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 describes the two commonly used standardized tests for determining the mechanical properties of thermal spray coatings: hardness testing and tensile adhesion testing. It discusses the destructive and non-destructive methods of residual-stress measurement. Electrochemical testing methodologies include two distinctly different methods: direct and alternating current impedance techniques for assessing the corrosion resistance of coating attributes. The article also reviews the testing methods for determining thermomechanical and environmental stability of thermal barrier coatings. It discusses the wear testing methodologies that are standardized by ASTM, including the pin-on-disk, block-on-ring, dry sand/rubber wheel, erosion, metallographic apparatus abrasion, fretting wear, cavitation, reciprocating ball-on-flat, impact, and rolling contact fatigue test. The article concludes with a discussion on the methods of testing abradability and erosion resistance in abradable coatings.

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.

Agitation is one of the most critical areas of quench system design. This article provides an overview of the impact of agitation on quench uniformity, followed by a general discussion of the selection and use of various types of agitators, including recirculation pumps, jet mixers, forced air (sparging), and impellers. A brief overview of heat-exchanger types and their selection criteria is also provided, along with simplified calculations for approximating heat-exchange requirements. The methods of selecting a quenchant are provided. Recommendations for system maintenance are also described. Much effort is placed on the proper design of the furnace for temperature and atmosphere uniformity, proper temperature control, and exact carbon potential. However, the design of the quench tank can have a drastic effect on the overall system performance, with proper design ensuring proper mechanical properties (hardness, strength, and fracture toughness) as well as distortion control.

Sintering provides the interparticle bonding that generates the attractive forces needed to hold together the otherwise loose ceramic powder mass. It also improves hardness, strength, transparency, toughness, electrical conductivity, thermal expansion, magnetic saturation, corrosion resistance, and other properties. This article discusses the fundamentals of sintering and its effects on pore structures and particle density. It addresses some of the more common sintering methods, including solid-state, liquid-phase, and gas pressure sintering, and presents alternative processes such as reaction sintering and self-propagating, high-temperature synthesis. It also describes several pressure densification methods, including hot isostatic pressing, gas pressure sintering, molten particle deposition, and sol-gel processing. The article concludes with a section on grain growth that discusses the underlying mechanisms and kinetics and the relationship between grain growth and densification.

Laser-ultrasonics is a particular implementation of ultrasonic nondestructive inspection in which ultrasound is generated and detected by lasers. This article discusses the various mechanisms that ensure ultrasound generation and explains the possibility to get the equivalent of phase-array by numerical processing of an array of previously acquired laser-ultrasonic signals. The article describes the ultrasound generation by thermoelastic mechanism and ablation or vaporization. It illustrates the principle of optical detection of ultrasound with confocal Fabry-Perot interferometer and photorefractive two-wave mixing interferometer. The article concludes with information on the industrial applications of laser-ultrasonics, including thickness measurement, flaw detection, and material characterization.

This article is a detailed account of additive manufacturing (AM) processes for copper and copper alloys such as copper-chromium alloys, GRCop, oxide-dispersion-strengthened copper, copper-nickel alloys, copper-tin alloys, copper-zinc alloys, and copper-base shape memory alloys. The AM processes include binder jetting, ultrasonic additive manufacturing, directed-energy deposition, laser powder-bed fusion, and electron beam powder-bed fusion. The article presents a review of the literature and state of the art for copper alloy AM and features data on AM processes and industrial practices, copper alloys used, selected applications, material properties, and where applicable, compares these data and properties to traditionally processed materials. The data presented and the surrounding discussion focus on bulk metallurgical processing of copper components. The discussion covers the composition and performance criteria for copper alloys that have been reported for AM and discusses key differences in process-structure-property relationships compared to conventionally processed material. The article also provides information on feedstock considerations for copper powder handling.

This article discusses the fundamentals of thermal vaporization and condensation and provides information on the various vaporization sources and methods of vacuum deposition. It offers an overview of reactive evaporation and its deposition techniques. The article also explains the advantages, limitations, and applications of vacuum deposition processes. Finally, it provides information on the gas evaporation process, its processing chamber, and related systems.

This article is a compilation of definitions for terms related to engineering materials, including plastics, elastomers, polymer-matrix composites, adhesives and sealants, ceramics, ceramic-matrix composites, glasses, and carbon-carbon composites.

Ceramics usually require some form of machining prior to use to meet dimensional and surface quality standards. This article focuses on abrasive machining, particularly grinding, and addresses common methods and critical process factors. It covers cylindrical, centerless, and disk grinding and provides information on tooling, wheel selection, work material, and operational factors. It also discusses precision slicing and slotting, lapping, honing, and polishing as well as abrasive waterjet, electrical discharge, laser, and ultrasonic machining.