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The effects of different types of welding current on the characteristics of nickel aluminum bronze using gas metal arc welding
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 5 (2018) 9535–9542
www.materialstoday.com/proceedings
The 10th Thailand International Metallurgy Conference (The 10th TIMETC)
The effects of different types of welding current on the characteristics of nickel aluminum bronze using gas metal arc welding Suttipong Sriintharasuta,*, Bovornchok Poopatb, Isaratat Phung-onc a
Production Engineering Department, Faculty of Engineering King Mongkut’s University of Technology Thonburi, Bangkok, Thailand b Department of Production Engineering, Welding Engineering Program, Faculty of Engineering, King Mongkut’s University of Technology Thonburi, Bangkok, Thailand c Maintenance Technology Center, Institute for Scientific and Technological Research and Services (ISTRS) King Mongkut’s University of Technology Thonburi, Bangkok, Thailand
Abstract This study aims to investigate the effects of different types of welding current on the characteristics of Nickel Aluminum Bronze Alloy (NAB) such as microstructure, hardness, depth/width ratio and dilution by using Gas Metal Arc Welding (GMAW). The mechanized GMAW was employed for the bead on plate welding of NAB using 3 levels of heat input, 500-600 J/mm, 700-800 J/mm. and 800-900 J/mm with 2 types of welding current: standard and pulsed. The AWS.A5.7 ERCuNiAl solid wire and 100% argon shielding gas were applied. The results indicated that welding current types did not significantly affect the microstructures in the weld area and heat affected zone (HAZ).The hardness of welding from both welding current types were comparable with the average hardness of 160-180 HV in weld metal and 200-240 HV in the HAZ. Nevertheless the more heat per unit length (HI) was the higher depth/width ratio was. However, for pulsed current, the metal was transfer form solid wire to the NAB during the peak current of pulsed current resulting in deeper penetration but with higher dilution ratio compared to standard current. This could indicate that the pulsed current could be more appropriated for groove welding while the standard current for the built-up overlay welding. © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of The 10th Thailand International Metallurgy Conference. Keywords: Nickel aluminum bronze; Standard current; Pulsed current
* Corresponding author. Tel.: +66 2 470 9011. E-mail address: [email protected] 2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of The 10th Thailand International Metallurgy Conference.
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Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
1. Introduction Nickel Aluminum Bronze (NAB) is a copper base alloy that are developed from aluminum bronze alloys by adding the element such as nickel (Ni), aluminums (Al), iron (Fe) [1]. Aluminum content would result for high strength and formation with oxide to be Aluminum oxide (Al2O) that can improve the corrosion resistance. Nickel and Iron were added to improve specifications of NAB in regard with corrosion resistant and tensile strength, respectively [2]. NAB is the metallurgical complex alloys with several intermetallic phases such as alpha (α), beta (β), and kappa phase (κ) [2].The α is a copper rich phase with FCC structure, β is the CuAl, and kappa phase (κ) is the intermetallic compound which have possible 4 types figures: κi, κii, κiii, κiv [1]. The κi is the Fe3Al phase having shape likely the rosette while κii has the same composition but it mostly presents along the grain boundaries of α. κiii is the eutectoid phase which is likely to be lamellar and κiv is the phase of Fe3Al but its look like in the fine globular at the α phase interior. NAB owns high strength, high toughness, good corrosion resistant and corrosion fatigue [3] suitable for use in equipment for the marine application such as pump, valve and propeller blade. The ranges of NAB have many usages depending their chemical