The Influence of Anode Inner Contour on Atmospheric DC Plasma Spraying Process

• Main Authors: Kui Wen, Min Liu, Kesong Zhou, Xuezhang Liu, Renzhong Huang, Jie Mao, Kun Yang, Xiaofeng Zhang, Chunming Deng, Changguang Deng
• Format: Article
• Language: English
• Published: Hindawi Limited 2017-01-01
• Series: Advances in Materials Science and Engineering
• Online Access: http://dx.doi.org/10.1155/2017/2084363

In thermal plasma spraying process, anode nozzle is one of the most important components of plasma torch. Its inner contour controls the characteristics of plasma arc/jet, determining the motion and heating behaviors of the in-flight particles and hence influencing the coating quality. In this study, the effects of anode inner contour, standard cylindrical nozzle, and cone-shaped Laval nozzle with conical shape diverging exit (CSL nozzle) on the arc voltage, net power, thermal efficiency, plasma jet characteristics, in-flight particle behaviors, and coating properties have been systematically investigated under atmospheric plasma spraying conditions. The results show that the cylindrical nozzle has a higher arc voltage, net power, and thermal efficiency, as well as the higher plasma temperature and velocity at the torch exit, while the CSL nozzle has a higher measured temperature of plasma jet. The variation trends of the plasma jet characteristics for the two nozzles are comparable under various spraying parameters. The in-flight particle with smaller velocity of CSL nozzle has a higher measured temperature and melting fraction. As a result, the coating density and adhesive strength of CSL nozzle are lower than those of cylindrical nozzle, but the deposition efficiency is greatly improved.