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Experimental Investigation on Work Hardening and Residual Stress during Machining of Inconel718
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 5 (2018) 13301–13308
www.materialstoday.com/proceedings
ICMMM - 2017
Experimental Investigation on Work Hardening and Residual Stress during Machining of Inconel718 Anthony Xavior M1, Arnaud Duchosal 2, Jeyapandiarajan P3* 1Professor, 2,3Assistant Professor 1&3Manufacturing Department, School of Mechanical Engineering, VIT University, Vellore - 632014, India. 2 LMR - CEROC, Université François Rabelais de Tours, 7 avenue Marcel Dassault, 37200 TOURS, France
Abstract The influence of machining / turning under different cutting conditions with different tool materials on residual stresses and work hardening of Inconel718 super alloy has been investigated. Turning process was performed using three different tool materials namely Carbide, Ceramic and cBN with constant tool geometry under three different cutting environments such as Dry machining, MQL and flood cooling cutting condition. Taguchi's L18 orthogonal array was used for the design of experiments and the machining trails were conducted accordingly. Machining induced residual stresses were measured and analysed by using Xray diffraction measurement technique. Microhardness on surface and subsurface was measured by using Vickers microhardness tester. An attempt has been made to understand the correlation between work hardening and residual stresses induced during turning of Inconel 718. © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).
Keywords:Aluminium alloys; Ceramic reinforcements; Tensile strength; Heat treatment.
1. Introduction Materials properties play a significant role in manufacturing industry for selection fabrication of components/equipment in aerospace and automobile sector. Inconel 718 is one of the important nickel base alloy which possesses superior mechanical and thermal properties such as high strength and toughness, high creep and corrosion resistance and retains high strength at elevated temperatures [1]. Difficulties during machining of Inconel 718 super alloy are due to its high shear strength, low thermal conductivity, high chemical affinity and formation of *Corresponding author. Tel.:+918870756512 E-mail address: [email protected] 2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).
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build-up edges. Due to these characteristics Inconel 718 comes under the category of difficult to machine materials[2]. In turning operation, the work material is exposed to mechanical, thermal and sometimes chemical loading that can lead to strain aging, recrystallization and plastic deformation. Due to plastic deformation and strain aging, the materials hardness and brittleness might increase and recrystallization might cause the material to become soften with increased ductility. There mechanical (stress, strain and pressure) and thermal (high temperature and rapid quenching) effects are the primary reasons for microstructure alteration, generation of residual stresses, phase transformation and work hardening effect [3]. It has been observed that the depth and degree of microstructure alteration depends on cutting parameters and cutting conditions [4], and also depends on tool condition and tool geometry [5]. After work material is being machined, it’s surface or subsurface up to 5-10µm depth shows different behaviour than interior subsurface, this particular layer is known as white layer, which generally possesses fine nano-crystalline structure. This layer is found to be 10-15% harder than bulk the material [3]. Magnitude of plastic deformation near machined surface and degree of work hardened layer increases with increasing cutting velocity or tool wear, also tensile residual stresses decreases with increase in cutting speed and tool wear [6]. Machining of Inconel 718 is characterized by increase in stress, strain rate and temperatures at cutting zone, as a result there is an alteration in metallurgical and mechanical properties [7]. Carbide tools are still largely used for turning of super alloys especially for Nickel base alloys. This tool material gives better surface quality, high material removal rate and adequate tool life. From the literatures, maximum cutting speed range is limited up to 120m/min for this material [8]. Apart from this many researchers has reported that advanced tool materials such as ceramic and cBN were shown better performance at higher cutting speed up to 250m/min but cost of such tools limits the engineering application [9]. In this current research work, an attempt has been made to understand the quantum of induced stresses and the work hardening nature on the surface and sub-surface of the machined specimen of Inconel718 work material. 2. Material and experimental method 2.1 Experimental Setup Computer Numerical Control (CNC) turning machine as shown in Fig.-1 was used for experimentations on Inconel718 alloy. The machining is carried out for three sets of cutting conditions such as Dry machining, minimum quantity lubrication (MQL -80ml/hr, ester oil) and flood cooling cutting condition (coolant flow rate – 100 litre/hr, semi synthetic water soluble oil). The experiments were conducted according to Taguchi’s L18 orthogonal array design with different cutting parameters with three different types of tool material such as PVD AlTiN Carbide (KU25 grade) insert, Ceramic Insert (KY4300 grade) and cBN insert (KB1630), supplied by Kennametal. The work material used for experimentation is Inconel 718 nickel based super alloy; the chemical composition is 55%Ni, 17%Cr, 3.05% Mo, 1%Co, 0.35%Si, 0.35%Mn, 0.80%C, 0.60%Al, 0.90%Ti, 0.30%Cu, 0.015%P, 0.006%B and Balance Fe. Table–1 shows cutting parameters, conditions and their levels considered for experimentations in this research work. Table 1: Cutting parameters/levels/conditions S.No
Parameters
Level1
Level2
Level3
1.