compositions and properties. To be specific, NAB no.C95800 is widely used in the marine industry. [1]. It is one of the best corrosion resistance materials in sea water and has the typical composition of Ni4.5%,Fe 4.0%,Al9.0%,Mn 1.2% and Cu 81.3% by %weight according to ASTM B148-97[4]. Due to its properties and complication in manufacturing making it to be very expensive, reducing cost and extended service life by welding repair would be preferred. However, NAB alloy is very difficult to weld due to its high thermal conductivity and thermal expansion compared to steels [5]. In addition, it usually has weldability problems such as porosity, hot cracking and distortion [6]. Therefore the appropriate welding parameters would be required when performing the repair of NAB. Pulse MIG welding is one variation of GMAW process with a non-contact transfer between the electrode and the weld puddle. This process works by forming one droplet of molten metal at the tip of the solid wire per pulse. This uses just the right amount of current added to push one droplet across the arc into weld puddle. By using this technique, the average current would be decreased resulting in lower heat input. This would be helpful for reducing the weld distortion as well as metallurgic effects. In this study, the standard and pulsed current would be used to perform the bead on plate weld on NAB at the same average heat input. Weld bead profile, hardness, as well as microstructures would be examined. 2. Experimentation 2.1. Materials and methods The cast NAB (C95800) plate were used in this research with composition (by % weight): 9.26 % Al, 3.26% Ni, 2.55%Fe, 0.22%Mn and Cu as balance. Specimens were 125 x 250 mm with 25 mm thickness. The mechanized GMAW was employed for the bead on plate welding using 3 levels of heat input, 500-600 J/mm, 700-800 J/mm. and 800-900 J/mm with 2 types of welding current: standard and pulsed. The welding speed was fixed at 400 mm/min and 100% argon shielding was employed. The welding wire was 1.2 mm ERCuNiAl with chemical compositions of 9.50% Al, 4.00%Ni, 3.50% Fe, 0.60% Mn and Cu as balance.The sequence of welding and process parameter are shown in the Table 1. Table 1. Process parameter employ in the study (the average current from welding machine). Peak Pulse Frequency Welding Current Voltage Base current time Current mode current (Hz) (A ) (V) Standard
185
19.1
Ip (A)
Ib (A)
tp
-
-
-
Welding speed (mm/min)
Gas flow rate
Heat input (J/mm)
(l/min) -
-
13
530.025
Standard
215
21.8
-
-
-
-
-
13
703.050
Standard
240
24.3
-
-
-
-
-
13
874.800
Pulse
155*
23.3
100
180
2.3
50
400
13
541.725
Pulse
185*
25.4
120
200
2.3
50
400
13
704.850
Pulse
210*
17.4
140
220
2.3
50
400
13
863.100
Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
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2.2. Macrostructure and microstructure studies Cross sections of the weld beads were covered all weld zones (Base metals- Heat affected zone -Weld metal) for weld bead profile and microstructure examination. The specimens were prepared by using sandpaper of 80-1000 grit and etched using 5g ferric (III) chloride and 30 ml hydrochloric acid dissolved in 100 ml distilled water. The macrographs were analyzed with the DM (Digital Microscopy). For microstructure examination, the samples were prepared by using sandpaper of 80-2000 grit followed by 0.3 micron alumina and etched with 5g ferric (III) chloride and 30 ml hydrochloric acid 60 ml dissolved in ethanol (95%). The specimens were examined for the microstructure in weld metal and HAZ using the OM (Optical Microscopy) and SEM (Scanning Electron Microscope). 2.3. Measurement of hardness Vicker micro-hardness testing was used to analyze the mechanical characterization of the specimens in the area of the weld metal and interface zone. A load of 500 kgf and dwell time of 10 s was employed. The measurement started at the fusion boundary and progressed to its top and bottom at 10 points each with the distance between points of 250 um as shown in Fig 1.
Fig. 1. Measurement of micro hardness test.
