Plasma in the Thermal Spray Coating Industry

Abstract

Thermal plasma spraying (TPS) offered distinct advantages compared to alternate cold spray or combustion-based thermal spray technologies. Early applications of wire arc spraying were in the area of corrosion protection of marine large infrastructure such as bridges. The high temperatures and high velocities attained by DC spraying combined with the excellent control of the properties and the purity of the spray medium, especially with radiofrequency induction plasma spraying (RF-IPS), have further propelled the thermal plasma technology to a wider range of applications. Its downside, however, mostly in its complexity and high investment and operation cost, has limited its initial industrial-scale applications to the coating of high-end, high added-value parts in the aerospace and medical fields. With the further development of the technology and improvements in spray process automation, processing cost has steadily dropped, allowing the TPS technology to penetrate new areas such as the textile, paper, and chemical process industries, and, more recently, the automobile industry. In this chapter, following a brief review of the evolution of the thermal spray coating (TSC) industry on the international scale, a comparative analysis is made of the principal technologies, positioning the plasma-based technologies in comparison to alternate cold spray or combustion-based approaches. A survey of TSC applications by industrial sector is presented next, highlighting the areas in which TPS has been competitive and well-integrated on an industrial-scale production. The last part of this chapter is devoted to a technoeconomic analysis giving an order of magnitude of the investment cost associated with different thermal spray technologies and a comparative analysis of operating cost. Due to the dependence of the economic parameters on the regional infrastructure and local cost factors, emphasis is placed more on the methodology and the identification of the principal cost factors affecting the process economics rather than their absolute value that can change rapidly with time depending on the local economical context.