Thermal spray processes involve complete or partial melting of a feedstock material in a high-temperature flame, and propelling and depositing the material as a coating on a substrate. This article describes the properties of sprayed electronic materials, including dielectrics, conductors, and resistors, and discusses their implications and associated limitations for device applications and potential remedial measures. The article presents specific examples of electrical/electronic device applications, including electromagnetic interference/radio-frequency interference shielding, planar microwave devices, waveguide devices, sensing devices, solid oxide fuel cells, heating elements, electrodes for capacitors and other electrochemical devices.

This article presents the major thermal spray processes and their subsets, presenting each of the commercially significant processes together with some of their important variations. Each process is presented along with the attributes that influence coating structure and performance. The article summarizes the essential equipment components and necessary controls. The various thermal spray processes are conventional flame spray, detonation gun, high-velocity oxyfuel spray, electric arc spray, and plasma arc spray. Other processes, such as cold spray, underwater plasma arc spray, and extended-arc and other high-energy plasma arc spray, are also considered.

This article is a compilation of definition of the terms related to thermal spray coating technology.

The distinguishing feature of the cold spray process, when compared with the conventional thermal spray process, is its ability to produce coatings with high-velocity rather than high-temperature particle jet. This article provides an overview of the cold spray process and the parameters that affect both the process deposition efficiency and properties of the prepared coatings. It describes a variety of cold spray coating materials, namely, pure metals, ferrous and nonferrous metal alloys, composites, and cermets. The article presents various industrial applications of cold spray coatings.

Significant expansion of thermal spray technology occurred with the invention of plasma spray, detonation gun, and high-velocity oxyfuel (HVOF) deposition technologies. This article provides a brief history of the major initiating inventions/developments of thermal spray processes. It provides information on feedstock materials developed for specific thermal spray processes.

This article introduces thermal spray coatings and describes the various types of coating processes and coating devices, including the flame spray, electric-arc spray, plasma spray, transferred plasma arc, high-velocity oxyfuel, and detonation gun. It provides information on the surface preparation methods and finishing treatments of coated parts. The article also explains the tests to evaluate the coating quality and the effects of coating structures and mechanical properties on coated parts. It concludes with a discussion on the uses of thermal spray coatings.

Nuclear power plants benefit from thermal spray coatings for corrosion and erosion minimization and dimensional restoration of worn parts. This article provides a detailed discussion on the advantages of thermal spray coatings, fission reactor component coatings, and coatings for nuclear fuel processing before and after irradiation for power plant applications. Nuclear fusion research is divided into two primary fields of study categorized by the method for confining the fusion fuel: magnetic confinement fusion and inertial confinement fusion.

This article discusses the safety issues associated with the design and operation of thermal spray booths and spray box structures and the equipment or systems required for operating thermal spray processes. It describes the design elements necessary to mitigate sound, dust and fume, ultraviolet light, and mechanical hazards. The means selected for safeguarding personnel must be based on a formal risk assessment that meets ANSI/RIA standards. The safeguards include sensing devices, barriers, awareness signals, procedures, and training. It also provides guidelines that are intended to increase the safety awareness and the use of safety practices for gas and liquid piping and electrical equipment within thermal spray installations.

This article discusses various control processes carried out in powder feeding, thermal spraying, and gas flow of the thermal spray process to standardize the coating quality. Quality of the entire powder feeding process can be achieved by controlling the processing of feeding equipment as well as the characteristics of the powder being fed. Gas flow control can be achieved by using rotameters, critical orifices, and thermal mass flowmeters, whose ability to provide useful information is defined by their resolution, accuracy, linearity, and repeatability. The commercial thermal spray controls discussed here include the open-loop input-based, open-loop output-based, closed-loop input-based, and closed-loop output-based or adaptive controls. The article discusses the common causes and practical solutions for arc starting problems. It also outlines certain important developments in measuring individual and collective particle velocities, temperature, and trajectories as well as other plume characteristics for the plasma spray process.

