Analytical and Numerical Modeling of Hot Machining of Inconel 718

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1 Amerian Journal of Mehanial and Materials Engineering 2017; 1(2): doi: /j.ajmme Analytial and Numerial Modeling of Hot Mahining of Inonel 718 Asit Kumar Parida Mehanial Engineering Department, National Institute of Tehnology Rourkela, Odisha, India address: To ite this artile: Asit Kumar Parida. Analytial and Numerial Modeling of Hot Mahining of Inonel 718. Amerian Journal of Mehanial and Materials Engineering. Vol. 1, No. 2, 2017, pp doi: /j.ajmme Reeived: Marh 13, 2017; Aepted: April 8, 2017; Published: June 2, 2017 Abstrat: The omparison of an analytial and numerial method to alulate the plasti strain, shear angle, and hip tool ontat length in hot mahining of Inonel 718 using flame heating has been disussed in the present study. The workpiee was heated with the ombination of liquid petroleum gas along with oxygen gas. Merhant analytial model has been utilized for alulation of plasti strain, shear angle, while Sutter model is used for hip-tool ontat length. DEFORM software has been used to find out the hip-tool ontat length (L), shear angle (φ ), shear strain ( ε ) in the numerial model. It was observed that shear angle and hip tool ontat length inreased and plasti strain dereased with the inrease of utting speed and feed rate. From the numerial study, a good orrelation was found for shear angle, hip tool ontat length with the analytial model. Keywords: FEM, Plasti Strain, Inonel 718, Shear Angle, Chip-Tool Contat Length 1. Introdution Nikel-base alloys are widely applied nowadays due to its mehanial harateristis (high strength, orrosion resistane, exellent reep, and fatigue strength at high temperature), it s the alloy with more appliability among all nikel base alloys. Thus these alloys are widely used in jet engines, steam generators, gas turbines and nulear reators [1]. But the alloy has a hard abrasive partile in the mirostruture, low thermal ondutivity, and low elasti modulus whih makes diffiult during mahining operations [2]. In all manufaturing proess, mahining is the vital role for making the produt. It s a material with poor mahinability and has proven wide researh on mahining of these hard materials. The hot mahining proess is being used for mahining hard materials, where maintaining tool wears redution less is extremely importane. It presents several advantages besides high material removal rates, enhanes tool life, inreases hip-tool ontat length, better surfae finish as well [3]. In hot mahining, the appliation of external heat is imposed to the surfae of the workpiee. So an inrease of temperature at utting zone softens the material, allowing for better removal rate, less utting fore, and tool wear. However, this is possible for optimum heating temperature on the workpiee. Otherwise, rapid tool wear and damage to the surfae of the workpiee oured. Other heating methods like eletri ar heating, indution heating [4], plasma [5], laser [6], furnae heating [7] and flame heating[8,9] et. have been used for heating the workpiee. However due to high ost, skilled labour and large spae requirement newly developed heating method like plasma, laser et. are not widely used in mahining industries, although these tehniques are seure. All heating methods have some benefits and some disadvantages aording to their usages [10]. The material deformation is a great influene on the plasti strain rate and temperature. From the past literature, it is mentioned that the adiabati shear band formation along with shear loalization ours at high strain rate whereas slip or twinning mehanism ours deformation at Low strain rate. The disloation motion of partile within the lattie over a wide range of utting temperature and strain rate are the mehanism of plasti deformation [11]. The hip formation and deformation mehanism of a material depend on upon the hardness of the material and the plasti strain rate inrease with the inrease of utting speed reported by duan et al. [12]. The auray of determination of plasti strains in mahining operation depends on upon the distortion of grids

Amerian Journal of Mehanial and Materials Engineering 2017; 1(2): 49-57 50 [13]. Effet of nose radius on utting fore and proess variables in hot mahining studied by Parida et al.

Chip-tool ontat phenomena our when the hip is flow on the of rake surfae of the tool. Chip-tool ontat length defined the shear angle, undeformed hip thikness [15].

