Characteristics and Thermal Efficiency of a Non-transferred DC Plasma Spraying Torch Under Low Pressure

Abstract

Current-voltage (I-V ) characteristics of a non-transferred DC arc plasma spray torch operated in argon at vacuum are reported. The arc voltage is of negative characteristics for a current below 200 A, flat for a current between 200 A to 250 A and positive for a current beyond 250 A. The voltage increases slowly with the increase in carrier gas of arc. The rate of change in voltage with currents is about 3∼4 V/100 A at a gas flow rate of about 1∼1.5 V/10 standard liter per minute (slpm). The I-V characteristics of the DC plasma torch are of a shape of hyperbola. Arc power increases with the argon flow rate, and the thermal efficiency of the torch acts in a similar way. The thermal efficiency of the non-transferred DC plasmatron is about 65∼78%.

Characteristics and Temperature Measurement of a Non-Transferred Cascaded DC Plasma Torch

“…Typically, for a current below 150 A the V -I characteristic shows a negative slope, which then turns positive beyond a plasma current of 200 A, a trend also noticed in previous studies [16] . The corresponding range of the plasma current as reported by BAO Shicong et al [16] is slightly higher than our results. They got a negative slope below a current of 200 A and a positive slope above 250 A.…”

“…The measured efficiency of the plasma torch is found to be in the range from 36% to 48%, for different gas flow rates and currents, which always increases with the gas flow rate and arc power, for a constant current. However, the efficiency reported for thermal plasma spraying torches [14,16] is higher than our measured values. BAO Shicong et al [16] reported on achieving an efficiency in the range of 65% and 78%, with an almost similar trend.…”

“…6. The plasma power increases with the increase in the gas flow rate, which was also reported by BAO Shicong et al [16] . For a higher current, the variation in plasma power is higher, whereas the variation in power at a low current is smaller.…”

“…have been investigated by various authors [8∼15] . Very recently, BAO Shicong et al [16] reported the V -I characteristics of a non-transferred DC thermal plasma spraying torch, including its thermal efficiency, for different powers and gas flow rates. Perhaps due to the complicated nature of the experiment, the structure of the potential inside the torch has not been investigated yet.…”

Effect of Spraying Parameters on the Microstructure and Mechanical Properties of Micro-Plasma Sprayed Alumina-Titania Coatings

“…It is known that the plasma power increases with the increase in gas flow rate [15,19,20] . Also, the particle velocity increases with the gas flow rate.…”