This article discusses three types of powder-feeder systems that are commonly used throughout the thermal spray (TS) industry: gravity-based devices, rotating wheel devices, and fluidized-bed systems. It provides information on the various mechanical methods for producing powders, namely, crushing, milling, attriting, and machining. The article describes two prime methods of agglomeration. One method uses a binder by way of agglutination, while the other relies on a sintering operation. The article discusses the technology and principles of the processes that relate to thermal spraying, and offers an understanding for choosing particular feedstock materials that are classified based on the thermal spray process, material morphology, chemical nature of the material, and applications. Sieving, the most common method of separating powders into their size fractions, is also reviewed. The article also provides information on the topical areas and precautions to be undertaken to protect the operator from safety hazards.

The hazards associated with thermal spray deposition processes include ultraviolet and infrared radiation; acoustical noise; and by-product production in the forms of nitrous oxides, ozone, fumes, and dust. The most important consideration in health and safety is to use the engineered controls of hazards. This article provides a brief description of the spray booth, the most commonly used engineering tool to separate the operator from the thermal spray process and confine the associated hazards. It also presents guidelines on the proper and safe handling of industrial gases and ventilation and heat exhaust. The article provides information on the personal protective equipment for eyes and skin from radiation, and ears from noise. It also discusses other potential safety hazards associated with thermal spraying, namely, magnetic fields and infrasound.

Thermal spray is a generic term for a group of coating processes used to apply metallic, ceramic, cermet, and some polymeric coatings for a broad range of applications. This article provides a brief description of commercially important thermal spray processes, namely, powder-fed flame spray, wire- or rod-fed flame spray, electric arc spray, plasma arc spray, vacuum plasma spray, high-velocity oxyfuel spray, detonation gun deposition, and cold spray, and their advantages. It provides details on the microstructural characteristics of thermal spray coatings. The article also presents information on a wide variety of materials that can be thermal sprayed, such as metals, ceramics, intermetallics, composites, cermets, polymers, and functionally gradient materials. Tables are included, which list the thermal spray processes and coating properties of importance for various industrial applications.

The use of renewable energy has grown strongly in all end-use sectors such as power, heat, and transport. This article describes thermal spray applications that improve efficiency, lower maintenance costs, and prolong operational life in the renewable energy technologies, including wind power, hydro power, biomass and biofuels, solar energy, and fuel cells.

Thermal inspection comprises all methods in which heat-sensing devices or substances are used to detect irregular temperatures. Inspection of workpieces can be used to detect flaws and undesirable distribution of heat during service. Though there are several methods of thermal inspection and many types of temperature-measuring devices and substances, this article focuses only on thermography, which is the mapping of isotherms, or contours of equal temperature, over a test surface, and on thermometry, which is the measurement of temperature. Thermography techniques can be classified as contact thermographic methods using cholesteric liquid crystals, thermally quenched phosphors, and heat-sensitive paints, and noncontact techniques using hand-held infrared scanners, high-resolution infrared imaging systems, and thermal wave interferometer systems. Contact thermometric inspection devices include bolometers, thermocouples, thermopiles, and meltable substances, whereas radiometers and pyrometers come under the noncontact category.

Metallography plays a significant role in the quality control of metals and alloys used in the manufacture of implantable surgical devices. This article provides information and data on metallographic techniques along with images showing the microstructure of biomedical orthopedic alloys, including stainless steels, cobalt-base alloys, titanium and titanium alloys, porous coatings, and emerging materials.

Thermal spray coatings are often modified or treated by a variety of post-coating operations to transform the as-coated material into a final product based on coating composition and application. This article provides a detailed description of the post-coating operations that fall under two basic categories: surface treatments, such as dimensional, non-dimensional, and geometric finishing; and internal treatments, such as sealing, heat treating, and peening. It also describes various inspection and testing methods, including destructive and non-destructive inspections, often employed after post-coating operations.

This article provides information on metals that can be cast in permanent molds. It describes the advantages, disadvantages, applications, and design of permanent castings. Following a discussion on the factors considered in mold design and material selection, the article details the application of mold coatings and examines the effects of major processing variables on mold life. The variables that determine mold temperature and measures for controlling it are reviewed, and the effects of short-term and long-term variables on the dimensional accuracy of permanent mold castings are explained. The article concludes with a discussion on the factors influencing the surface finish on permanent mold castings.