Cutting speed (Vc)
60
100
-
2.
Tool (Insert) material
Carbide
Ceramic
cBN
3.
Cutting condition
Dry
MQL
Flood cooling
Anthony Xavior M et al. / Materials Today: Proceedings 5 (2018) 13301–13308
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Fig.1. Experimental Setup on CNC Lathe Machine
2.2 Experimental observations. Subsequent to experiments, machined specimens were sectioned in to small pieces with Wire EDM process for further data measurement and analysis. Microhardness of machined samples were measured by using Vickers microhardness tester. For residual stress data collection X-ray diffraction measurement were performed on machined samples. In this work Brukers D8 DISCOVER XRD unit with sin2ψ measurement technique was used. The parameters used in XRD measurement are shown in Table – 2. The residual stresses measured from surface to subsurface layers by removing succeeding layer from machined surface up to depth of 180micron. The electro polishing method was used to remove layers in order to avoid reintroduction of additional residual stresses. Table-3 shows L18 orthogonal array with experimental conditions and their corresponding observations. Table–2 Parameters used in XRD analysis Young’s modulus Poisons ratio Bragg’s angle (2θ) Oscillations during measurement Collimator spot size
203Gpa 0.284 1510 50 2mm
3. Result and Discussion High cutting forces, tool wear, selection of cutting parameters and conditions are the major factors considered for plastic deformation [11]. Plastic deformation causes hardening of machined work piece layer which is also known as work hardening effect and also plastic deformation induces more residual stresses due to excessive plastic strain [10]. Presence of carbide precipitate in microstructure ensures increased hardness of work piece; carbide precipitate is due to high temperature generation in work material, also high temperature contributes towards the generation of tensile residual stresses [12].
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Anthony Xavior M et al. / Materials Today: Proceedings 5 (2018) 13301–13308 Table -3. Detailed L18 Orthogonal Array and Experimental Observations Sr. No
Cutting Speed (m/min)
Cutting Cond.
Tool Material
Surface Microhardness (HV)
Surface Residual Stress (Mpa)
1
60
Dry
Carbide
383.7
523.6
2
60
Dry
Ceramic
303.1
591.2
3
60
Dry
cBN
361.7
413.7
4
60
MQL
Carbide
324.5
542.8
5
60
MQL
Ceramic
363.5
486.3
6
60
MQL
cBN
341.3
326.1
7
60
Flood
Carbide
395.9
724.6
8
60
Flood
Ceramic
348.6
587.2
9
60
Flood
cBN
369.4
378.4
10
100
Dry
Carbide
420.1
716.4
11
100
Dry
Ceramic
344.5
780.0
12
100
Dry
cBN
400.6
596.0
13
100
MQL
Carbide
364.2
748.0
14
100
MQL
Ceramic
401.9
670.0
15
100
MQL
cBN
379
487.0
16
100
Flood
Carbide
435.9
949.9
17
100
Flood
Ceramic
386.8
804.1
18
100
Flood
cBN
411.4
556.0
Fig. 2 (a, b & c) shows the plot drawn between the mirco-hardness measured at various subsurface depth on the machined specimen. From the figures it is understood that the microhardness on the periphery of the machined specimen is highest and gradually decreases towards the subsurface. Further it is also observed that dry machining using carbide insert with 100m/min cutting speed resulted in higher hardness throughout the depth when compared to the specimen machined under other cutting conditions. During the machining process, the work material is subjected to a reasonably more cutting temperature and cutting pressure, which affects the fundamental behaviour of the material. Moreover, the softening process of the subsurface region can be characterized by the effect of ageing on micro hardness. The machined surface subjected to high cutting temperature during machining process is similar to the ageing process. Therefore, it could be a fact that the instability or alteration of microstructure in the form of plastic deformation caused by the heat generated during machining leads to the softening of the sub-surface. During machining, the surface and immediate subsurface of the material become harder due to work hardening.
