Atomization is the dominant method for producing metal and prealloyed powders from aluminum, brass, iron, low-alloy steels, stainless steels, tool steels, superalloys, titanium alloys, and other alloys. The general types of atomization processes encompass a number of industrial and research methods. This article describes the key process variables and production factors for the industrial methods: two-fluid, centrifugal, vacuum or soluble-gas, and ultrasonic atomization. It also reviews the effect of atomization methods and process variables on key powder characteristics such as the average particle size, particle size distribution or screen analysis, particle shape, chemical composition, and microstructure.

The process of transferring coating materials from the container to the surface to be coated can be accomplished in a number of ways. This article describes seven methods of coating application: brushes, rollers, and daubers; conventional air spray; high-volume low-pressure spray; airless spray; air-assisted airless spray; plural-component spray; and electrostatic spray. Factors to be considered when deciding on an application method include the size and configuration of the surfaces to be coated, the type of coating being applied, environmental regulations/restrictions, the proximity to other operations or personnel, and the recommendations of the coating manufacturer.

This article describes the various pure forms of carbon matrices and the corresponding methods used to create them or incorporate them into a matrix of a composite. These forms include graphite, diamond, fullerenes, and nanotubes. The article discusses the three types of liquid precursors, namely, thermoplastic, thermosetting, and evaporative or solvent carriers. It provides a description of the advantages and limitations of various methods involved in chemical vapor infiltration. The article concludes with a discussion on matrix contribution to composite properties.

This article describes the mechanism, advantages and disadvantages, fundamentals, capabilities, variations, equipment used, and weldability of metals in solid-state welding processes, including diffusion bonding, explosion welding, friction welding, ultrasonic welding, upset welding, and deformation welding.

This article discusses the production of aluminum and aluminum alloy powders with emphasis on the gas atomization method and the atomizing nozzle. It illustrates the particle formation mechanism and details the requisites for particle size distribution, control, and morphology. The article presents information on the mean oxide thickness formed on atomized powders. It also describes the mechanical and physical properties of aluminum and aluminum alloy powders, as well as their applications.

This article demonstrates the depth and breadth of commercial and third-party software packages available to simulate metals processes. It provides a representation of the spectrum of applications from simulation of atomic-level effects to manufacturing optimization. The article tabulates the software name, function or process applications, vendor or developer, and website information.

Computational fluid dynamics (CFD) is one of the tools available for understanding and predicting the performance of thermal-fluids systems. This article qualitatively describes the basic principles of CFD. The numerical methods, such as geometry description and discretization, used to solve the CFD equations are discussed. The article also demonstrates the application of CFD to a few casting problems.

This article focuses on lubricants classified as either internal combustion engine or nonengine lubricants, and the lubricant additives. The functional groups of chemically active and inert additives, as well as friction modifiers and other additives, are described in detail. The chemically active additives include dispersants, detergents, antiwear, and extreme-pressure agents, oxidation inhibitors, and rust and corrosion inhibitors. The chemically inert additives include emulsifiers, demulsifiers, pour-point depressants, foam inhibitors, and viscosity improvers. The article also discusses the multifunctional nature of additives and concludes with information on lubricant formulation.

This article focuses on those areas of coatings technology where silicon-based technology (SBT) is the primary enabling technology and where SBT is used as an additive to provide unique properties to the coating film. It describes the chemistry and the uses of alkoxy silanes. The uses of silicates, siliconates, silicone fluids, and silicone resins in coatings are reviewed. The article discusses the various applications of SBT, namely, primers, heat-resistant coatings, industrial maintenance coatings, hygienic coatings, and abrasion-resistant coatings, and for marine biofouling control. It also provides information on the benefits of silicon-base additives.

Joining is key to the manufacture of large or complex devices or assemblies; construction of large and complex structures; and repair of parts, assemblies, or structures in service. This article describes the three forces for joining: physical, chemical, and mechanical. It provides an overview of the joining processes, namely, mechanical fastening, integral attachment, adhesive bonding, welding, brazing, and soldering. The article concludes with information on the various aspects of joint design and location that determine the selection of a suitable joining method.

