.
3.2 Surface Roughness Study
Figure 2. Surface roughness of as received and electron beam melted Inconel 718 at different parameters as samples A, B, C and D respectively.
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A detailed study of the average surface roughness of the melted zone was undertaken using optical profilometer (Icon Analytical Equipment Pvt. Ltd.) and is summarized in Fig. 2 IT is evident that there is increase in average surface roughness at different parameters. A systematic study shows that due to electron beam surface melting there is increase in surface roughness as compared to as received samples. Increase in scan speed was found to increase in surface roughness of the electron beam melted surface from 500 to 750 mm/min. However, at a very high scan speed (1000 mm/min) there is decrease in surface roughness. Increase in surface roughness with increase in scan speed is attributed to surface ripples induced by Marangoni dominated heat flow and crater formation on the surface due to localized evaporation of materials from the surface. At a very high velocity, there is decrease in surface roughness because of a reduced evaporation rate from surface because of application of low energy density. 3.3 X-Ray Diffraction Study Fig. 3 Shows the X-ray diffraction profile of as received Inconel 718 (Plot A) and electron beam surface melted Inconel 718 using an acceleration voltage 40 kV, current of 10 mA, and scan speed of 500 mm/min (plot B), 750 mm/min (plot C) and 100 mm/min (plot D). From Fig. 2 it may be noted that due to electron beam surface melting there is no significant change in phases and no signature of contamination as compared to as received Inconel 718. [8] However, variation of crystalline size, lattice strain and texture with process parameters has been shown in table 3.
Figure 3. XRD pattern of as received and Electron beam melted Inconel 718 at different parameters as A, B, C and D respectively. Table 3: Crystalline size, Lattice strain and texture coefficient measured threw X-ray diffraction analysis. Sample ID
Average Crystalline Size [A0]
A B C D
131.5 379.7 360.7 458.5
Lattice Strain [%] 0.838 0.270 0.284 0.325
Texture Coefficient
0.717 For (111) plane 0.319 For (111) plane 0.039 For plane (022) 0.234 For plane (022)
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3.4 Micro Hardness Profile
Figure 4. average microhardness distribution of as received and EB melted Inconel 718 at different parameters as samples A, B, C and D respectively.
Fig. 4 shows the variation of average surface microhardness with depth from the surface of Inconel 718 melted with Speed (at 500 mm/min, 750 mm/min, and 1000 mm/min). From Fig. 4. It may be noted that the average surface hardness increases with depth up to a certain depth (200 to 300 micron) and then decreases to substrate microhardness. Attainment of maximum surface hardness in region below the surface is attributed to coarsening of microstructure at near the surface region as compared to below surface region. Both the microhardness of the surface and subsurface zone were found to vary with process parameters. In this regard it may be noted that a maximum microhardness at the surface and subsurface region is achieved when melting was conducted at an applied scan speed of 500 mm/min. and minimum hardness were observed for the samples processed with scan speed of 750 mm/min. Than improved microhardness in melted zone as compared to as received substrate is attributed to possibly grain refinement due to surface melting [9-11]. 3.5 Fretting Wear Study Fig. 5(a-c) show the variation of (a) wear depth as a function of interaction time (b) coefficient of friction as function of interaction time (c) summary of wear rate for all the samples. From fig. 5 (a), it may be noted that there is reduction in the wear rate follows two different kinetics. The initial faster kinetics followed by slower kinetics a later stage.it may further be noted that the kinetics of initial stage of wear (which is evident from the slope of wear depth vs time graph) the same for both as received and electron beam melted Inconel 718. However, the duration of initial faster kinetics varied with the processing condition of sample. For as received Inconel 718 the second stage of wear also follows linear kinetics. However, the kinetics of wear (rate of change of wear depth with time) is slower in the second stage as compared with first stage in Inconel 718. Followed by second stage of wear, the wear rate is almost remains negligible (there is no change in wear depth with time). For electron beam melted samples processed with 500 mm/min and 1000 mm/min, scan speed shows the initial faster kinetics for a little longer duration than as received Inconel 718 and thereafter the wear rate remains negligible. On the other hand, electron beam melted surface processed with 750 mm/min shows faster kinetics at the initial stage for shorter duration as compared to that of unmelted Inconel 718. For a shorter duration and then it decreases but followed linear kinetics up to 600 second of interaction time and become negligible thereafter. From Fig. 5(a) it may further be noted that due to electron beam surface melting there is improvement in wear resistance in terms of maximum depth of wear under steady state as compared to as received Inconel 718. A detailed study of variation of coefficient of friction with time shows that there is sharp rise in coefficient of friction at the initial stage followed by with it remains same in as received Inconel 718 for a certain period of time followed with it
