This article focuses on the fractography features of the conventional powdered metal (PM) process for ferrous powders. It discusses porosity, which is one of the inherent features present in components produced by conventional press-and-sinter processes, and green cracks, which are the most common fracture issue in conventional PM processes. It explains the effect of post-sintering operations. The article also presents the common ferrous powder metallurgy materials.

This article describes some of the underlying factors of tool steel and bearing steel fractures and appearances. It also briefly introduces the general types of cold work and hot work tool steels and their typical performance requirements. This includes the importance of microstructural conditions achieved with powder metallurgy (PM) tool steels and the need for steel “cleanliness,” especially in preventing contact fatigue in bearings or bending fatigue in gears.

This article provides an overview of the supply chain for metallic additively manufactured materials, with an emphasis on spherical alloy powders. The article describes powder production processes as well as the various metal alloys that can be produced using powder AM techniques. It also reviews the basic characteristics of powder feedstocks and the management of metallic powders.

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 provides an overview of the general methods of metal powder production. It details the primary methods for particle sizing used in additive manufacturing: sieving, laser diffraction and scattering, and digital image analysis. Methods of interpreting and understanding particle size distribution (PSD) data are presented, with an emphasis on the differences between count- and volume-based PSDs. The article then outlines practices for both qualitative and quantitative assessment of particle morphology.

This article focuses on binder-jetting technologies in additive manufacturing (AM) that produce metal artifacts either directly or indirectly. The intent is to focus on the most strategic and widespread uses of the binder jetting technology and review some of the challenges and opportunities for that technology. The discussion includes a historical overview and covers the major steps involved and the advantages of using the binder jetting process. The major steps of the process covered include printing, curing, de-powdering, and sintering.

This article presents a detailed account of the processes involved in vat-photopolymerization-based fabrication of ceramics, namely bioceramics, structural ceramics, piezoelectric ceramics, optical ceramics, and polymer-derived ceramics. Information and methods of material preparation, curing characteristics, green-part fabrication, property identification, process design and planning, and quality control and optimization are introduced. The article also provides information on postprocessing techniques, namely debinding and sintering, as well as on the phenomenon of shrinkage and compensation.

In general, metal-matrix composites (MMCs) are classified into three broad categories: continuous fiber-reinforced composites, discontinuous or short fiber-reinforced composites, and particle-reinforced composites. This article focuses on stir casting and melt infiltration as the two main methods of MMC solidification processing. It describes the MCC casting methods, such as sand and permanent mold casting, centrifugal casting, compocasting, and high-pressure die casting. The article discusses the MMC infiltration processes in terms of pressure infiltration casting and liquid metal infiltration. It reviews the powder metallurgy processing of aluminum MMCs and deformation processing of discontinuously reinforced aluminum composites. The article concludes with a discussion on the processing of fiber-reinforced aluminum.

This article describes manufacturing procedures that produce aluminum foams and have since become industrially important and successful. It discusses the foaming of melts by blowing agents and foaming of melts by gas injection. The article focuses on aluminum foams based on the Foaminal technology, because those foams dominate the technical applications of aluminum foams. It also discusses the mechanical properties of metal foams, such as general compression behavior, elastic behavior, strain-rate sensitivity, tensile behavior, ductility, fatigue, and mechanical damping. The article concludes with information on the applications of highly porous metal structures.

Aluminum powders can be formed into components by several competing technologies, including powder metallurgy (PM), metal injection molding, powder forging, and additive manufacturing. This article explores PM methodologies that are being exploited to manufacture such components. It reviews emerging technologies that promise to offer exciting ways to produce aluminum parts. The article discusses the various steps involved in PM, such as powder production, compaction, sintering, repressing, and heat treatment. It provides information on aluminum production statistics and the wear-resistance applications of PM.

This article provides a broad overview of sliding and adhesive wear, its processes, and its control, with special attention to three general classes of materials: metals, ceramics, and polymers. It discusses the ways in which materials can be damaged and removed during sliding contact. The article explains the physical and chemical nature of sliding surfaces. It presents wear equations, design criteria, and criteria for selection of materials. The article also describes the factors that affect wear performance of hybrid sliding systems. It concludes by providing general guidelines to prevent the sliding and adhesive wear in metals, polymers, and ceramics.

Cemented carbides, best known for their superior wear resistance, have a range of industrial uses more diverse than that of any other powder metallurgy product including metalworking and mining tools and wear-resistant components. This article discusses raw materials and manufacturing methods used in the production of cemented carbides, the physical and mechanical properties of carbides, and wear mechanisms encountered in service. Emphasis is placed on tungsten carbide-cobalt (WC-Co) or tungsten carbide-nickel (WC-Ni) materials as used in nonmachining applications. Nominal composition and properties of representative cemented carbide grades and their applications are listed in a table.

A sliding bearing (plain bearing) is a machine element designed to transmit loads or reaction forces to a shaft that rotates relative to the bearing. This article discusses the properties of bearing materials. It provides information on bearing material systems: single-metal systems, bimetal systems, and trimetal systems. The article describes the designations, nominal compositions, mechanical properties, and applications of various sliding bearing alloys: tin-base alloys, lead-base alloys, copper-base alloys, aluminum-base alloys, silver-base alloys, zinc-base alloys, additional metallic materials, nonmetallic materials. It describes casting processes, powder metallurgy processes, and electroplating processes. The article also discusses the selection criteria for bearing materials.

Tool steels are carbon, alloy, and high-speed steels that can be hardened and tempered to high hardness and strength values. This article discusses the classifications of commonly used tool steels: water-hardening tool steels, shock-resisting tool steels, cold-work tool steels, and hot-work tool steels. It describes four basic mechanisms of tool steel wear: abrasion, adhesion, corrosion, and contact fatigue wear. The article describes the factors to be considered in the selection of lubrication systems for tool steel applications. It also discusses the surface treatments for tool steels: carburizing, nitriding, ion or plasma nitriding, oxidation, boriding, plating, chemical vapor deposition, and physical vapor deposition. The article describes the properties of high-speed tool steels. It summarizes the important attributes required of dies and the properties of the various materials that make them suitable for particular applications. The article concludes by providing information on abrasive wear and grindability of powder metallurgy steels.

This article discusses the pressing and sintering of various refractory metal powders for the production of intermediate products as well as special cases of finished products. The metal powders considered include tungsten, molybdenum, tantalum, niobium and their alloys, as well as rhenium.

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.

Powder metallurgy (PM) has been called a lost art. Long before furnaces were developed that could approach the melting point of metal, PM principles were used. This article provides an overview of the major historical developments of various methods of platinum powder production. The development of production methods took place in various phases starting from prehistoric time, post-war period, to recent and commercial period. The article discusses the powder metallurgy of platinum, as well as the commercial and post-war developments of PM. Literature and trade associations are also discussed.

This article provides an overview of the compaction of metal powder in a rigid die and reviews the compaction characteristics of stainless steel powders, including green density, compressibility, green strength, apparent density, flow rate, and sintered density. It describes the influence of compaction characteristics of stainless steel powders in tool materials selection, lubrication, annealing, double pressing/double sintering, and warm compaction.

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.