3. Result and discussion 3.1. Macrostructure examination The macrograph of the cross section is presented in Fig 2 and Fig 3. The fusion zone and adjacent were free of defect. For both standard and pulsed current, the higher heat input resulted in wider and deeper weld bead profile. The depth to width ratio and dilution ratio (the ratio between area of base metal melted and amount of area of filler melted with area of base metal melted) were also increased as the heat input increased. Those were the results from higher heat that got into the specimens as well as more electromagnetic force from higher welding current used in higher heat input. In addition, it can be seen that the weld bead profles were different between pulsed and standard current. Standard current provided wider bead while pulsed current resulted in deeper penetration. These were due to the fact that in pulsed current the metal transfer occurred during the peak current having higher electromagnetic force to push the weld pool deeper as well as the pinching force on the transferred droplets [7]. However, due to the deeper penetration of pulsed current, it resulted in calculated dilution ratio in which the standard current had less dilution. These implied that the standard current could be possibly more suitable for welding in build-up or overlay. In constrast, the pulsed current would be suitable for making a groove weld. 3.2. Microstructure examination The micrographs of weld metal of NAB are presented in Fig 4 for each lever of heat input. Both types of welding current modes showed comparable microstructures consisted of the alpha phase () as matrix and beta ()
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Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
Fig. 2. Macrograph of weld metal and measurement profile of weld bead with Standard current (a.) 500-600 J/mm. (b.) 700-800 J/mm. (c.) 800900 J/mm; Pulse current (d.) 500-600 J/mm. (e.) 700-800 J/mm (f.) 800-900 J/mm.
Fig. 3. The relation of characteristics of weld bead as function of range of heat input.
Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
9539
as the martensitic (dark area). The microstructural features were finer as the heat input increased. This was possible due the decomposition of the features from higher heat and slower cooling. For closer look, the features of pulsed current were slightly finer compared to the standard current. However, this did not affect the mechanical property, hardness, significantly. From macrostructure of weld bead profile, the width of interface area and heat affected zone (HAZ) were very narrow for all specimens. However, in microscopic, the microstructure underwent significant changes in this area [8]. As shown in Fig 5, the weld interfaces showed the phase of alpha (), intermetallic kappa () and retained beta (Retained ) in HAZ. Retained beta (’) was the martensitic structure which from the partial distintegration of phase due to the rapid cooling rate (lower than 1 celcious/sec) [1] resulting in some ofwas still remained. In the same way as in weld zone, the HAZ at the interface also had the comparable microstructure for both standard and pulsed current in every step of heat input. This was due the fact that both types of current were fixed at the same calculated heat input resulting in comparable cooling rate at the interface. Therefore, the metallurgical changes in these areas would be not significantly different.
Fig. 4. Micrograph of weld metal Heat input 500-600 J/mm. (a) Standard current (b) Pulsed current; Heat input 700-800 J/mm. (c) Standard current (d) pulsed current; Heat input 800-900 J/mm. (e) Standard current (f) Pulsed current.
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Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
Fig. 5. SEM micrograph of the interface zone in range of heat input 500-600 J/mm (a) Standard current (b) Pulsed current; Heat input 700-800 J/mm (c) Standard current (d) Pulsed current; heat input 800-900 J/mm (e) Standard current (f) Pulsed current.
3.3. Measurement of hardness The result of micro hardness test of the specimens with standard current and pulse current mode are show in Fig 6. The average hardness in the weld area of both welding current modes is 160-180 HV and 200-240 HV in the HAZ. The hardness of weld metal was slightly higher than that of the base metal due to higher elements of iron (Fe) aluminum (Al) and nickel (Ni) in filler wire. However, the hardness in HAZ was higher than weld metal and base metal because this area had the retained (martensitic ) and phase. From the hardness profile for both current types which were comparable, it indicated that the types of current did not affect the heat input, since they were kept comparable, resulting in comparable cooling rate. Therefore, both hardness and microstructure from both current types were not significantly affected.
Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
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Fig. 6. Micro hardness profile in the cross section as the function of distance from fusion boundary; (a) heat input 500-600 J/mm (b) Heat input 700-800 J/mm (c) heat input 800-900 J/mm.
4. Conclusion From the study the effect of welding current types in GMAW, it could be drawn conclusions as the following; At the same heat input level, standard current provided wider weld bead profile while pulsed current provided deeper penetration. The higher heat input was, the deeper penetration and more dilution were. Phases presented at weld zone and HAZ for both types of welding current were comparable due to the comparable heat input and cooling rate. Hardness in HAZ from both current types was higher than base material due to microstructural changes as the formation of martensitic and phase Standard currently had less dilution ratio compared to pulsed current. This could indicate the possibly use of current types in various application Acknowledgments The authors would like to thanks Cdr.Swieng Thuanboon, the engineering officer of Royal Thai Dockyard and the Welding Evaluation and Learning Laboratory of the Maintenance Technology Center,Institute for Scientific and Technological Research and Service (ISTRS) King Mongkut’s University of Technology Thonburi for provide and suport and equipments for this experimental.