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reduce to a very low value. Initial rise in coefficient of friction is as received Inconel 718 is attributed to mechanical interlocking between the mating surfaces following with there is damage of interlock coins because sliding motion and its subsequent damage causing the worn out debris occupying the space between the mating surfaces and changing the mode wear from two body wear to three body wear. For other electron beam melted samples Inconel 718 to the coefficient of friction increases to a very high value at the initial stage. However, the intermediate constant coefficient of friction value is missing. At a later stage there is drop in coefficient of friction and remains constant thereafter. A detailed study of average wear rate of all samples show that a minimum wear rate is observed samples electron beam melted with 500 mm/min [12].
Figure 5 (a) Kinetics of wear in terms of cumulative depth of wear as a function of time (b) coefficient of friction as function of time and (c) Wear rate for as received and Electron beam melted Inconel 718 at different parameters as A, B, C and D respectively.
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Figure 6 (a-d) shows the Scanning electron micrograph of worned scar of (a) as received Inconel 718 (b) electron beam melted Inconel 718 and the same at high magnification, (c) As received Inconel 718 and (d) electron beam melted Inconel. .
To understand the mechanism of wear a detailed study on microstructures of the worn-out debris were performed. The scanning electron micrographs of the worn out surface of as received and melted Inconel 718 have been presented in Figs. 6(a) - (d). The figures clearly depict the presence of micro cracks with fine scratches along with presence of micro-deformation band. Presence of micro cracks and fine scratches are due to high stress fretting wear in addition to abrasive wear acting on the surface. A closed comparison of the worned out surfaces of as received Inconel 718 with the melted surface shows that. Fig. 6(a-d) show the scanning electron micrograph of worned scar of as received Inconel 718 (b) electron beam melted Inconel 718 and the same at high magnification, (c) As received Inconel 718 and (d) electron beam melted Inconel. A comparison between Figures 4(a) and 4(b) Shows that there is no significant change in the dimension of worn scar in EB melted Inconel 718 as compared to as received Inconel 718. The high magnification view of the same shows that there is presence of microgrooves, micro cracks, and micro deformation from the surface. The groove formation is the signature of adhesive wear micro cracks are visible because of application of high stress during wear and micro deformation region are due to fretting motion. On the other hand, electron beam melted Inconel 718 shows worned surface of electron beam melted Inconel 718 shows discontinuous nature of worned region micro roughening of the surface because accumulation of worned debris and its adhesion of the surface. 4. Conclusions In this study the electron beam surface melting of Inconel 718 has been successfully performed and its effects on microstructure and wear behavior has been analyzed and following conclusion can be made: • Electron beam melting is basically used to refine the microstructures and also eliminate the precipitates by its dissolution in the matrix. Dendritic grain structures and was reported in which heterogeneous grain nucleation at the substrate melt interface is dominant. • Electron beam melting of Inconel 718 at varying parameters like scan speed showed improved surface roughness. After melting surface rippling takes place on surface and surface tension increases. The average microhardness of Electron beam melted alloy increases for every enhanced scan speed. • XRD Analysis of the electron beam surface melted seam broadly marked the presence of austenitic γ – Ni, precipitated and γ’ Ni3(Al,Ti). • Electron beam melted samples processed with 500 mm/min and 1000 mm/min, scan speed shows the initial faster kinetics for a little longer duration than as received Inconel 718 and thereafter the wear rate remains negligible
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Sumit K. Sharma et al. / Procedia Manufacturing 35 (2019) 866–873 Author name / Procedia Manufacturing 00 (2019) 000–000
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•
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Electron beam melted samples Inconel 718 to the coefficient of friction increases to a very high value at the initial stage. However, the intermediate constant coefficient of friction value is missing. At a later stage there is drop in coefficient of friction and remains constant thereafter. Worn surface of electron beam melted Inconel 718 shows discontinuous nature of worn region micro roughening of the surface because accumulation of worn debris and its adhesion of the surface.
