This article discusses the process details of metal powder injection molding of microcomponents and the powder particle characteristics of feedstock and property requirements of binders. It reviews important characteristics to be considered in the processing steps: venting, channel diameters, binder segregation, binder degradation, feedstock supply, temperature control, demolding, debinding, and sintering. Finally, the article provides information on powder injection molding mold-filling simulation and two-component powder injection molding, offering a method for high-volume production of microcomponents made of multifunctional materials.

Various powder production processes allow precise control of the chemical composition and physical characteristics of powders and allow tailoring of specific attributes for targeted applications. Metal powders are produced by either mechanical methods or chemical methods. The commonly used mechanical methods include water and gas atomization, milling, mechanical alloying, and electrolysis. Some chemical methods include reduction of oxides. This article provides information on the reliable techniques for powder characterization and testing to evaluate the chemical and physical properties of metal powders, both as individual particles and in bulk forms.

Tungsten, molybdenum, and cemented carbide parts can be produced using several additive manufacturing technologies. This article classifies the most relevant technologies into two groups based on the raw materials used: powder-bed methods, such as selective laser melting, electron beam melting, and binder jet three-dimensional (3-D) printing, and feedstock methods, such as fused-filament fabrication and thermoplastic 3-D printing. It discusses the characteristics, processing steps, properties, advantages, limitations, and applications of these technologies.

This article briefly reviews the production methods and characteristics of plain carbon and low-alloy water-atomized iron and steel powders, high-porosity iron powder, carbonyl iron powder, and electrolytic iron powder. It emphasizes on atomized powders, because they are the most widely used materials for ferrous powder metallurgy. The article provides information on the properties and applications of these powders. It also includes an overview of diffusion alloying, basics of admixing, and bonded premixes.

This article describes the methods for determining the flow rate of metal powders. It examines the factors affecting flow rate, apparent density, and angle of repose of metal powders. The article reviews the frictional properties, cohesive strength, frictional properties, tap density, and compressibility of metal powders. It explains the mechanisms of powder segregation. The article provides information on green strength and springback value of rectangular test bar. It concludes with a discussion on the chemical composition of metal powders.

Very high density materials are used for such applications as counterweights and radiation shields. This article focuses on the metallurgy, processing, properties, fabrication, design considerations, health and safety considerations, and applications of the most commonly used very high density materials: depleted uranium and tungsten and their alloys.

Horizontal centrifugal casting is used to cast parts having an axis of revolution. This article discusses the operations of three types of horizontal casting machine: the flanged shaft machine, the horizontal roller-type machine, and the double-face plate machine. It provides information on expendable and permanent molds used for centrifugal casting. The parameters and operations of the horizontal centrifugal casting process, including pouring and solidification, as well as the applications are described.

No-bake sand molds are based on the curing of inorganic or organic binders with either gaseous catalysts or liquid catalysts. This article reviews the major aspects of no-bake sand bonding in terms of coremaking, molding methods, and sand processing. It discusses the points to be noted in handling sand-resin mixtures for no-bake molds or cones and lists some advantages of no-bake air-set cores and molds. The article describes the process procedures, advantages, and disadvantages of gas curing and air-setting hardening of sodium silicates. It examines the members of the air-setting organic binders, namely, furan no-bake resins, phenolic no-bake resins, and urethanes. The article provides an overview of gas-cured organic binders. It also illustrates the three commercial systems for sand reclamation: wet reclamation systems, dry reclamation systems, and thermal reclamation.

Fluxes are added to the welding environment to improve arc stability, to provide a slag, to add alloying elements, and to refine the weld pool. This article describes the effect of oxygen that directly reacts with alloying elements to alter their effective role by reducing hardenability, promoting porosity, and producing inclusions. It proposes basicity index for welding as a measure of expected weld metal cleanliness and mechanical properties. The article discusses alloy modification in terms of slipping and binding agents, slag formation, and slag detachability. It reviews the types of fluxes for different arc welding processes, such as shielded metal arc welding (SMAW), flux-cored arc welding (FCAW), and submerged arc welding (SAW).

The residual porosity in sintered refractory metal ingots is usually eliminated by different densification processes, such as thermomechanical processes. This article focuses on thermomechanical processing of tungsten, molybdenum, and tantalum. It provides an overview of liquid-phase sintering of tungsten heavy alloys and describes the infiltration of tungsten and molybdenum for attaining full density. The article concludes by providing information on hot isostatic pressing of refractory metal alloys to full density.