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Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
References [1] B.Thossatheppitak, S.Suranuntchai, V.Uthaisangsuk, A.Manonukul, P.Mungsuntisuk, “Microstructure Evolution of Nickel Aluminum Bronze Alloy during Compression at Elevated Temperatures”, Advance Materials Research, Vol. 893, pp.365-370, 2014. [2] B. Sabbaghzadeh, R Parvizi, A.Davoodi, M. Hadi Moayed, “Corrosion evaluation of multi-pass welded nickel-aluminum bronze alloy in 3.5% sodium chloride solution:A restorative application of gas tungsten arc welding process”,Materials and Design Vol.58,pp. 346-356,2014 [3]H. Li, D. Grudgings, N. P.Larkin, J. Norrish, M. Callaghan, “Optimization of welding parameters for repairing NiAl bronze components”, Materials Science Forum, pp.706-709 2980-2985, 2012 [4]American Society for Testing and Materials (ASTM B148-97).Standard Specification for Aluminum-Bronze Sand Casting: ASTM International, West Conshohocken, PA, 2009 [5]Copper Development Association, “Weiding of Aluminum Bronzes”,Publication No.85,1988 [6]J. Cheanvarin, “The case study of repairnig the propeller blade of H.T.M.S.Srichang”,Royal Thai Dockyard, Bangkok, 1994 [7]B.P.Agrawal, R. Kumar, “Challenges in Application of Pulse Current Gas Metal Arc Welding Process for Prepration of Weld Joint with Superior Quality”,International Journal of Engineering Research &Technology,Vol.5, pp.319-327,2016 [8]D. Ding,Z. Pan,S. van Duin,H. Li and Chen Shen, “Fabricating Superior NiAl Bronze Components through Wire Arc Additive Manufacturing”,Vol.9,Materials,2016
ScienceDirect Materials Today: Proceedings 5 (2018) 9535–9542
www.materialstoday.com/proceedings
The 10th Thailand International Metallurgy Conference (The 10th TIMETC)
The effects of different types of welding current on the characteristics of nickel aluminum bronze using gas metal arc welding Suttipong Sriintharasuta,*, Bovornchok Poopatb, Isaratat Phung-onc a
Production Engineering Department, Faculty of Engineering King Mongkut’s University of Technology Thonburi, Bangkok, Thailand b Department of Production Engineering, Welding Engineering Program, Faculty of Engineering, King Mongkut’s University of Technology Thonburi, Bangkok, Thailand c Maintenance Technology Center, Institute for Scientific and Technological Research and Services (ISTRS) King Mongkut’s University of Technology Thonburi, Bangkok, Thailand
Abstract This study aims to investigate the effects of different types of welding current on the characteristics of Nickel Aluminum Bronze Alloy (NAB) such as microstructure, hardness, depth/width ratio and dilution by using Gas Metal Arc Welding (GMAW). The mechanized GMAW was employed for the bead on plate welding of NAB using 3 levels of heat input, 500-600 J/mm, 700-800 J/mm. and 800-900 J/mm with 2 types of welding current: standard and pulsed. The AWS.A5.7 ERCuNiAl solid wire and 100% argon shielding gas were applied. The results indicated that welding current types did not significantly affect the microstructures in the weld area and heat affected zone (HAZ).The hardness of welding from both welding current types were comparable with the average hardness of 160-180 HV in weld metal and 200-240 HV in the HAZ. Nevertheless the more heat per unit length (HI) was the higher depth/width ratio was. However, for pulsed current, the metal was transfer form solid wire to the NAB during the peak current of pulsed current resulting in deeper penetration but with higher dilution ratio compared to standard current. This could indicate that the pulsed current could be more appropriated for groove welding while the standard current for the built-up overlay welding. © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of The 10th Thailand International Metallurgy Conference. Keywords: Nickel aluminum bronze; Standard current; Pulsed current
* Corresponding author. Tel.: +66 2 470 9011. E-mail address: [email protected] 2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of The 10th Thailand International Metallurgy Conference.