Acknowledgement Author is highly grateful for the partial financial support from the Board of Nuclear Science (BRNS). References [1]
K. Zhao, Y. H. Ma, L. H. Lou, and Z. Q. Hu, “Abnormal precipitation behavior of Ni3Al phase,” Mater. Sci. Eng. A, vol. 480, no. 1–2, pp. 205–208, 2008.
[2]
G. Di Girolamo, M. Alfano, L. Pagnotta, a. Taurino, J. Zekonyte, and R. J. K. Wood, “On the early stage isothermal oxidation of APS CoNiCrAlY coatings,” J. Mater. Eng. Perform., vol. 21, no. 9, pp. 1989–1997, 2012.
[3]
Soumyabrata Basak, Sumit K. Sharma, and J. Dutta Majumdar, “Studies on electron beam surface melting of AISI 316 stainless steel and AISI 347 stainless steel, procedia manufacturing 7 (2016) 647-653.
[4]
Soumitra Kumar Dinda, Md. Basiruddin Sk, Gour Gopal Roy, and Prakash Srirangam “Microstructure and mechanical properties of electron beam welded dissimilar steel to Fe-Al alloy joints,” Materials Science & Engineering A, Vol. 677, pp 182-192, 2016
[5]
J. D. Majumdar and I. Manna, “Laser surface alloying of copper with chromium II . Improvement in mechanical properties,” vol. 268, pp. 227–235, 1999.
[6]
J. D. Majumdar and I. Manna, “Laser surface alloying of AISI 304-stainless steel with molybdenum for improvement in pitting and erosion – corrosion resistance,” vol. 267, pp. 50–59, 1999.
[7]
A. D. Patel and Y. V Murty, “Effect of Cooling Rate on Microstructural Development in Alloy 71 8,” Superalloys 718, 625 Var. Deriv., pp. 123–132, 2001.
[8]
C. Zonglin, W. Shaogang, and L. I. Weihong, “! 850 8,” vol. 6, pp. 769–771, 1997.
[9]
J. Kim, J. Kim, E. Kang, and H. Wook, “Applied Surface Science Surface modification of the metal plates using continuous electron beam process ( CEBP ),” Appl. Surf. Sci., vol. 311, pp. 201–207, 2014.
[10]
K. Mumtaz and N. Hopkinson, “Top surface and side roughness of Inconel 625 parts processed using selective laser melting,” Rapid Prototyp. J., vol. 15, no. 2, pp. 96–103, 2009.
[11]
Y. Tian, D. Tomus, P. Rometsch, and X. Wu, “Influences of processing parameters on surface roughness of Hastelloy X produced by selective laser melting,” Addit. Manuf., vol. 13, pp. 103–112, 2017.