This article focuses on the significant fundamental powder characteristics, which include particle size, particle size distribution, particle shape, and powder purity, followed by an overview of general and individual powder production processes such as mechanical, chemical, electrochemical, atomizing, oxide reduction, and thermal decomposition processes. It also covers the consolidation of powders by pressing and sintering, as well as by high density methods. Further emphasis is provided on the distinguishing features of powders, their manufacturing processes, compacting processes, and consolidated part properties. In addition, a glossary of powder metallurgy terms is included.

This article focuses on various vacuum heat treating processes for additively manufactured parts, namely annealing and stress relieving, solid-solution annealing, and solution treating and aging. It addresses several practical concerns involved in using vacuum heat treatment, including temperature measurement, unvented cavities, loose powder, and direct contact of metals in the high-temperature vacuum. The article provides a short discussion on sintering and evaporation of metals in vacuum furnaces.

This article describes two rapid tooling technologies, namely, direct rapid tooling and indirect rapid tooling, for forging-die applications. Commonly used direct rapid tooling technologies include selective laser sintering, three-dimensional printing, and laser-engineered net shape process. The indirect rapid tooling technologies include 3D Keltool process, hot isostatic pressing, rapid solidification process tooling, precision spray forming, and radially constricted consolidation process.

This article explains how ceramic powders are made. It begins by briefly describing the raw materials used in structural clay products, whitewares, refractories, and advanced ceramics. It then examines various additives that promote uniformity at different stages of the process. After a description of the comminution process (wet and dry milling methods), it discusses batching and mixing operations and granulation methods. The article also deals with the effect of process variables and the steps involved in chemical synthesis, including preparation from solution and gas-phase reactions, filtration and washing, and powder recovery techniques. It concludes with a discussion on characterization, centering on size distribution analysis, specific surface area, density, porosity chemical composition, phase, and surface composition.

Blending of powders is defined as the thorough intermingling of powders of the same nominal composition. Premixing is the preparation of a uniform mixture of two or more components. This article provides information on the blending and premixing variables required to produce adequate results in the powder mixture. It describes the effects of metal powder characteristics on blending and mixing: particle size, shape, density, and surface features. The article also provides information on the equipment, tumble-type blenders, and low-shear agitated-type blenders used for blending and premixing solids.

Ceramic-forming processes usually start with a powder which is then compacted into a porous shape, achieving maximum particle packing density with a high degree of uniformity. This article compares and contrasts several forming processes, including mechanical consolidation, dry pressing, cold isostatic pressing, slip casting, tape casting, roll compaction, extrusion, and injection molding. It describes the advantages, equipment and tooling, and material requirements of green machining, the machining of ceramics in an unfired state with the intent of producing parts as close to as possible to their final shape. The article also provides useful information on drying methods, shrinkage, and defects as well as the removal of organic processing aids such as dispersants, binders, plasticizers, and lubricants.

This article contains tables that list standard reduction potentials for electrochemical reactions. The first table lists reactions alphabetically by element of interest. The second table is ranked by potential value. Potential is measured versus the Standard Hydrogen Electrode which has a value of 0.0000 V. Reactions with more than one voltage indicate that results have not been reconciled. Parenthetical materials not needed to balance reactions are catalysts.

Traditional processing methods for the part production of Co-Cr alloys include casting, powder metallurgy, and metal forming. However, the steps involved during materials processing followed by metal forming and machining are time consuming and fraught with processing variables. Three-dimensional (3D) printing enables rapid evolution in design, personalization, and so on. This article presents a brief description of some common additive manufacturing (AM) processes for the production of cobalt alloy parts, and provides a comparison between AM and conventional processing methods. The discussion is centered on process-microstructure-properties correlation in additively manufactured cobalt alloys and applications of these alloys.

Fluxes are added to the welding environment to improve arc stability, provide a slag, add alloying elements, and refine the weld pool. This article discusses the effect of oxygen, which is an important chemical reagent to control the weld metal composition, microstructure, and properties. It provides information on the inclusions that form as a result of reactions between metallic alloy elements and nonmetallic tramp elements, or by mechanical entrapment of nonmetallic slag or refractory particles. The article reviews the considerations of flux formulation during shielded metal arc welding and flux cored arc welding (FCAW). It describes the types of fluxes used for submerged arc welding and FCAW as well as five essential groups of flux ingredients and their interactions.

This article provides a brief overview of additive manufacturing (AM) of tool steels via various AM technologies such as laser powder bed fusion, electron powder bed fusion, blown powder directed energy deposition, and binder jet AM. The discussion includes process overview and covers the mechanism, advantages, and applications of each of these techniques.