Anthony Xavior M et al. / Materials Today: Proceedings 5 (2018) 13301–13308
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(a)
Fig.2 (a ,b and c) Microhardness analysis during machining of Inconel718 under different cutting parameters and cutting conditions
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Fig. 3 (a, b and c) Residual stress profile after turning/machining of Inconel 718 with different cutting parameters, tool materials and conditions.
Anthony Xavior M et al. / Materials Today: Proceedings 5 (2018) 13301–13308
13307
Residual stresses are present in almost all machined materials and product forms. They can be a major factor for the failure of the component, particularly those subjected to alternating service loads or corrosive environments. Surface residual stresses are either tensile or compressive in nature. Residual stresses in given component are the cumulative effect of stresses generated due to mechanical effects, thermal effects and chemical effects. All mechanical based manufacturing processes induce mechanically generated residual stresses in the component. Fig. 3(a, b and c) shows the graphs drawn between the measured residual stresses against the subsurface depth. It is being understood that on the periphery the observed stresses are tensile for all the machining conditions. As the subsurface depth increases the stresses become compressive for certain depth and ultimately reaches the neutral value after a depth of about 300µm. A minimum of 413.7 Mpa tensile stress on the periphery was observed during dry machining with cBN tool at 60m/min cutting speed and maximum stress of 949.9 Mpa was observed while machining under flood cooling with carbide insert at a cutting speed of 100 m/min. Fig 4(a) and (b) shows the micrograph of the work material subjected to machining under various conditions.
4(a) Surface of In718 after machining at a cutting speed of 100m/min using carbide insert
4(b) Surface of In718 after machining at a cutting speed of 100m/min using cBN insert
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4. Conclusion Work hardening effect and residual stress generation during turning of inconel718 have been analysed. Some metallurgical changes observed in microstructural analysis, along with varying residual stresses and microhardness profiles were observed, some of the important conclusions established from this work are listed below. - In dry cutting condition at a cutting speed (Vc = 100m/min) more work hardening, high metallurgical damage and high tensile residual stresses on machined surface were found. - In flood cooling cutting condition highest microhardness and pure compressive residual stresses were noticed
-
In MQL cutting condition with cutting speed (Vc = 100m/min), small metallurgical damage, low microhardness and less compressive residual stresses were observed.
