• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1736-1741
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• 2003

The characteristics plasma flow of an atmospheric plasma torch used for thermal plasma processing is studied. In general, it is produced by the arc-gas interactions between a cathode tip and an anode nozzle. The performance of non-transferred plasma torch is significantly dependent on jet flow characteristics out of the nozzle. In this work, the distribution of gas flow that goes out to the atmosphere through a plenum chamber and nozzle is analyzed to evaluate the performance of atmospheric plasma torch. Numerical analysis is carried out with various angles of an inlet flow which can create different swirl flow fields. Moreover, the size of plasma plume is experimentally depicted.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.9
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• pp.138-145
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• 1999

Surface hardening of AC4C aluminium alloy with TiC powders was obtained by plasma transferred are (PTA) method, Bead appearance, microstrucutre and wear behavior were characterized in relation to the torch current, powder feed rate and wear condition. The width and the depth of bead were mainly increased with increasing torch current. The comparison of wear behavior between AC4C alloy and PTA treated AC4C alloy showed the remarkable enhancement of wear resistance.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1660-1662
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• 1997

High temperature arc plasma technologies are recently being developed in Europe, Japan and United States as one or the treatment schemes of municipal wastes, industrial wastes and vitrification of low level radioactive wastes. An experimental plasma melting furnace, a transferred type plasma torch and 100kW class power supply have been made. Operation of this system and some basic experimental results for solid wastes treatment are reported.

• 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.

• 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.

• 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.

• Journal of the Korean institute of surface engineering
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• v.35 no.4
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• pp.241-248
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• 2002

Hardfacing layers of Stellite 6 alloy with different molybdenum content are deposited on AISI 1045 carbon steel using plasma transferred arc welding (PTAW). The properties of the hardfacing layer are investigated in order to clarify the effect of molybdenum addition to the cobalt-base alloy. With an increase in molybdenum contents, the size of Cr-rich carbides in the interdendritic region is abruptly refined, but volume fraction of the carbide slightly increases. Also, with an increase of Mo, $M_{6}$ C type carbides are formed instead of Cr-rich $M_{7}$ $C_{3}$ type carbided, and this microstructural change enhanced the mechanical properties of Stellite 6 alloy.

• Proceedings of the KAIS Fall Conference
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• 2004.06a
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• pp.92-95
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• 2004

플라즈마 트랜스퍼드 아크(PTA) 용사는 플라즈마 아크 용접 장치에 선형의 용접봉을 이용하는 대신 분말 형태의 용접재를 주입하여 주로 마모나 부식에 노출되는 금속의 표면에 적용하여 금속 표면의 내식 내마모 특성을 향상시키는 기술이다. 본 논문에서는 용사전류가 표면개질부에 미치는 기하학적 형상 및 미세조직에 미치는 영향에 대하여 알아보았다. 낮은 전류에서는 접합이 이루어지지 않았고 높은 전류에서는 모재로 희석되어 들어가는 현상을 보였다.

• 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.

• 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 $V_{si}$.