• Title/Summary/Keyword: Plasma Transferred Arc Welding

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A Study on the Characteristics of the Ni base Super Alloy Overlay Layer by Plasma Transferred Arc (PTA) Method (Ni 계 초내열합금의 PTA 오버레이 층 특성에 관한 연구)

  • Kim Young-Sik;Choi Young-Goog;Lee Kwang-Ryeol
    • Journal of Welding and Joining
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    • v.24 no.3
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    • pp.49-54
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    • 2006
  • The Plasma Transferred Arc (PTA) overlaying method is lately introduced as one of the most useful surface modification method of the engine component. In this paper, the characteristics of the Co-base and Ni-base super alloy overlay layers by PTA method were investigated through the metallurgical, abrasive and cavitation erosion test. Experimental results showed that the abrasive wear resistance of the Co-base Stellite 6 overlayer was the most superior and followed in order of Nimonic 80A, Inconel 625 and Inconel 718. However, the cavitation erosion characteristic of the Stellite 6 overlayer was the most inferior and it was better in order of Inconel 625, Inconel 718 and Nimonic 80A.

A Study on Hot Ductility Behavior of Ni-based Superalloys (니켈기 초내열합금의 고온연성거동에 관한 연구)

  • Lee, Choung-Rae;Um, Sang-Ho;Kim, Sung-Wook;Choi, Cheol;Lee, Chang-Hee
    • Journal of Welding and Joining
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    • v.22 no.2
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    • pp.59-68
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    • 2004
  • Plasma transferred arc welding (PTAW) has been taken into consideration for repairing Ni-based superalloy components used gas turbine blades. Various cracks has been generally reported to be found in the base metal heat affected zone(HAZ) along grain boundary. Thus, hot cracking susceptibility of Ni-based superalloys was evaluated according to heat treatments. Hot ductility test was conducted on specimens with solution treated at 112$0^{\circ}C$ for 2 hours and aging treated at 845$^{\circ}C$ for 24hours after solution treatment. The results of the hot ductility test appeared that solution treated specimens were the highest ductility recovery rate among three conditions. The loss of ductility at high temperature in Ni-based superalloy was mainly controlled by the degree of pain boundary wetting due to constitutional liquation of MC carbide precipitates. Meanwhile, the highest ductility recovery rate in solution-treated alloys seems to be lack of M23C6, which can be dissolved during heating and then result in the local enrichment of Cr in the vicinity of the grain boundary.

The Experimental Research On The Electrical Characteristics For The Ignition Of Plasma Jet Using The Advance Discharge Of High Frequency Voltage With Attenuation (감쇠파 고주파전압의 선행방전을 이용한 Plasma jet의 전기적 기동특성에 대한 실험적 연구)

  • Choon Saing Jhoun
    • 전기의세계
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    • v.21 no.4
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    • pp.27-38
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    • 1972
  • This paper discusses the characteristics about the ignition of D.C. main discharge is a plasma jet generator, manufactured for trial as non-transferred type, when the electrical energy appropriate to the ignition is supplied to the gap between the electrodes by using advance discharge of attenuating high frequency voltage generated by a high frequency oscillator with mercury spark gap. These characteristics are under the influences of (a) the length of mercury gap in high frequency oscillator and the quantity of hydrogen flow supplied to it, (b) the condenser capacity of the high frequency oscillator circuit, (c) the length of plasma jet torch in D.C. main discharge circuit and the quantity of argon flow supplied to it, (d) the circuit constants of D.C. main discharge circuit. The results for these characteristics, obtained by this research, are considered to be helpful to the designs for the ignition of a plasma jet as well as the welding arc stabilizer by high frequency discharge and the high frequency arc welder.

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A Study on the Abrasive Wear Properties of the PTA Overlay Layers using the Super Alloy Powder (초내열합금분말에 의한 PTA 오버레이부의 연삭 마모 특성 연구)

  • Kim, Young-Sik;Choi, Young-Gook;Lim, Chang-Hoon;Kim, Jong-Do
    • Journal of Welding and Joining
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    • v.27 no.3
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    • pp.80-84
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    • 2009
  • The Plasma Transferred Arc (PTA) overlay welding method is lately introduced as one of the most useful surface overlay method of the engine component. In this paper, the overlay welding on the SNCrW heat resisting alloy was conducted by the PTA overlay welding process using the super alloy powder. The characteristics of the overlay layers were investigated through the metallurgical and abrasive test. Experimental results showed that the overlay on the SNCrW heat resisting alloy surface was successfully made without hot cracking. The friction wear characteristics of the Co-base Stellite 6 overlayer were most superior. However the abrasive wear characteristics were most inferior in the Co-base Stellite 6 overlayer.