References [1] Bushlya V, Zhou J, Ståhl JE. Effect of cutting conditions on machinability of superalloy Inconel 718 during high speed turning with coated and uncoated PCBN tools. Procedia CIRP. 2012 Dec 31;3:370-5. [2] Yazid MZ, CheHaron CH, Ghani JA, Ibrahim GA, Said AY. Surface integrity of Inconel 718 when finish turning with PVD coated carbide tool under MQL. Procedia Engineering. 2011 Jan 1;19:396-401. [3] Ulutan D, Ozel T. Machining induced surface integrity in titanium and nickel alloys: a review. International Journal of Machine Tools and Manufacture. 2011 Mar 31;51(3):250-80. [4] Sharman AR, Hughes JI, Ridgway K. Workpiece surface integrity and tool life issues when turning Inconel 718™ nickel based superalloy. Machining science and technology. 2004 Dec 30;8(3):399-414. [5] Sridhar BR, Devananda G, Ramachandra K, Bhat R. Effect of machining parameters and heat treatment on the residual stress distribution in titanium alloy IMI-834. Journal of Materials Processing Technology. 2003 Aug 20;139(1):628-34. [6] Peng RL, Zhou J. Surface integrity and the influence of tool wear in high speed machining of Inconel 718. InICF13 2013 Oct 22. [7] Chen Z, Peng RL, Moverare J, Avdovic P, Zhou JM, Johansson S. Surface Integrity and Structural Stability of Broached Inconel 718 at High Temperatures. Metallurgical and Materials Transactions A. 2016 Jul 1;47(7):3664-76. [8] Satyanarayana B, Janardhana GR, Rao DH. Experimental Investigations for Optimized High Speed Turning on Inconel 718 using Taguchi method based Grey Relational Analysis. [9] Borse SC. Predicting Surface Roughness, Tool Wear and MMR in Machining Inconel 718: A Review. [10] Kenda J, Pusavec F, Kopac J. Analysis of residual stresses in sustainable cryogenic machining of nickel based alloy—Inconel 718. Journal of manufacturing science and engineering. 2011 Aug 1;133(4):041009. [11] Sharman AR, Hughes JI, Ridgway K. Surface integrity and tool life when turning Inconel 718 using ultra high pressure and flood coolant systems. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture. 2008 Jun 1;222(6):653-64. [12] Chen Z, Peng RL, Avdovic P, Zhou J, Moverare J, Karlsson F, Johansson S. Effect of thermal exposure on microstructure and nano-hardness of broached Inconel 718. InMATEC Web of Conferences 2014 (Vol. 14, p. 08002). EDP Sciences.
ScienceDirect Materials Today: Proceedings 5 (2018) 13301–13308
www.materialstoday.com/proceedings
ICMMM - 2017
Experimental Investigation on Work Hardening and Residual Stress during Machining of Inconel718 Anthony Xavior M1, Arnaud Duchosal 2, Jeyapandiarajan P3* 1Professor, 2,3Assistant Professor 1&3Manufacturing Department, School of Mechanical Engineering, VIT University, Vellore - 632014, India. 2 LMR - CEROC, Université François Rabelais de Tours, 7 avenue Marcel Dassault, 37200 TOURS, France
Abstract The influence of machining / turning under different cutting conditions with different tool materials on residual stresses and work hardening of Inconel718 super alloy has been investigated. Turning process was performed using three different tool materials namely Carbide, Ceramic and cBN with constant tool geometry under three different cutting environments such as Dry machining, MQL and flood cooling cutting condition. Taguchi's L18 orthogonal array was used for the design of experiments and the machining trails were conducted accordingly. Machining induced residual stresses were measured and analysed by using Xray diffraction measurement technique. Microhardness on surface and subsurface was measured by using Vickers microhardness tester. An attempt has been made to understand the correlation between work hardening and residual stresses induced during turning of Inconel 718. © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).
Keywords:Aluminium alloys; Ceramic reinforcements; Tensile strength; Heat treatment.
1. Introduction Materials properties play a significant role in manufacturing industry for selection fabrication of components/equipment in aerospace and automobile sector. Inconel 718 is one of the important nickel base alloy which possesses superior mechanical and thermal properties such as high strength and toughness, high creep and corrosion resistance and retains high strength at elevated temperatures [1]. Difficulties during machining of Inconel 718 super alloy are due to its high shear strength, low thermal conductivity, high chemical affinity and formation of *Corresponding author. Tel.:+918870756512 E-mail address: [email protected] 2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).