9536
Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
1. Introduction Nickel Aluminum Bronze (NAB) is a copper base alloy that are developed from aluminum bronze alloys by adding the element such as nickel (Ni), aluminums (Al), iron (Fe) [1]. Aluminum content would result for high strength and formation with oxide to be Aluminum oxide (Al2O) that can improve the corrosion resistance. Nickel and Iron were added to improve specifications of NAB in regard with corrosion resistant and tensile strength, respectively [2]. NAB is the metallurgical complex alloys with several intermetallic phases such as alpha (α), beta (β), and kappa phase (κ) [2].The α is a copper rich phase with FCC structure, β is the CuAl, and kappa phase (κ) is the intermetallic compound which have possible 4 types figures: κi, κii, κiii, κiv [1]. The κi is the Fe3Al phase having shape likely the rosette while κii has the same composition but it mostly presents along the grain boundaries of α. κiii is the eutectoid phase which is likely to be lamellar and κiv is the phase of Fe3Al but its look like in the fine globular at the α phase interior. NAB owns high strength, high toughness, good corrosion resistant and corrosion fatigue [3] suitable for use in equipment for the marine application such as pump, valve and propeller blade. The ranges of NAB have many usages depending their chemical compositions and properties. To be specific, NAB no.C95800 is widely used in the marine industry. [1]. It is one of the best corrosion resistance materials in sea water and has the typical composition of Ni4.5%,Fe 4.0%,Al9.0%,Mn 1.2% and Cu 81.3% by %weight according to ASTM B148-97[4]. Due to its properties and complication in manufacturing making it to be very expensive, reducing cost and extended service life by welding repair would be preferred. However, NAB alloy is very difficult to weld due to its high thermal conductivity and thermal expansion compared to steels [5]. In addition, it usually has weldability problems such as porosity, hot cracking and distortion [6]. Therefore the appropriate welding parameters would be required when performing the repair of NAB. Pulse MIG welding is one variation of GMAW process with a non-contact transfer between the electrode and the weld puddle. This process works by forming one droplet of molten metal at the tip of the solid wire per pulse. This uses just the right amount of current added to push one droplet across the arc into weld puddle. By using this technique, the average current would be decreased resulting in lower heat input. This would be helpful for reducing the weld distortion as well as metallurgic effects. In this study, the standard and pulsed current would be used to perform the bead on plate weld on NAB at the same average heat input. Weld bead profile, hardness, as well as microstructures would be examined. 2. Experimentation 2.1. Materials and methods The cast NAB (C95800) plate were used in this research with composition (by % weight): 9.26 % Al, 3.26% Ni, 2.55%Fe, 0.22%Mn and Cu as balance. Specimens were 125 x 250 mm with 25 mm thickness. The mechanized GMAW was employed for the bead on plate welding using 3 levels of heat input, 500-600 J/mm, 700-800 J/mm. and 800-900 J/mm with 2 types of welding current: standard and pulsed. The welding speed was fixed at 400 mm/min and 100% argon shielding was employed. The welding wire was 1.2 mm ERCuNiAl with chemical compositions of 9.50% Al, 4.00%Ni, 3.50% Fe, 0.60% Mn and Cu as balance.The sequence of welding and process parameter are shown in the Table 1. Table 1. Process parameter employ in the study (the average current from welding machine). Peak Pulse Frequency Welding Current Voltage Base current time Current mode current (Hz) (A ) (V) Standard
185
19.1
Ip (A)
Ib (A)
tp
-
-
-
Welding speed (mm/min)
Gas flow rate
Heat input (J/mm)
(l/min) -
-
13
530.025
Standard
215
21.8
-
-
-
-
-
13
703.050
Standard
240
24.3
-
-
-
-
-
13
874.800
Pulse
155*
23.3
100
180
2.3
50
400
13
541.725
Pulse
185*
25.4
120
200
2.3
50
400
13
704.850
Pulse
210*
17.4
140
220
2.3
50
400
13
863.100
Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
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2.2. Macrostructure and microstructure studies Cross sections of the weld beads were covered all weld zones (Base metals- Heat affected zone -Weld metal) for weld bead profile and microstructure examination. The specimens were prepared by using sandpaper of 80-1000 grit and etched using 5g ferric (III) chloride and 30 ml hydrochloric acid dissolved in 100 ml distilled water. The macrographs were analyzed with the DM (Digital Microscopy). For microstructure examination, the samples were prepared by using sandpaper of 80-2000 grit followed by 0.3 micron alumina and etched with 5g ferric (III) chloride and 30 ml hydrochloric acid 60 ml dissolved in ethanol (95%). The specimens were examined for the microstructure in weld metal and HAZ using the OM (Optical Microscopy) and SEM (Scanning Electron Microscope). 2.3. Measurement of hardness Vicker micro-hardness testing was used to analyze the mechanical characterization of the specimens in the area of the weld metal and interface zone. A load of 500 kgf and dwell time of 10 s was employed. The measurement started at the fusion boundary and progressed to its top and bottom at 10 points each with the distance between points of 250 um as shown in Fig 1.