2 Amerian Journal of Mehanial and Materials Engineering 2017; 1(2): [13]. Effet of nose radius on utting fore and proess variables in hot mahining studied by Parida et al. [14] using DEFORM software. They stated that inrease of nose radius derease the shear angle and inrease the hip thikness value. Chip-tool ontat phenomena our when the hip is flow on the of rake surfae of the tool. Chip-tool ontat length defined the shear angle, undeformed hip thikness [15]. A lot of work has been done on the hip-tool ontat length of the utting tool. It was found from the literature review that almost all model of the hip-tool interfae does not depend on upon the utting veloity. Zadshakoyan and Pourmostaghimi et al. [16] analysed the signifiant effet of hip-tool ontat length on various mahining responses using geneti algorithms. They stated that the derease of utting temperature and utting fore is due to a derease of hip-tool ontat length, whih further derease the seondary shear zone. Using different utting speed, Iqbal et al. [17] studied the hip-tool ontat length of two different material i.e. AISI 1045 and Ti-6A-l4V. The size of heat transfer zone in the utting zone affeted by the hip-tool ontat length. They observed that with the inreasing of utting speed, the ontat length derease in the ase of AISI 1045 but, tool-hip ontat length inreases with the inrease of utting speed. The use of flame heating on mahining of hard materials studied by different researhers [8, 18, 9, 19, 20] and different model has been used for utting fore, tool wear, surfae roughness. But the researh on plasti strain, hip-tool ontat length and shear angle has lak behind. Further, author best knowledge, less work has been studied numerially in hot mahining area. The aim is to study the behavior (shear angle, hip-tool ontat length, and plasti strain) of Inonel 718 steel in hot mahining and predited values shows good orrelation with the analytial results. 2. Experimental Proedure The experimental trials were arried out with the help of enter lathe of 6 hp spindle power and maximum spindle speed of 1200 rpm. Inonel 718 was hosen as sample material having diameter 50 mm and length of 300 mm. The hardness was around HRC as reeived from the supplier. The hemial omposition of the sample material is shown (Table 1). Unoated arbide tool was used for all experiment. The speifiation of utting tool geometry, utting ondition and physial properties of Inonel 718 are tabulated in Table 2 and Table 3 respetively. The workpiee was heated using liquefied petroleum gas (LPG) and ombined with oxygen. The workpiee was heated to 600 C temperature as the yield strength of Inonel 718 dereases at this temperature studied in past literature [21 23]. The workpiee was drilled and bored with boring tool up to 47 mm and orthogonal mahining onditions were performed. Table 1. Chemial omposition of Inonel 718(weight%) [24]. Ni Fe Cr Nb Mo Ti Al C S Table 2. Speifiation of utting tool geometry and utting ondition. Workpiee material Cutting tool material Inonel 718 Cemented arbide Rake angle -6 Clearane angle 6 Prinipal utting edge angle 75 Nose radius 0.4 mm Mahining ondition Cutting speed 60, 100 m/min Feed rate 0.1, 0.15 mm/rev Depth of ut 0.5 mm Environment Heating temperature of 600 C Table 3. Mehanial and Physial Properties of Inonel 718 [25]. Density [kg/m 3 ] 8200 Latent heat of melting [J/kg] 250,000 Solidus temperature [K] 1528 Liquidus temperature [K] 1610 Speifi heat apaity 600 Thermal ondutivity [W/m.k] at 1500 K 30 Poisson s ratio 0.3 Figure 1. Experimental setup for hot mahining [a] Optial mirosope [b]. The experiments were arried out with utting veloity of m/min, the feed of mm/rev and 0.5 mm onstant depth of ut. After eah run, the hips were olleted and hip thikness, hip-tool ontat length were measured with the help of nikon toolmaker s mirosope. The experimental setup and Nikon tool maker mirosope is shown in Figure Analytial Model Merhant theory is used to alulate the plasti strain, shear angle, hip thikness ratio in this study and Sutter model is used for hip-tool ontat length alulation. The hip thikness ratio (r) an be alulated as t r = (1) t where t is hip thikness and t is the unut hip thikness and an be alulated as t = f *sin γ (2) where f is feed rate and γ is the prinipal utting angle. The shear angle (φ ) in the shear plane an be alulated as