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Anthony Xavior M et al. / Materials Today: Proceedings 5 (2018) 13301–13308
build-up edges. Due to these characteristics Inconel 718 comes under the category of difficult to machine materials[2]. In turning operation, the work material is exposed to mechanical, thermal and sometimes chemical loading that can lead to strain aging, recrystallization and plastic deformation. Due to plastic deformation and strain aging, the materials hardness and brittleness might increase and recrystallization might cause the material to become soften with increased ductility. There mechanical (stress, strain and pressure) and thermal (high temperature and rapid quenching) effects are the primary reasons for microstructure alteration, generation of residual stresses, phase transformation and work hardening effect [3]. It has been observed that the depth and degree of microstructure alteration depends on cutting parameters and cutting conditions [4], and also depends on tool condition and tool geometry [5]. After work material is being machined, it’s surface or subsurface up to 5-10µm depth shows different behaviour than interior subsurface, this particular layer is known as white layer, which generally possesses fine nano-crystalline structure. This layer is found to be 10-15% harder than bulk the material [3]. Magnitude of plastic deformation near machined surface and degree of work hardened layer increases with increasing cutting velocity or tool wear, also tensile residual stresses decreases with increase in cutting speed and tool wear [6]. Machining of Inconel 718 is characterized by increase in stress, strain rate and temperatures at cutting zone, as a result there is an alteration in metallurgical and mechanical properties [7]. Carbide tools are still largely used for turning of super alloys especially for Nickel base alloys. This tool material gives better surface quality, high material removal rate and adequate tool life. From the literatures, maximum cutting speed range is limited up to 120m/min for this material [8]. Apart from this many researchers has reported that advanced tool materials such as ceramic and cBN were shown better performance at higher cutting speed up to 250m/min but cost of such tools limits the engineering application [9]. In this current research work, an attempt has been made to understand the quantum of induced stresses and the work hardening nature on the surface and sub-surface of the machined specimen of Inconel718 work material. 2. Material and experimental method 2.1 Experimental Setup Computer Numerical Control (CNC) turning machine as shown in Fig.-1 was used for experimentations on Inconel718 alloy. The machining is carried out for three sets of cutting conditions such as Dry machining, minimum quantity lubrication (MQL -80ml/hr, ester oil) and flood cooling cutting condition (coolant flow rate – 100 litre/hr, semi synthetic water soluble oil). The experiments were conducted according to Taguchi’s L18 orthogonal array design with different cutting parameters with three different types of tool material such as PVD AlTiN Carbide (KU25 grade) insert, Ceramic Insert (KY4300 grade) and cBN insert (KB1630), supplied by Kennametal. The work material used for experimentation is Inconel 718 nickel based super alloy; the chemical composition is 55%Ni, 17%Cr, 3.05% Mo, 1%Co, 0.35%Si, 0.35%Mn, 0.80%C, 0.60%Al, 0.90%Ti, 0.30%Cu, 0.015%P, 0.006%B and Balance Fe. Table–1 shows cutting parameters, conditions and their levels considered for experimentations in this research work. Table 1: Cutting parameters/levels/conditions S.No
Parameters
Level1
Level2
Level3
1.
Cutting speed (Vc)
60
100
-
2.
Tool (Insert) material
Carbide
Ceramic
cBN
3.
Cutting condition
Dry
MQL
Flood cooling
Anthony Xavior M et al. / Materials Today: Proceedings 5 (2018) 13301–13308
13303
Fig.1. Experimental Setup on CNC Lathe Machine
2.2 Experimental observations. Subsequent to experiments, machined specimens were sectioned in to small pieces with Wire EDM process for further data measurement and analysis. Microhardness of machined samples were measured by using Vickers microhardness tester. For residual stress data collection X-ray diffraction measurement were performed on machined samples. In this work Brukers D8 DISCOVER XRD unit with sin2ψ measurement technique was used. The parameters used in XRD measurement are shown in Table – 2. The residual stresses measured from surface to subsurface layers by removing succeeding layer from machined surface up to depth of 180micron. The electro polishing method was used to remove layers in order to avoid reintroduction of additional residual stresses. Table-3 shows L18 orthogonal array with experimental conditions and their corresponding observations. Table–2 Parameters used in XRD analysis Young’s modulus Poisons ratio Bragg’s angle (2θ) Oscillations during measurement Collimator spot size
203Gpa 0.284 1510 50 2mm
3. Result and Discussion High cutting forces, tool wear, selection of cutting parameters and conditions are the major factors considered for plastic deformation [11]. Plastic deformation causes hardening of machined work piece layer which is also known as work hardening effect and also plastic deformation induces more residual stresses due to excessive plastic strain [10]. Presence of carbide precipitate in microstructure ensures increased hardness of work piece; carbide precipitate is due to high temperature generation in work material, also high temperature contributes towards the generation of tensile residual stresses [12].