This article discusses coating products available for use in the aerospace industry that are compliant with regulations requiring reductions in emissions from organic solvents. The coating products addressed include primers, topcoats, and chemical milling maskants. It describes their characteristics and limitations compared to conventional noncompliant materials. The article addresses the methods and products commonly used achieve regulatory compliance: waterborne coatings, exempt-solvent-based coatings, high-solids coatings, powder coating, and electro-deposition.

The technology to fabricate lower-density, porous powdered metal materials provides unique engineering solutions for many applications. This article summarizes the characteristics and applications of porous powder metallurgy technology, as well as the fabrication methods employed.

Tribology is the science and technology of interacting surfaces in relative motion. This article describes in detail the basic structural, operational, and interaction parameters of a tribosystem. The interaction parameters, which characterize the action of the operational parameters on the structural components in the system, consist of three important aspects: contact parameters, friction parameters, and wear parameters. These three aspects embody the complex mechanisms and relationships between the constituents of a tribosystem. The article concludes with information on the selection criteria of a material for wear applications.

This article focuses on different aspects of wear particle analysis. It discusses the different wear regimes in the wear rate versus time (bathtub) curve. The article explains the essence of condition monitoring and how to properly sample lubricants for condition monitoring. It also discusses in-service lubricant analysis for condition monitoring, focusing on the spectrometric oil analysis program. The article describes the characteristics of wear particles and analytical techniques for characterizing them. It also describes the characteristics of different types of wear particles and the mechanisms by which they are generated. The article concludes with a summary of the major applications of wear particle analysis.

This article provides a comprehensive review and critical assessment of numerical modeling of heat and mass transfer in fusion welding. The different fusion welding processes are gas tungsten arc welding, gas metal arc welding, laser welding, electron beam welding, and laser-arc hybrid welding. The article presents the mathematical equations of mass, momentum, energy, and species conservation. It reviews the applications of heat transfer and fluid flow models for different welding processes. Finally, the article discusses the approaches to improve reliability of, and reduce uncertainty in, numerical models.

This article discusses the functions of lubricants to prevent premature failure of rolling element bearings and the advantages of fluid lubrication. It describes the composition of refined mineral oil for rolling bearing applications. The article reviews the types and properties of nonpetroleum oils, such as polyglycols, phosphate esters, silicone fluids, dibasic acid esters, and fluorinated polyethers. It discusses the properties of greases, including grease speed limits, grease composition, relubrication intervals, corrosion prevention behavior, and grease compatibility. The article concludes with a discussion on polymeric lubricants and solid lubricants.

This article provides a brief introduction to lubrication as a method to reduce friction between two surfaces. It discusses the surface characteristics of parts and explores how lubrication helps separate two contacting surfaces and thereby decreases the coefficient of friction. The article details the classifications of lubrication regimes, namely, boundary, mixed, hydrodynamic, and elastohydrodynamic lubrications. It discusses the various types of lubricant materials and additives, including liquid lubricants, solid lubricants, gaseous lubricants, greases, green lubricants, and nanomaterials. The article also reviews the properties of lubricants. It describes the tribological evaluation of lubricants, including stribeck test, four-ball test, block-on-ring test, pin-in-vee test, and reciprocating motion test.

Microjoining with high energy density beams is a new subject in the sense that the progress of miniaturization in industry has made the desire to make microjoints rapidly and reliably a current and exciting topic. This article summarizes the current state of microjoining with both electron and laser beams. It considers the elementary physical processes such as heat and fluid flow to introduce the reader to the phenomena that affect melting, coalescence, and solidification needed for a successful microweld. The various forces driving (and resisting) fluid flow are analyzed. The article discusses the equipment suitable for microjoining and the metallurgical consequences and postweld metrology of the process. It also provides examples of developmental welds employing laser and electron beam microwelding techniques.

Milling of materials, whether hard and brittle or soft and ductile, is of prime interest and of economic importance to the powder metallurgy (PM) industry. This article discusses the principles of milling, milling parameters, and the powder characteristics required for the process. It discusses the changes in powder particle morphology that occur during milling of metal powders produced by various processes such as microforging, fracturing, agglomeration, and deagglomeration. The article also provides useful information on milling equipment such as tumbler ball mills, vibratory ball mills, attrition mills, and hammer and rod mills.