[12]
Subhasisa Nath, Sisa Pityana, Jyotsna Dutta Majumdar, “Laser surface alloying of aluminium with WC+Co+NiCr for improved wear resistance,” Surface & Coatings Technology 206 (2012) 3333–3341
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Procedia Manufacturing 35 (2019) 866–873
2nd International Conference on Sustainable Materials Processing and Manufacturing 2nd International Conference on Sustainable Materials Processing and Manufacturing (SMPM 2019) (SMPM 2019)
Wear behaviour of Electron beam surface melted Inconel 718 Wear behaviour of Electron beam surface melted Inconel 718 Sumit K. Sharma, K. Biswas, J. Dutta Majumdar * SumitofK. Sharma, K. Biswas, J. Dutta Majumdar Department Metallurgical & Materials Engineering, I. I. T. Kharagpur721302,* India Department of Metallurgical & Materials Engineering, I. I. T. Kharagpur- 721302, India
Abstract Abstract This study concerns understanding the wear behavior of electron beam surface melted Inconel 718. Electron beam surface melting has been carried out using an indigenously developed electron beam welding machine with a capacity of 80kV, 12 kW. This study concerns understanding the awear behavior of electron beam surface melted Inconel 718. Electron beam surface Surface melting has been carried under varied combination of beam current and scan speed to optimize the process parameter melting has been out using an indigenously electron beam welding machine with 80kV, 12 kW. of electron beamcarried melting corresponding to the developed development of defect free processed zone.a capacity Detailed ofinvestigation of Surface melting phase, has been carried under a varied combination of beam and scan speed to optimize the process parameter microstructure, hardness, and reciprocating friction wear havecurrent been carried out. Finally, the fretting wear behavior of of electron beam melting to the development of defect zone. Detailed investigation of electron beam melted Inconelcorresponding 718 has been evaluated against tungsten carbidefree ball processed under fretting wear mode and compare with microstructure, phase, hardness, and reciprocating friction wear have been carried out. Finally, the fretting wear behavior of the fretting wear behavior of as received Inconel 718. Finally, the mechanism and kinetics of wear have been investigated threw a electron beam meltedanalysis Inconel of 718 been evaluated against tungsten carbide ball under fretting wear mode and compare with detail microstructure thehas worn surface. the fretting wear behavior of as received Inconel 718. Finally, the mechanism and kinetics of wear have been investigated threw a detail microstructure analysis of the worn surface. © 2019 The Authors. Published by Elsevier B.V. © 2019 The Authors. Published by B.V. committee of SMPM 2019. Peer-review under responsibility ofElsevier the organizing Peer-review under responsibility ofElsevier the organizing © 2019 The Authors. Published by B.V. committee of SMPM 2019. Peer-review under beam responsibility of theInconel organizing Keywords: Electron melting; Wear; 718 committee of SMPM 2019. Keywords: Electron beam melting; Wear; Inconel 718
1. Introduction 1. Introduction Inconel 718 is a Ni based superalloy having Cr, Nb, Mo, are key elements (17-21 wt % Cr, 5-6 wt% Nb, 3-3.5 wt. %, 0.6-1.2 wt.% Ti, and 0.2-0.8 wt.% Al). It is widely used in aerospace application, structure materials and Inconel 718 as is ahigh Ni based superalloy having Cr, Nb, Mo, are key elementschemical (17-21 wtvapour % Cr, deposition, 5-6 wt% Nb,Electro 3-3.5 marine sectors temperature alloy. [1] Physical vapour deposition, wt. %, 0.6-1.2 wt.% Ti, and 0.2-0.8 wt.% Al). It is widely used in aerospace application, structure materials and marine sectors as high temperature alloy. [1] Physical vapour deposition, chemical vapour deposition, Electro * Corresponding author E-mail address: [email protected] * Corresponding author E-mail address: [email protected] 2351-9789 © 2019 The Authors. Published by Elsevier B.V.
Peer-review under responsibility of the organizing committee of SMPM 2019. 2351-9789 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the organizing committee of SMPM 2019.