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Anthony Xavior M et al. / Materials Today: Proceedings 5 (2018) 13301–13308 Table -3. Detailed L18 Orthogonal Array and Experimental Observations Sr. No
Cutting Speed (m/min)
Cutting Cond.
Tool Material
Surface Microhardness (HV)
Surface Residual Stress (Mpa)
1
60
Dry
Carbide
383.7
523.6
2
60
Dry
Ceramic
303.1
591.2
3
60
Dry
cBN
361.7
413.7
4
60
MQL
Carbide
324.5
542.8
5
60
MQL
Ceramic
363.5
486.3
6
60
MQL
cBN
341.3
326.1
7
60
Flood
Carbide
395.9
724.6
8
60
Flood
Ceramic
348.6
587.2
9
60
Flood
cBN
369.4
378.4
10
100
Dry
Carbide
420.1
716.4
11
100
Dry
Ceramic
344.5
780.0
12
100
Dry
cBN
400.6
596.0
13
100
MQL
Carbide
364.2
748.0
14
100
MQL
Ceramic
401.9
670.0
15
100
MQL
cBN
379
487.0
16
100
Flood
Carbide
435.9
949.9
17
100
Flood
Ceramic
386.8
804.1
18
100
Flood
cBN
411.4
556.0
Fig. 2 (a, b & c) shows the plot drawn between the mirco-hardness measured at various subsurface depth on the machined specimen. From the figures it is understood that the microhardness on the periphery of the machined specimen is highest and gradually decreases towards the subsurface. Further it is also observed that dry machining using carbide insert with 100m/min cutting speed resulted in higher hardness throughout the depth when compared to the specimen machined under other cutting conditions. During the machining process, the work material is subjected to a reasonably more cutting temperature and cutting pressure, which affects the fundamental behaviour of the material. Moreover, the softening process of the subsurface region can be characterized by the effect of ageing on micro hardness. The machined surface subjected to high cutting temperature during machining process is similar to the ageing process. Therefore, it could be a fact that the instability or alteration of microstructure in the form of plastic deformation caused by the heat generated during machining leads to the softening of the sub-surface. During machining, the surface and immediate subsurface of the material become harder due to work hardening.
Anthony Xavior M et al. / Materials Today: Proceedings 5 (2018) 13301–13308
13305
(a)
Fig.2 (a ,b and c) Microhardness analysis during machining of Inconel718 under different cutting parameters and cutting conditions
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Fig. 3 (a, b and c) Residual stress profile after turning/machining of Inconel 718 with different cutting parameters, tool materials and conditions.
Anthony Xavior M et al. / Materials Today: Proceedings 5 (2018) 13301–13308
13307
Residual stresses are present in almost all machined materials and product forms. They can be a major factor for the failure of the component, particularly those subjected to alternating service loads or corrosive environments. Surface residual stresses are either tensile or compressive in nature. Residual stresses in given component are the cumulative effect of stresses generated due to mechanical effects, thermal effects and chemical effects. All mechanical based manufacturing processes induce mechanically generated residual stresses in the component. Fig. 3(a, b and c) shows the graphs drawn between the measured residual stresses against the subsurface depth. It is being understood that on the periphery the observed stresses are tensile for all the machining conditions. As the subsurface depth increases the stresses become compressive for certain depth and ultimately reaches the neutral value after a depth of about 300µm. A minimum of 413.7 Mpa tensile stress on the periphery was observed during dry machining with cBN tool at 60m/min cutting speed and maximum stress of 949.9 Mpa was observed while machining under flood cooling with carbide insert at a cutting speed of 100 m/min. Fig 4(a) and (b) shows the micrograph of the work material subjected to machining under various conditions.