3 51 Asit Kumar Parida: Analytial and Numerial Modeling of Hot Mahining of Inonel 718 osα φ tan = r sinα where α is the rake angle. The plasti strain ( ε ) an be alulated as 2 1+ r 2r sin (3) α ε = (4) r osα os( 6) φ = tan = tan (0.31) = sin( 6) *3.1*sin( 6) ε = = *os( 6) 0 L L = 1.92t 0.09t (5) = 1.92* *0.3 = mm 4. Finite Element Analysis in Hot Mahining Operation The finite element analysis in hot turning operation has arried out with DEFORM software, supplied by Sientifi Forming Tehnologies Corporation (SFTC) is used in this work. The software ontains metal utting, metal forming, heat treatment, mahining distortion, in both two and three dimensions. Chip-tool ontat length ( L ) an be alulated as per Sutter et al. [26] Figure 2. Meshing and boundary onditions. In hot mahining simulation, a ylindrial heat exhange window was used to exhange heat in the proess. The heat exhange window moves along the utting diretion and maintain temperature (600 C in the ase of hot mahining) set by the user and another surfae kept at room temperature. The blak arrow mark indiates heat transfer to the environment while the other surfae whih is far away from the utting zone maintains room temperature. No movement of the workpiee along y-diretion was marked by blak triangle, while for utting tool both x and y-diretion was onstraint represented by the red triangle as shown in Figure 2. The workpiee was modeled as plasti with 30,000 elements, whereas tool was modeled as rigid with 20,000 elements. For better aurate result of plasti strain, temperature distribution, the utting zone area was assigned with high mesh density with minimum element size 2µm. Johnson-ook material modeling was implemented, a wellknown and widely used by many researhers [27].. m n ε T T r σ = { A + Bε } 1 + C ln 1. ε T 0 m Tr (6) and T is the temperature of the workpiee material. A, B, C are the yield strength, hardening modulus, and strain rate sensitivity oeffiient, n is the hardening oeffiient and m is the thermal softening oeffiient. The Johnson-Cook material onstants are tabulated in Table 4. Table 4. Johnson-ook material onstant [28]. A [MPa] B [MPa] n C m In the present study, onstant shear frition model is used in the simulation and value of shear frition fator (m) was taken 0.9 [29] as Eq.7. m τ = (7) k where τ = Shear stress, k = shear flow stress of the work material Damage riteria have been implemented using Cokroft and Latham model, as Inonel 718 is low thermal ondutivity material and hip segmentation nature and evaluated as Eq.8. where σ is the flow stress,. ε is the plasti strain,. ε is the plasti strain rate,. ε 0 is the referene plasti strain rate. T m is the melting point of the material, T r is the room temperature ε f σ C = σ d ε i 0 σ (8)

4 Amerian Journal of Mehanial and Materials Engineering 2017; 1(2): where C i is the ritial damage [28], ε f is the strain at the breaking onditions, ε is the effetive strain, σ is the effetive stress and σ is the maximum stress. For modeling of hot mahining of a heat exhange window was used to exhange heat in a loal area whih is available in DEFORM software. The total power input, through the window an be expressed as [30] Eq.9. q = ha( T T ) (9) window workpiee where, A is the surfae area of heat exhange window (desribed as red ylinder), h is the heat onventional oeffiient, T window is the temperature of the heat exhange window and T workpiee is the temperature of the workpiee. The detail work plan is shown in Figure 3. Figure 3. Detail work plans in this study. 5. Results and Disussion The simulated results (plasti strain, shear angle, hip-tool ontat length) obtained in DEFORM software at different mahining onditions were validated with different analytial model (Merhant and Sutter) Shear Angle The omputed shear angle at different utting ondition is shown in Figure 4. It was notied that with an inrease of utting speed and feed rate the shear angle inrease. The shear angle at utting onditions of 60 (m/min)/0.1 (mm/rev) and 100 (m/min)/0.15 (mm/rev) were overestimated from the analytial result, whereas at 100 (m/min)/0.1 (mm/rev) utting ondition it was underestimated from the analytial result. At 60 m/min and 0.15 mm/rev utting ondition, the shear angle was good agreement between the numerial and analytial result as shown in Figure 5. The inrease of shear angle is the sign of the redution of utting fore during hot mahining. Figure 4. Shear angle at different utting onditions.

5 53 Asit Kumar Parida: Analytial and Numerial Modeling of Hot Mahining of Inonel 718 Figure 5. Comparison between the simulated and analytial shear angle at different utting onditions Plasti Strain As workpiee material is suffered by both thermal softening and redution of frition due to an inrease of utting speed from m/min, the plasti strain at V=60 m/min (3.65) is redued to at V=100 m/min (2.7) in the analytial method. But at a onstant speed, with an inrease of feed rate (0.1 to 0.15 mm/rev) the plastis strain dereased from (3.65 to 2.74). Exept at V=100 m/min and f=0.10 mm/rev, the numerial plasti strain value was overestimated ompared to the analytial result. The numerial plasti strain at different utting onditions is shown in Figure 6. The omparison between the simulated and analytial model for plasti strain result as shown in Figure 7. Figure 6. Numerial plasti strain distribution in the workpiee and hip at different utting onditions.