2351-9789 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the organizing committee of SMPM 2019. 10.1016/j.promfg.2019.06.033
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deposition and Thermal spray deposition are the main surface treatment techniques, which minimizes wear and erosion characteristics of the material. [2] Electron beam as a source of hear has potential scope of application for materials processing [3]. However, most of the research effort in this regard is in the field of welding [4]. However, as a tool of heat it’s having the possibility of developing melt surface with a thick contaminant free melt zone, narrow heat affected zone and minimum defect density. However, limited effort has been made to understand the effect of electron beam melting on microstructures, phases, surface properties and hence, a detailed understanding of structure-property correlation. In electron beam melting, the energy deposition to the surface by electron beam produces transient heating, melting and rapid cooling, resulting in improvement of surface properties, in terms of hardening, fatigue resistance, corrosion resistance and surface roughness. Rapid cooling introduced by surface melting produces a sufficient hardening effect, which was evolved by both microstructure refinement and solid solution strengthening. In the past, though Laser beam has reportedly been used for surface melting of metals and alloys to improve surface dependent engineering properties, especially corrosion resistance. However, a limited literature is available on electron beam assisted surface melting of metals and alloys. In the present investigation, the effect of the microstructure and mechanical properties have been studied in details. 2. Experimental The Inconel 718 aged condition was used as substrate in the present study. The composition of which is summarized in table: 1 Table 1: Summary of the Composition of INCONEL 718 determined by XRF Analysis Elements Percentage (Wt%)
Ni 51.42
Cr 17.30
Fe 20.67
Mo 3.04
Nb 5.01
Mn 0.02
Cu 0.02
Al 1.66
Ti 0.83
C,S,P,B 0.04
The Inconel 718 substrate was cut to a dimension of 25*25*3 mm and mechanically polished to a roughness of 25µm. prior to surface Processing. Electron beam surface processing was conducted using an 80 kV, 12 kW conventional electron beam welding unit (made by Bhabha Atomic Research Centre India) with the process parameter as summarized parameters in table-2 Table 2: Electron beam Surface melting parameters for Inconel 718 alloy Sample ID
Scan Speed (mm/min)
A B C D
Voltage (kV)
Beam Current (mA)
Heat input (J/mm)
As-received Inconel base metal 500 750 1000
40 40 40
10 10 10
48 32 24
The microstructures of melt zone were observed by optical and scanning electron microscopy (SUPRA 40, Zeiss SMT AG, and Germany). The phases present in the melt zone were analyzed by X-ray diffraction (D8 Advances, Bruker AXS, Germany) study. Similarly, the mechanical properties hardness was also evaluated. Finally, Fretting Wear resistance properties was evaluated against tungsten carbide ball was evaluated by using a ball on disc wear testing unit against tungsten carbide as mating surface in the form of ball at an oscillating frequency of 10 Hz and a load of 10N. Finally, a detailed study of post wear microstructural damaged surface was observed using was carried out by scanning electron microscopy and correlated with kinetics of wear and coefficient of friction to understand the mode of wear.
Sumit K. Sharma et al. / Procedia Manufacturing 35 (2019) 866–873 Author name / Procedia Manufacturing 00 (2019) 000–000
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3. Result and discussion 3.1 Microstructure Analysis The scanning electron micrograph of the cross section of electron beam surface melted Inconel 718 using a voltage of 40 kV, current of 15 mA and scan speed of 500 mm/min is shown in Fig. 1(a). The detailed microstructure feature of Fig. 1(a) at high magnification is displayed in Fig. 1(b). Fig. 1(a) confirms that the depth of the melt zone varies from 300 microns to 400 microns, is semielliptical and maximum in the middle with substantiates that heat transfer is predominantly conduction dominated mode. The microstructure of the melt zone at high magnification shows the presence of refined microstructure with dendritic in morphology. In addition, average secondary interdendritic arm spacing is 1.5 micron. The depth of the melt zone and secondary interdendritic spacing of the melt zone were found to vary with process parameters of melting (beam current and scan speed) [5-7].