4(a) Surface of In718 after machining at a cutting speed of 100m/min using carbide insert
4(b) Surface of In718 after machining at a cutting speed of 100m/min using cBN insert
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Anthony Xavior M et al. / Materials Today: Proceedings 5 (2018) 13301–13308
4. Conclusion Work hardening effect and residual stress generation during turning of inconel718 have been analysed. Some metallurgical changes observed in microstructural analysis, along with varying residual stresses and microhardness profiles were observed, some of the important conclusions established from this work are listed below. - In dry cutting condition at a cutting speed (Vc = 100m/min) more work hardening, high metallurgical damage and high tensile residual stresses on machined surface were found. - In flood cooling cutting condition highest microhardness and pure compressive residual stresses were noticed
-
In MQL cutting condition with cutting speed (Vc = 100m/min), small metallurgical damage, low microhardness and less compressive residual stresses were observed.
References [1] Bushlya V, Zhou J, Ståhl JE. Effect of cutting conditions on machinability of superalloy Inconel 718 during high speed turning with coated and uncoated PCBN tools. Procedia CIRP. 2012 Dec 31;3:370-5. [2] Yazid MZ, CheHaron CH, Ghani JA, Ibrahim GA, Said AY. Surface integrity of Inconel 718 when finish turning with PVD coated carbide tool under MQL. Procedia Engineering. 2011 Jan 1;19:396-401. [3] Ulutan D, Ozel T. Machining induced surface integrity in titanium and nickel alloys: a review. International Journal of Machine Tools and Manufacture. 2011 Mar 31;51(3):250-80. [4] Sharman AR, Hughes JI, Ridgway K. Workpiece surface integrity and tool life issues when turning Inconel 718™ nickel based superalloy. Machining science and technology. 2004 Dec 30;8(3):399-414. [5] Sridhar BR, Devananda G, Ramachandra K, Bhat R. Effect of machining parameters and heat treatment on the residual stress distribution in titanium alloy IMI-834. Journal of Materials Processing Technology. 2003 Aug 20;139(1):628-34. [6] Peng RL, Zhou J. Surface integrity and the influence of tool wear in high speed machining of Inconel 718. InICF13 2013 Oct 22. [7] Chen Z, Peng RL, Moverare J, Avdovic P, Zhou JM, Johansson S. Surface Integrity and Structural Stability of Broached Inconel 718 at High Temperatures. Metallurgical and Materials Transactions A. 2016 Jul 1;47(7):3664-76. [8] Satyanarayana B, Janardhana GR, Rao DH. Experimental Investigations for Optimized High Speed Turning on Inconel 718 using Taguchi method based Grey Relational Analysis. [9] Borse SC. Predicting Surface Roughness, Tool Wear and MMR in Machining Inconel 718: A Review. [10] Kenda J, Pusavec F, Kopac J. Analysis of residual stresses in sustainable cryogenic machining of nickel based alloy—Inconel 718. Journal of manufacturing science and engineering. 2011 Aug 1;133(4):041009. [11] Sharman AR, Hughes JI, Ridgway K. Surface integrity and tool life when turning Inconel 718 using ultra high pressure and flood coolant systems. Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture. 2008 Jun 1;222(6):653-64. [12] Chen Z, Peng RL, Avdovic P, Zhou J, Moverare J, Karlsson F, Johansson S. Effect of thermal exposure on microstructure and nano-hardness of broached Inconel 718. InMATEC Web of Conferences 2014 (Vol. 14, p. 08002). EDP Sciences.