Effect of dilution on micro hardness of Ni-Cr-B-Si alloy hardfaced on austenitic stainless steel plate for sodium-cooled fast reactor applications

  • Balaguru, S.;Murali, Vela;Chellapandi, P.;Gupta, Manoj
    • Nuclear Engineering and Technology
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    • v.52 no.3
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    • pp.589-596
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    • 2020
  • Many components in the assembly section of Sodium-cooled Fast Reactor are made of good corrosionresistant 316 LN Stainless Steel material. To avoid self-welding of the components with the coolant sodium at elevated temperature, hardfacing is inevitable. Ni-based colmonoy-5 is used for hardfacing due to its lower dose rate by Plasma Transferred Arc process due to its low dilution. Since Ni-Cr-B-Si alloy becomes very fluidic while depositing, the major height of the weld overlay rests inside the groove. Hardfacing is also done over the plain surface where grooving is not possible. Therefore, grooved and ungrooved hardfaced specimens were prepared at different travel speeds. Fe content at every 100 ㎛ of the weld overlay was studied by Energy Dispersive Spectroscopy and also the micro hardness was determined at those locations. A correlation between iron dilution from the base metal and the micro hardness was established. Therefore, if the Fe content of the weld overlay is known, the hardness at that location can be obtained using the correlation and vice-versa. A new correlation between micro hardness and dilution coefficient is obtained at different locations. A comparative study between those specimens is carried out to recommend the optimum travel speed for lower dilution.

A Study on Relationship between Hot Ductility Behavior and Hot Cracking Susceptibility in PTA Weld of Ni-based Superalloy (니켈기 초내열합금 PTA용접부의 고온균열감수성과 고온연성거동에 관한 연구)

  • Lee, Chung-Rae;Kim, Sung-Wook;Choi, Woo-Hyuk;Eom, Sang-Ho;Lee, Chang-Hee;Kim, Jae-Chul;Choi, Chul
    • Proceedings of the KWS Conference
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    • 2003.05a
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    • pp.40-42
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    • 2003
  • In general, nickel-base superalloy has been extensively used as land-based gas turbine blades and vanes. Plasma transferred arc welding(PTAW) has been considered as a repair welding process of nickel-base superalloy. This research evaluated the relationship between hot ductility behavior and hot cracking susceptibility in nickel-base superalloys. Ductility recovery rate of nickel base superalloys was found to be poor due to incipient melting and constitutional liquation. This seems to increase the hot cracking susceptibility.

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The Effect of Current and Preheat Temperature on Structure and Hardness of Stellite 12 Alloy Overlayer by PTA Process (PTA법에 의한 스텔라이트 12 합금 육성층의 조직과 경도에 미치는 전류와 예열온도의 영향)

  • Jung, B.H.;Kim, M.G.;Kim, G.D.;Kim, M.Y.;Lee, S.Y.
    • Journal of the Korean Society for Heat Treatment
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    • v.13 no.4
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    • pp.246-252
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    • 2000
  • Stellite 12 alloy-powder was overlaid on 410 stainless steel valve seat using plasma transferred arc(PTA) process. Variation of characteristic of microstructure and hardness of deposit with current(90~150 A) and preheat temperature(R.T.~$400^{\circ}C$) was investigated. Important conclusion obtained are as follows; All welding conditions used produced a sound deposit layer with no defect in single pass welding. The maximum deposit had 4.0~4.8 mm in thickness and its bead width was increased with increase of current and preheat temperature. The deposit showed hypoeutectic microstruture, which was consisting of primary cobalt dendrite and networked $M_7C_3$ type eutectic carbides. The amount of eutectic carbides was decreased and its dendritic secondary arm spacing was increased with increase of current. Hardness of the deposit was decreased with increase of current. Preheat temperature up to $400^{\circ}C$, however, showed little influence on the hardness and microstructure. The hardness was also influenced by diluted Fe content near the interface in addition to microstructure and dendritic secondary arm spacing. Hot hardness at $500^{\circ}C$ showed higher than 300 HV.