Figure 1. SEM images at the cross-section of Electron beam melted Inconel 718 using a voltage of 40 kV, current of 15 mA and a scan speed of 500 mm/min. (a) Interfacial zone, (b) interfacial region and (c) melted region.
3.2 Surface Roughness Study
Figure 2. Surface roughness of as received and electron beam melted Inconel 718 at different parameters as samples A, B, C and D respectively.
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A detailed study of the average surface roughness of the melted zone was undertaken using optical profilometer (Icon Analytical Equipment Pvt. Ltd.) and is summarized in Fig. 2 IT is evident that there is increase in average surface roughness at different parameters. A systematic study shows that due to electron beam surface melting there is increase in surface roughness as compared to as received samples. Increase in scan speed was found to increase in surface roughness of the electron beam melted surface from 500 to 750 mm/min. However, at a very high scan speed (1000 mm/min) there is decrease in surface roughness. Increase in surface roughness with increase in scan speed is attributed to surface ripples induced by Marangoni dominated heat flow and crater formation on the surface due to localized evaporation of materials from the surface. At a very high velocity, there is decrease in surface roughness because of a reduced evaporation rate from surface because of application of low energy density. 3.3 X-Ray Diffraction Study Fig. 3 Shows the X-ray diffraction profile of as received Inconel 718 (Plot A) and electron beam surface melted Inconel 718 using an acceleration voltage 40 kV, current of 10 mA, and scan speed of 500 mm/min (plot B), 750 mm/min (plot C) and 100 mm/min (plot D). From Fig. 2 it may be noted that due to electron beam surface melting there is no significant change in phases and no signature of contamination as compared to as received Inconel 718. [8] However, variation of crystalline size, lattice strain and texture with process parameters has been shown in table 3.
Figure 3. XRD pattern of as received and Electron beam melted Inconel 718 at different parameters as A, B, C and D respectively. Table 3: Crystalline size, Lattice strain and texture coefficient measured threw X-ray diffraction analysis. Sample ID
Average Crystalline Size [A0]
A B C D
131.5 379.7 360.7 458.5
Lattice Strain [%] 0.838 0.270 0.284 0.325
Texture Coefficient
0.717 For (111) plane 0.319 For (111) plane 0.039 For plane (022) 0.234 For plane (022)
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3.4 Micro Hardness Profile
Figure 4. average microhardness distribution of as received and EB melted Inconel 718 at different parameters as samples A, B, C and D respectively.
Fig. 4 shows the variation of average surface microhardness with depth from the surface of Inconel 718 melted with Speed (at 500 mm/min, 750 mm/min, and 1000 mm/min). From Fig. 4. It may be noted that the average surface hardness increases with depth up to a certain depth (200 to 300 micron) and then decreases to substrate microhardness. Attainment of maximum surface hardness in region below the surface is attributed to coarsening of microstructure at near the surface region as compared to below surface region. Both the microhardness of the surface and subsurface zone were found to vary with process parameters. In this regard it may be noted that a maximum microhardness at the surface and subsurface region is achieved when melting was conducted at an applied scan speed of 500 mm/min. and minimum hardness were observed for the samples processed with scan speed of 750 mm/min. Than improved microhardness in melted zone as compared to as received substrate is attributed to possibly grain refinement due to surface melting [9-11]. 3.5 Fretting Wear Study Fig. 5(a-c) show the variation of (a) wear depth as a function of interaction time (b) coefficient of friction as function of interaction time (c) summary of wear rate for all the samples. From fig. 5 (a), it may be noted that there is reduction in the wear rate follows two different kinetics. The initial faster kinetics followed by slower kinetics a later stage.it may further be noted that the kinetics of initial stage of wear (which is evident from the slope of wear depth vs time graph) the same for both as received and electron beam melted Inconel 718. However, the duration of initial faster kinetics varied with the processing condition of sample. For as received Inconel 718 the second stage of wear also follows linear kinetics. However, the kinetics of wear (rate of change of wear depth with time) is slower in the second stage as compared with first stage in Inconel 718. Followed by second stage of wear, the wear rate is almost remains negligible (there is no change in wear depth with time). For electron beam melted samples processed with 500 mm/min and 1000 mm/min, scan speed shows the initial faster kinetics for a little longer duration than as received Inconel 718 and thereafter the wear rate remains negligible. On the other hand, electron beam melted surface processed with 750 mm/min shows faster kinetics at the initial stage for shorter duration as compared to that of unmelted Inconel 718. For a shorter duration and then it decreases but followed linear kinetics up to 600 second of interaction time and become negligible thereafter. From Fig. 5(a) it may further be noted that due to electron beam surface melting there is improvement in wear resistance in terms of maximum depth of wear under steady state as compared to as received Inconel 718. A detailed study of variation of coefficient of friction with time shows that there is sharp rise in coefficient of friction at the initial stage followed by with it remains same in as received Inconel 718 for a certain period of time followed with it
