In most small and medium enterprises (SMEs) that conduct plasma spraying, a one-cathode, one-anode plasma generator (OCOAPG) is used due to its cost-effectiveness. To achieve high deposition rates, the highest possible fraction of the injected powder has to be melted and accelerated toward the substrate. A sufficiently long and reproducible residence time in plasma is needed that is adequate in relation to the amount and size of the particles This can be achieved by a long plasma jet with little or no temporal variation in length and temperature. In OCOAPG, an arc is operated between a cathode and a central tubular anode, which causes different instabilities in the effluent plasma jet. Due to the instable interaction between the plasma jet and the carrier gas jet continuously incorporating the powder, fluctuations occur resulting in reduced coating quality. Coating systems with a higher number of electrodes (and hence using several arcs) show higher stability and therefore can provide higher coating quality. However, due to their complexity and cost intensity, the investment hurdle for SMEs usually turns out to be too high. Recently, research steps to improve the plasma spraying process with OCOAPG have been undertaken by using a controllable current source to create a uniform interaction between the particle and the gas jet. As the movement of the anodic arc attachment can be actively controlled by current pulses, the plasma jet can be lengthened and shortened at periodic intervals. Furthermore, by pulsing the particle delivery synchronously to the power modulation, an improved particle penetration and consistent residence times can be achieved. First diagnostic results, including example coatings, are presented and discussed within the paper.

Due to the growing application fields, the development of plasma generators has become increasingly important in recent years. Nowadays, DC-plasmas used for a plethora of coatings on metallic surfaces, metallization of plastic materials, surface cleaning and activation, plasma welding and spacecraft propulsion systems. The use of plasma generators for surface coating has grown enormously in the field of thermal insulation and wear-resistant coatings, especially with regard to deposition of refractory oxide ceramic layers using powders such as aluminum oxide, alumina / titania, zirconia and chromium oxide. In addition, for the plasma-assisted surface treatment, generators for both wide extended planar surfaces, as well as structures that are more complex have designed and industrially established. Nonetheless, new plasma sources still developed to provide more-efficient, tailor-made solutions due to their specific characteristics. Within this paper, a brief overview of the new innovative development of DC-plasma generator “Penta” shown. Thereby the special setup, first diagnostic results, including coatings, presented and discussed. The paper concludes with an outlook for future diagnostic measurements and possible future applications for this DC-plasma torch.

The use of plasma generators for thermal surface coating has grown enormously in the field of thermal insulation and wear-resistant coatings, especially with regard to deposition of refractory oxide ceramic layers using powders such as aluminum oxide, alumina / titania, zirconia and chromium oxide. Nonetheless, innovative plasma sources are still being developed to provide more-efficient, tailor-made solutions due to their specific characteristics. A brief overview of the DC-plasma generator Mettech “Axial III” are shown, which generator are allowed to use the central injection (advantage for suspension applications). In this paper first diagnostic results characterized the physical behaviour and special plasma symmetry, which can be described by three partial plasma jets. Thereby computer tomography (CT), high speed camera investigations coupled with time-adjusted current-voltage measurements, particle parameter detections and first resulting coatings are presented and discussed. The complete paper concludes with an outlook for future diagnostic measurements and possible future applications for this DC-plasma torch.

This paper discusses a research project with the goal of homogenizing the properties of three-cathode plasma sprayed coatings through the use of advanced diagnostics and numerical simulations. The approach included the development of a suspension injection setup, the determination of plasma and suspension behavior through diagnostic methods such as computer tomography and particle image velocimetry, and the analysis of coating formation through computational fluid dynamics and finite element analysis. The results of their investigations are presented, including tomographic reconstructions of temperature distribution, suspension behavior measurements, and coating analysis. The paper concludes with a discussion of the future directions of their research and the potential impact on the field of thermal spray coatings.