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Improvement of Wear Resistance and Formation of Si Alloyed Layer on Aluminum Alloy by PTA Process (PTA법에 의한 Al 합금표면의 Si 합금층 형성과 내마모성 개선)

  • ;;松田福久;中田一博
    • Journal of Welding and Joining
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    • v.15 no.5
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    • pp.134-143
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    • 1997
  • The formation of thick alloyed layer with high Si content have been investigated on the surface of Al alloy (A5083) plate by PTA process with Si powder. Hardening characteristics and wear resistance of alloyed layer was examined in relation to the microstructure of alloyed layer. Thick hardened layer in mm-order thickness on the surface of A5083 plate can be formed by PTA process with wide range of process condition by using Si powder as alloying element because of eutectic reaction of Al-Si binary alloy. High temperature and rapid solidification rate of molten pool, which are features of PTA process, enable the formation of high Si content alloyed layer with uniform distribution of fine primary Si paticle. High plasma arc current was beneficial to make the alloyed layer with smooth surface appearance in wide range of powder feeding rate, because enough volume of molten pool was necessary make alloyed layer. Uniform dispersion of fine primary Si particle with about 30${\mu}{\textrm}{m}$ in particle size can be obtained in layer with Si content ranging from 30 to 50 mass %. Hardness of alloyed layer increased with increasing Si content, but increasing rate of hardness differed with macrostructure of alloyed layer. Wear resistance of alloyed layer depended on $V_{si}$(volume fraction of primary Si) and was remarkably improved to two times of base metal at 20-30% $V_{si}$ without cracking, but no more improvement was obtained at larger $V_{si}$.

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A Study on Formation of Thick Hardened Layer on Al Alloy Surface by PYAW Process (PTAW법에 의한 Al 합금 표면의 후막경화층 형성에 관한 연구)

  • 임병수;김봉수;오세훈;황선효;서창제
    • Journal of Welding and Joining
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    • v.15 no.5
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    • pp.92-103
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    • 1997
  • The purpose of this study is to improve the wear resistance and hardness of Al alloy by making a formation of the thick surface hardening layers. The thick surface hardening layers were formed by PTAW(Plasma Transferred Arc Welding), with the addition of metal powders (Cu), ceramics powders (NbC, TiC), and mixture powders (Cu+NbC) in Al alloy (A1050, A5083). Mechanical properties of overlaid layers (wear resistance, hardness) were investigated in relation to the microstructure. The results obtained are summarized as follows: The depth of penetration was increased with increasing powder feeding rate. It is considered that these increase were due to the thermal pinch effect by the addition of powders, especially, for the Cu powders, were due to the heat of reaction with the matrix. The hardness and wear resistance of overlaid layers were improved with increasing powder feeding rate. For the Cu powders, it is considered that these increase were due to the increase of the formation of ${\theta}(CuAl_2)$ phase with increasing feeding rate of Cu powers.

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Hardening Characteristics of Aluminum Alloy Surface by PTA Overlaying with Metal Powders (I) (플라즈마분체 오버레이법에 의한 알루미늄합금 표면의 경화특성에 관한 연구(I) -후막 표면 합금화층의 형성조건과 그 조직-)

  • ;中田一博;;;松田福久
    • Journal of Welding and Joining
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    • v.12 no.4
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    • pp.85-101
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    • 1994
  • Effect of Cr, Cu and Ni metal powders addition on the alloyed layer of aluminum alloy (AC2B) has been investigated with the plasma transferred arc (PTA) overlaying process. The overlaying conditions were 125-200A in plasma arc current, 150mm/min in process speed and 5-20g/min in powder feeding rate. Main results obtained are summarized as follows: 1) It was made clear that formation of thick surface alloyed layer on aluminum alloy is possible by PTA overlaying process. 2) The range of optimum alloying conditions were much wider in case of Cu and Ni powder additions than the case of Cr powder addition judging from the surface appearance and the bead macrostructure. 3) Alloyed layer with Cu showed almost the homogeneous microstructure through the whole layer by eutectic reaction. alloyed layers with Cr and Ni showed needle-like and agglomerated microstructures, the structure of which has compound layer in upper zone of bead by peritectic and eutectic-peritectic reactions, respectively. 4) Microconstituents of the alloyed layer were analyzed as A1+CrA $l_{7}$ eutectics, C $r_{2}$al sub 11/, CrA $l_{4}$, C $r_{4}$A $l_{9}$ and C $r_{5}$A $l_{*}$ 8/ for Cr addition, Al+CuA $l_{2}$(.theta.) eutectics and .theta. for Cu addition, and Al+NiA $l_{3}$ eutectics. NiA $l_{3}$, N $i_{2}$A $l_{3}$ and NiAl for Ni addition. 5) Concerning defect of the alloyed layer, many blow holes were seen in Cr and Ni additions although there was lesser in Cu addition. Residual gas contents in blow hole for Cu and Ni alloyed layer were confirmed as mainly $H_{2}$ and a littie of $N_{2}$ Cracking was observed in compound zone of the alloyed layer in case of Cr and Ni addition but not in Cu alloyed layer.r.r.

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