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reduce to a very low value. Initial rise in coefficient of friction is as received Inconel 718 is attributed to mechanical interlocking between the mating surfaces following with there is damage of interlock coins because sliding motion and its subsequent damage causing the worn out debris occupying the space between the mating surfaces and changing the mode wear from two body wear to three body wear. For other electron beam melted samples Inconel 718 to the coefficient of friction increases to a very high value at the initial stage. However, the intermediate constant coefficient of friction value is missing. At a later stage there is drop in coefficient of friction and remains constant thereafter. A detailed study of average wear rate of all samples show that a minimum wear rate is observed samples electron beam melted with 500 mm/min [12].
Figure 5 (a) Kinetics of wear in terms of cumulative depth of wear as a function of time (b) coefficient of friction as function of time and (c) Wear rate for as received and Electron beam melted Inconel 718 at different parameters as A, B, C and D respectively.
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Figure 6 (a-d) shows the Scanning electron micrograph of worned scar of (a) as received Inconel 718 (b) electron beam melted Inconel 718 and the same at high magnification, (c) As received Inconel 718 and (d) electron beam melted Inconel. .
To understand the mechanism of wear a detailed study on microstructures of the worn-out debris were performed. The scanning electron micrographs of the worn out surface of as received and melted Inconel 718 have been presented in Figs. 6(a) - (d). The figures clearly depict the presence of micro cracks with fine scratches along with presence of micro-deformation band. Presence of micro cracks and fine scratches are due to high stress fretting wear in addition to abrasive wear acting on the surface. A closed comparison of the worned out surfaces of as received Inconel 718 with the melted surface shows that. Fig. 6(a-d) show the scanning electron micrograph of worned scar of as received Inconel 718 (b) electron beam melted Inconel 718 and the same at high magnification, (c) As received Inconel 718 and (d) electron beam melted Inconel. A comparison between Figures 4(a) and 4(b) Shows that there is no significant change in the dimension of worn scar in EB melted Inconel 718 as compared to as received Inconel 718. The high magnification view of the same shows that there is presence of microgrooves, micro cracks, and micro deformation from the surface. The groove formation is the signature of adhesive wear micro cracks are visible because of application of high stress during wear and micro deformation region are due to fretting motion. On the other hand, electron beam melted Inconel 718 shows worned surface of electron beam melted Inconel 718 shows discontinuous nature of worned region micro roughening of the surface because accumulation of worned debris and its adhesion of the surface. 4. Conclusions In this study the electron beam surface melting of Inconel 718 has been successfully performed and its effects on microstructure and wear behavior has been analyzed and following conclusion can be made: • Electron beam melting is basically used to refine the microstructures and also eliminate the precipitates by its dissolution in the matrix. Dendritic grain structures and was reported in which heterogeneous grain nucleation at the substrate melt interface is dominant. • Electron beam melting of Inconel 718 at varying parameters like scan speed showed improved surface roughness. After melting surface rippling takes place on surface and surface tension increases. The average microhardness of Electron beam melted alloy increases for every enhanced scan speed. • XRD Analysis of the electron beam surface melted seam broadly marked the presence of austenitic γ – Ni, precipitated and γ’ Ni3(Al,Ti). • Electron beam melted samples processed with 500 mm/min and 1000 mm/min, scan speed shows the initial faster kinetics for a little longer duration than as received Inconel 718 and thereafter the wear rate remains negligible
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Sumit K. Sharma et al. / Procedia Manufacturing 35 (2019) 866–873 Author name / Procedia Manufacturing 00 (2019) 000–000
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Electron beam melted samples Inconel 718 to the coefficient of friction increases to a very high value at the initial stage. However, the intermediate constant coefficient of friction value is missing. At a later stage there is drop in coefficient of friction and remains constant thereafter. Worn surface of electron beam melted Inconel 718 shows discontinuous nature of worn region micro roughening of the surface because accumulation of worn debris and its adhesion of the surface.