Fig. 1. Measurement of micro hardness test.
3. Result and discussion 3.1. Macrostructure examination The macrograph of the cross section is presented in Fig 2 and Fig 3. The fusion zone and adjacent were free of defect. For both standard and pulsed current, the higher heat input resulted in wider and deeper weld bead profile. The depth to width ratio and dilution ratio (the ratio between area of base metal melted and amount of area of filler melted with area of base metal melted) were also increased as the heat input increased. Those were the results from higher heat that got into the specimens as well as more electromagnetic force from higher welding current used in higher heat input. In addition, it can be seen that the weld bead profles were different between pulsed and standard current. Standard current provided wider bead while pulsed current resulted in deeper penetration. These were due to the fact that in pulsed current the metal transfer occurred during the peak current having higher electromagnetic force to push the weld pool deeper as well as the pinching force on the transferred droplets [7]. However, due to the deeper penetration of pulsed current, it resulted in calculated dilution ratio in which the standard current had less dilution. These implied that the standard current could be possibly more suitable for welding in build-up or overlay. In constrast, the pulsed current would be suitable for making a groove weld. 3.2. Microstructure examination The micrographs of weld metal of NAB are presented in Fig 4 for each lever of heat input. Both types of welding current modes showed comparable microstructures consisted of the alpha phase () as matrix and beta ()
9538
Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
Fig. 2. Macrograph of weld metal and measurement profile of weld bead with Standard current (a.) 500-600 J/mm. (b.) 700-800 J/mm. (c.) 800900 J/mm; Pulse current (d.) 500-600 J/mm. (e.) 700-800 J/mm (f.) 800-900 J/mm.
Fig. 3. The relation of characteristics of weld bead as function of range of heat input.
Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
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as the martensitic (dark area). The microstructural features were finer as the heat input increased. This was possible due the decomposition of the features from higher heat and slower cooling. For closer look, the features of pulsed current were slightly finer compared to the standard current. However, this did not affect the mechanical property, hardness, significantly. From macrostructure of weld bead profile, the width of interface area and heat affected zone (HAZ) were very narrow for all specimens. However, in microscopic, the microstructure underwent significant changes in this area [8]. As shown in Fig 5, the weld interfaces showed the phase of alpha (), intermetallic kappa () and retained beta (Retained ) in HAZ. Retained beta (’) was the martensitic structure which from the partial distintegration of phase due to the rapid cooling rate (lower than 1 celcious/sec) [1] resulting in some ofwas still remained. In the same way as in weld zone, the HAZ at the interface also had the comparable microstructure for both standard and pulsed current in every step of heat input. This was due the fact that both types of current were fixed at the same calculated heat input resulting in comparable cooling rate at the interface. Therefore, the metallurgical changes in these areas would be not significantly different.
Fig. 4. Micrograph of weld metal Heat input 500-600 J/mm. (a) Standard current (b) Pulsed current; Heat input 700-800 J/mm. (c) Standard current (d) pulsed current; Heat input 800-900 J/mm. (e) Standard current (f) Pulsed current.