6 Amerian Journal of Mehanial and Materials Engineering 2017; 1(2): Figure 7. Comparison between the simulated and analytial plasti strain value at different utting onditions Chip-Tool Contat Length Iqbal et al. [17] studied the ontat tool-hip length using finite element simulation of mahining of steel. They used a different model for ontat length and Marino's model was the best result for turning of AISI 1045 steel. They stated that frition fator has a big role in hip-tool ontat length. During hot mahining (600 C), the frition between the hip-tool dereased ompared to room temperature mahining. The hip-tool ontat length measurement in the simulation is shown in Figure 8. It was observed that with an inrease of utting speed and feed rate the hip-tool ontat length inreased. The inrease of hip-tool ontat length has many benefit like normal stress ating on the tool beomes lower and improve tool life [3]. The analytial result finds lose agreement with the simulation results. Chip-tool ontat length in simulation and experiment are shown in Figure 9 and Figure 10 respetively. The omparison between the analytial, simulation and experiment hip-tool ontat length results (Figure 11). The analytial and predited shear angle, hip-tool ontat length, plasti strain values are tabulated in Table 5. The error % between the experiment and simulated value were alulated using Eq.9 and tabulated in Table 6. Figure 8. Chip-tool ontat length in simulation.

7 55 Asit Kumar Parida: Analytial and Numerial Modeling of Hot Mahining of Inonel 718 Error = Experimental value Simulated value 100% Experimental value Figure 9. Simulation and optial view of hip-tool ontat length at different utting ondition. (10)

8 Amerian Journal of Mehanial and Materials Engineering 2017; 1(2): Mahining onditions V=60m/min, V=100m/min Figure 10. Comparison between the Numerial, Analytial, and Experimental hip-tool ontat length. Table 5. Calulated and Predited shear angle, plasti strain, and hip-tool ontat length. Analytial plasti strain Simulated plasti strain Analytial shear angle ( ) Simulated shear angle ( ) Analytial hip-tool ontat length f =0.10 mm/rev f =0.15 mm/rev f =0.10 mm/rev f =0.15 mm/rev Simulated hiptool ontat length The Comparison between analytial and simulated values for shear angle, plasti strain, hip tool ontat length at hot mahining and its error perentage is tabulated in Table 4. The error % of plasti strain was higher at utting speed of 60 m/min and feed rate of 0.15 mm/rev, for the shear angle at 100(m/min)/0.10(mm/rev) and for hip-tool ontat length at 60(m/min)/0.1(mm/rev) utting ondition respetively. Table 6. Errors perentage between the analytial and simulated onditions. Mahining onditions V=60m/min, f =0.10 mm/rev V=60m/min, f =0.15 mm/rev V=100m/min, f =0.10 mm/rev V=100m/min, f=0.15 mm/rev 6. Conlusions Plasti strain (%) Shear angle (%) Chip-tool ontat length (%) In this present work, hot mahining of Inonel 718 has been studied using the gas flame heating method. An analytial studied has been arried out using Merhant and Sutter model to find out plasti strain, shear angle, and hiptool ontat length. Numerial analysis was also arried out to study the strain, shear angle and hip-tool ontat length using DEFORM software at different utting onditions (both room and heated). Numerial modeling and simulation of mahining proess variables has advantage that it provides possibilities to simulate the mahining proess. The input data and boundary onditions is the main riteria for auray. The model is verified with the analytial model data of hip tool ontat length, shear angle, plasti strain. From the analysis, it was observed that the plasti strain value dereased, Shear angle and hip-tool ontat length value inreased with inrease of utting speed and feed rate. The maximum error % between the experimental and simulation for plasti strain was observed at utting onditions of v=60m/min, f=0.10mm/rev, for shear angle 19.6% error at v=100m/min, f=0.10 mm/rev and for hip-tool ontat length 22% error at v=60m/min, f=0.10mm/rev respetively. Referenes [1] Ezugwu EO. High speed mahining of aero-engine alloys. J Brazilian So Meh Si Eng 2004;26:1 11. doi: /s [2] Ezugwu EO. Key improvements in the mahining of diffiultto-ut aerospae superalloys. Int J Mah Tools Manuf 2005;45: doi: /j.ijmahtools [3] Nurul Amin AKM, Ginta TL. Heat-Assisted Mahining. vol doi: /b