Acknowledgement Author is highly grateful for the partial financial support from the Board of Nuclear Science (BRNS). References [1]
K. Zhao, Y. H. Ma, L. H. Lou, and Z. Q. Hu, “Abnormal precipitation behavior of Ni3Al phase,” Mater. Sci. Eng. A, vol. 480, no. 1–2, pp. 205–208, 2008.
[2]
G. Di Girolamo, M. Alfano, L. Pagnotta, a. Taurino, J. Zekonyte, and R. J. K. Wood, “On the early stage isothermal oxidation of APS CoNiCrAlY coatings,” J. Mater. Eng. Perform., vol. 21, no. 9, pp. 1989–1997, 2012.
[3]
Soumyabrata Basak, Sumit K. Sharma, and J. Dutta Majumdar, “Studies on electron beam surface melting of AISI 316 stainless steel and AISI 347 stainless steel, procedia manufacturing 7 (2016) 647-653.
[4]
Soumitra Kumar Dinda, Md. Basiruddin Sk, Gour Gopal Roy, and Prakash Srirangam “Microstructure and mechanical properties of electron beam welded dissimilar steel to Fe-Al alloy joints,” Materials Science & Engineering A, Vol. 677, pp 182-192, 2016
[5]
J. D. Majumdar and I. Manna, “Laser surface alloying of copper with chromium II . Improvement in mechanical properties,” vol. 268, pp. 227–235, 1999.
[6]
J. D. Majumdar and I. Manna, “Laser surface alloying of AISI 304-stainless steel with molybdenum for improvement in pitting and erosion – corrosion resistance,” vol. 267, pp. 50–59, 1999.
[7]
A. D. Patel and Y. V Murty, “Effect of Cooling Rate on Microstructural Development in Alloy 71 8,” Superalloys 718, 625 Var. Deriv., pp. 123–132, 2001.
[8]
C. Zonglin, W. Shaogang, and L. I. Weihong, “! 850 8,” vol. 6, pp. 769–771, 1997.
[9]
J. Kim, J. Kim, E. Kang, and H. Wook, “Applied Surface Science Surface modification of the metal plates using continuous electron beam process ( CEBP ),” Appl. Surf. Sci., vol. 311, pp. 201–207, 2014.
[10]
K. Mumtaz and N. Hopkinson, “Top surface and side roughness of Inconel 625 parts processed using selective laser melting,” Rapid Prototyp. J., vol. 15, no. 2, pp. 96–103, 2009.
[11]
Y. Tian, D. Tomus, P. Rometsch, and X. Wu, “Influences of processing parameters on surface roughness of Hastelloy X produced by selective laser melting,” Addit. Manuf., vol. 13, pp. 103–112, 2017.
[12]
Subhasisa Nath, Sisa Pityana, Jyotsna Dutta Majumdar, “Laser surface alloying of aluminium with WC+Co+NiCr for improved wear resistance,” Surface & Coatings Technology 206 (2012) 3333–3341