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Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
Fig. 5. SEM micrograph of the interface zone in range of heat input 500-600 J/mm (a) Standard current (b) Pulsed current; Heat input 700-800 J/mm (c) Standard current (d) Pulsed current; heat input 800-900 J/mm (e) Standard current (f) Pulsed current.
3.3. Measurement of hardness The result of micro hardness test of the specimens with standard current and pulse current mode are show in Fig 6. The average hardness in the weld area of both welding current modes is 160-180 HV and 200-240 HV in the HAZ. The hardness of weld metal was slightly higher than that of the base metal due to higher elements of iron (Fe) aluminum (Al) and nickel (Ni) in filler wire. However, the hardness in HAZ was higher than weld metal and base metal because this area had the retained (martensitic ) and phase. From the hardness profile for both current types which were comparable, it indicated that the types of current did not affect the heat input, since they were kept comparable, resulting in comparable cooling rate. Therefore, both hardness and microstructure from both current types were not significantly affected.
Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
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Fig. 6. Micro hardness profile in the cross section as the function of distance from fusion boundary; (a) heat input 500-600 J/mm (b) Heat input 700-800 J/mm (c) heat input 800-900 J/mm.
4. Conclusion From the study the effect of welding current types in GMAW, it could be drawn conclusions as the following; At the same heat input level, standard current provided wider weld bead profile while pulsed current provided deeper penetration. The higher heat input was, the deeper penetration and more dilution were. Phases presented at weld zone and HAZ for both types of welding current were comparable due to the comparable heat input and cooling rate. Hardness in HAZ from both current types was higher than base material due to microstructural changes as the formation of martensitic and phase Standard currently had less dilution ratio compared to pulsed current. This could indicate the possibly use of current types in various application Acknowledgments The authors would like to thanks Cdr.Swieng Thuanboon, the engineering officer of Royal Thai Dockyard and the Welding Evaluation and Learning Laboratory of the Maintenance Technology Center,Institute for Scientific and Technological Research and Service (ISTRS) King Mongkut’s University of Technology Thonburi for provide and suport and equipments for this experimental.
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Suttipong Sriintharasut et at./ Materials Today: Proceedings 5 (2018) 9535–9542
References [1] B.Thossatheppitak, S.Suranuntchai, V.Uthaisangsuk, A.Manonukul, P.Mungsuntisuk, “Microstructure Evolution of Nickel Aluminum Bronze Alloy during Compression at Elevated Temperatures”, Advance Materials Research, Vol. 893, pp.365-370, 2014. [2] B. Sabbaghzadeh, R Parvizi, A.Davoodi, M. Hadi Moayed, “Corrosion evaluation of multi-pass welded nickel-aluminum bronze alloy in 3.5% sodium chloride solution:A restorative application of gas tungsten arc welding process”,Materials and Design Vol.58,pp. 346-356,2014 [3]H. Li, D. Grudgings, N. P.Larkin, J. Norrish, M. Callaghan, “Optimization of welding parameters for repairing NiAl bronze components”, Materials Science Forum, pp.706-709 2980-2985, 2012 [4]American Society for Testing and Materials (ASTM B148-97).Standard Specification for Aluminum-Bronze Sand Casting: ASTM International, West Conshohocken, PA, 2009 [5]Copper Development Association, “Weiding of Aluminum Bronzes”,Publication No.85,1988 [6]J. Cheanvarin, “The case study of repairnig the propeller blade of H.T.M.S.Srichang”,Royal Thai Dockyard, Bangkok, 1994 [7]B.P.Agrawal, R. Kumar, “Challenges in Application of Pulse Current Gas Metal Arc Welding Process for Prepration of Weld Joint with Superior Quality”,International Journal of Engineering Research &Technology,Vol.5, pp.319-327,2016 [8]D. Ding,Z. Pan,S. van Duin,H. Li and Chen Shen, “Fabricating Superior NiAl Bronze Components through Wire Arc Additive Manufacturing”,Vol.9,Materials,2016