9 57 Asit Kumar Parida: Analytial and Numerial Modeling of Hot Mahining of Inonel 718 [4] Ginta TL, Amin AKMN. Thermally-assisted end milling of titanium alloy Ti-6Al-4V using indution heating. Int J Mah Mah Mater 2013;14: doi: /ijmmm [5] Hinds BK, Almeida SM. Plasma ar heating for hot mahining. Int J Mah Tool Des Res 1981;21: doi: / (81) [6] Patten JA, Ghantasala M, Shayan AR, Poyraz HB, Ravindra D. Miro-Laser Assisted Mahining (µ-lam): Srath Tests on 4H-SiC [7] Pal DK, Basu SK. Hot mahining of austeniti manganese steel by shaping. Int J Mah Tool Des Res 1971;11: doi: / (71) [8] Parida AK, Maity KP. An experimental investigation to optimize multi-response harateristis of Ni-hard material using hot mahining. Adv Eng Forum 2016;16: doi: / [9] Maity KP, Swain PK. An experimental investigation of hotmahining to predit tool life. J Mater Proess Tehnol 2008;198: doi: /j.jmatprote [10] Lei S, Pfefferkorn F. A review of thermally assisted mahining. ASME Int Conf Manuf Si Eng (MSEC 2007) 2007: doi: /msec [11] Davim JP, Maranh C. A study of plasti strain and plasti strain rate in mahining of steel AISI 1045 using FEM analysis. Mater Des 2009;30: doi: /j.matdes [12] Duan CZ, Wang MJ, Pang JZ, Li GH. A alulational model of shear strain and strain rate within shear band in a serrated hip formed during high speed mahining. J Mater Proess Tehnol 2006;178: doi: /j.jmatprote [13] Ghadbeigi H, Bradbury SR, Pinna C, Yates JR. Determination of miro-sale plasti strain aused by orthogonal utting. Int J Mah Tools Manuf 2008;48: doi: /j.ijmahtools [14] Parida AK, Maity KP. Effet of nose radius on fores, and proess parameters in hot mahining of Inonel 718 using finite element analysis. Eng Si Tehnol an Int J 2016:4 10. doi: /j.jesth [15] Toropov A, Ko SL. Predition of tool-hip ontat length using a new slip-line solution for orthogonal utting. Int J Mah Tools Manuf 2003;43: doi: /s (03)00155-x. [16] Zadshakoyan M, Pourmostaghimi V. Cutting tool rater wear measurement in turning using hip geometry and geneti programming. Int J Appl Metaheuristi Comput 2015;6: doi: /ijam [17] Iqbal SA, Mativenga PT, Sheikh MA. A omparative study of the tool-hip ontat length in turning of two engineering alloys for a wide range of utting speeds. Int J Adv Manuf Tehnol 2009;42: doi: /s [18] Parida AK, Maity KP. Finite element method and experimental investigation of hot turning of Inonel 718. Adv Eng Forum 2016;16: doi: / [19] Parida AK, Maity KP. Optimization of multi-responses in hot turning of Inonel 625 alloy using DEA-Taguhi approah. Int J Eng Res Afria 2016;24: doi: / [20] Parida AK, Maity KP. Optimization in hot turning of nikel based alloy using desirability funtion analysis. Int J Eng Res Afria 2016;24: doi: / [21] Sun S, Brandt M, Dargush MS. Thermally enhaned mahining of hard-to-mahine materialsa review. Int J Mah Tools Manuf 2010;50: doi: /j.ijmahtools [22] Leshok CE, Kim JN, Shin YC. Plasma enhaned mahining of Inonel 718: Modeling of workpiee temperature with plasma heating and experimental results. Int J Mah Tools Manuf 2001;41: doi: /s (00) [23] Novak JW, Shin YC, Inropera FP. Assessment of plasma enhaned mahining for improved mahinability of Inonel 718. J Manuf Si Eng 1997;119:125. doi: / [24] Shi B, Attia H, Vargas R, Tavakoli S. Numerial and experimental investigation of laser-assisted mahining of Inonel 718. Mah Si Tehnol 2008;12: doi: / [25] Yilbas BS, Akhtar SS, Karatas C. Laser surfae treatment of Inonel 718 alloy: Thermal stress analysis. Opt Lasers Eng 2010;48: doi: /j.optlaseng [26] Sutter G. Chip geometries during high-speed mahining for orthogonal utting onditions. Int J Mah Tools Manuf 2005;45: doi: /j.ijmahtools [27] Joshi S, Tewari A, Joshi SS. Mirostrutural haraterization of hip segmentation under different Mahining environments in orthogonal mahining of Ti6Al4V. J Eng Mater Tehnol 2015;137: doi: / [28] Uhlmann E, Von Der Shulenburg MG, Zettier R. Finite element modeling and utting simulation of inonel 718. CIRP Ann - Manuf Tehnol 2007;56:61 4. doi: /j.irp [29] Özel T, Ulutan D. Predition of mahining indued residual stresses in turning of titanium and nikel based alloys with experiments and finite element simulations. CIRP Ann - Manuf Tehnol 2012;61: doi: /j.irp [30] Singh G, Teli M, Samanta A, Singh R, Singh G, Teli M,. Finite element modeling of laser-assisted mahining of AISI D2 tool steel. Materials and Manufaturing engineering, 2015;6914. doi: /

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