Thermal Spray Coatings

Abstract

The entire technology of thermal spraying is described starting from an overview of related industry and economic impact. The materials used in spraying including feedstock and substrate are shown and thermal spraying methods divided into (i) high productivity, (ii) high kinetic energy, (iii) controlled atmosphere, and (iv) nanostructured coatings are shortly described. Then the different aspects of coatings, in particular, composites, such as microstructure, and different properties are shown. A few examples of coating applications in different branches of industry are shown. Finally, the trends of the technology are detected and some aspects of security problems related to the technology are shown.

Use of Different Process Gases for Manufacturing Isolating Alumina Coatings by Flame Spraying with Cords

“…In addition to applications in wear or corrosion protection, thermally sprayed coatings or coating composites are increasingly used in the electronics industry, e.g., in conductor tracks or integrated circuits (Ref 1 , 2 ), due to their ability to adaptively adjust the final product properties (Ref 1 , 3 - 5 ). Another field of application that is currently under intensive investigation is the additive production of electrical devices in automotive engineering.…”

“…In particular, entire heaters for the vehicle interior are currently manufactured using a combination of different coating techniques due to a high degree of efficiency (Ref 6 ). An essential part for the proper function of such components is the ceramic isolating coating, which is mostly based on Al 2 O 3 (Ref 1 ).…”

“…Today, alumina coatings in the industry are mainly produced by atmospheric plasma spraying (APS) (Ref 1 , 7 - 9 ). However, it is common knowledge that thermally sprayed coatings of this material usually do not correspond to the same desired crystallographic modification as the bulk material.…”

“…However, it is common knowledge that thermally sprayed coatings of this material usually do not correspond to the same desired crystallographic modification as the bulk material. While sintered alumina thus mainly consists of the stable alpha phase, thermally sprayed coatings often experience process-induced transformations into several metastable phases like gamma, delta or theta (Ref 1 , 9 - 12 ). Being of hygroscopic nature (Ref 1 , 12 ), especially the metastable gamma phase has detrimental effects on the electrical resistivity of Al 2 O 3 coatings, which is crucial for the planned application.…”

Review of Functionally Graded Thermal Sprayed Coatings

“…2020, 10, x FOR PEER REVIEW 6 of 40 Figure 6. Phenomena occurring after injection of suspension droplet into plasma jet [14]. Roughness of coating's surface may vary in a very broad range (as reported in [35], Ra values may be between 1.6 and 14.1 µm); • Thickness may be as low as a few micrometers and reach hundreds of micrometers [38,39].…”