Search Results for unsintered particles

This article describes several factors, which help in determining the compressibility of metal powders: particle shape, density, composition, hardness, particle size, lubrication, and compacting. It discusses the uses of annealing metal powders and describes compressibility testing of the powders. The article details green strength and its mechanism and the variables affecting the strength. It also discusses two test methods for determining the green strength: the Rattler test and the transverse bend test.

Ceramics are materials with the potential for a wide range of high-speed finishing operations and for high removal rate machining of difficult-to-machine materials. This article describes the production process, composition, properties, and applications of ceramic tool materials. It presents a comprehensive discussion on the properties and composition of alumina-base tool materials, including alumina and titanium carbide, alumina-zirconia, and silicon carbide whisker reinforced alumina, and silicon nitride base tool materials.

This article provides information on the microstructure of powder metal alloys and the special handling requirements of porous materials. It covers selection, sectioning, mounting, grinding, and polishing, and describes procedures, such as washing, liquid removal, and impregnation, meant to preserve pore structures and keep them open for analysis. The article compares and contrasts the microstructures of nearly 50 powder metal alloys, using them to illustrate the effect of consolidation and compaction methods as well as particle size, composition, and shape. It discusses imaging equipment and techniques and provides data on etchants and etching procedures.

This article describes the unique aspects of cold isostatic pressing (CIP) in comparison with die compaction, for powder metallurgy parts. It details the components of CIP equipment, including pressure vessels, pressure generators, and tooling material. The article reviews the part shapes and their influence in determining tap density of the filled mold. It provides a discussion on process parameters, such as dwell time, depressurization rate, evaluation of green strength and density, and thermal processing, and illustrates a process flowchart for the production of CIP parts.

Powder metallurgy is a near-net shape process capable of producing complex parts with little or no need for secondary operations such as machining, joining, or assembly. However, the inability to produce certain geometrical figures such as transverse holes, undercuts, and threads frequently necessitates some machining, particularly drilling. This article provides a discussion on the measures that can optimize the machining of P/M materials. It reviews the factors influencing machinability of P/M components, including workpiece and tool material properties, cutting conditions, machine and cutting tool parameters as well as some P/M material and production process parameters. These parameters discussed include the particle size, part geometry, porosity, compaction and sintering methods. In addition, the article presents guidelines for the various machining processes, namely, turning and boring, milling, drilling, grinding, reaming, burnishing, tapping, and honing and lapping.

This article provides an overview of the concepts of environmental, health, and safety (EH&S) risk incidents, then discusses these concepts relative to additive manufacturing (AM): the multiple intrants, process parameters, and equipment, as well as the resulting products and wastes. The article discusses additive manufacturing hazards, which are broken down into material hazards, equipment/process hazards, and facility hazards. The environmental impact of AM and the development of EH&S standards for AM also are covered in the article.

According to International Organization for Standardization (ISO)/ASTM International 52900, additive manufacturing (AM) can be classified into material extrusion, material jetting, vat photo polymerization, binder jetting, sheet lamination, powder-bed fusion (PBF), and directed-energy deposition. This article discusses the processes involved in polymer powder 3D printing using laser fusion/ sintering and fusing agents and energy, as well as the thermally fused PBF. It provides information on polymer powder parameters and modeling, the powder-handling system, powder characterization, the flowability of powder feedstock, and polymer part characteristics. The article describes the types of polymers in PBF, the processes involved in powder recycling, and the prospects of PBF in AM. In addition, the biomedical application of polyether ether ketone (PEEK) is also covered.

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.

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 begins with a discussion on general powder metallurgy design considerations that assist in the selection of the appropriate processing method. It reviews powder processing techniques, conventional press-and-sinter methods, and full-density processes to understand the design restrictions of each powder processing method. The article provides comparison of powder processing methods based on their similarities, differences, advantages, and disadvantages. It concludes with a discussion on design issues for the components of powder processing technologies.

Certain metal products can be produced only by powder metallurgy; among these products are materials whose porosity is controlled. Successful production by powder metallurgy depends on the proper selection and control of process variables: powder characteristics; powder preparation; type of compacting press; design of compacting tools and dies; type of sintering furnace; composition of the sintering atmosphere; choice of production cycle, including sintering time and temperature; and secondary operations and heat treatment. When the application of a powder metallurgy part requires high levels of strength, toughness, or hardness, the mechanical properties can be improved or modified by infiltration, heat treatment, or a secondary mechanical forming operation such as cold re-pressing or powder forging. The article also discusses the effect of the secondary processes on P/M mechanical properties.

This article provides information on the most frequently used atmospheres in commercial sintering of powder metallurgy iron and steel materials. These include endothermic, exothermic, dissociated ammonia, pure hydrogen, and nitrogen-base atmospheres. The article discusses sintering of iron and iron-graphite powder, iron-copper and iron-copper graphite, and alloy steels. The effects of various sinter conditions on the amount of combined carbon formed in the steel are also discussed. The article concludes with information on high-temperature sintering and sinter hardening.

The organizations that are most active in the development of standards for powder metallurgy (PM) are the American Society for Testing and Materials (ASTM), Metal Powder Industries Federation (MPIF), and International Standards Organization (ISO). This article presents the test method standards, materials standards, and material designation codes for PM materials. It provides information on the codes for structural parts, PM soft magnetic materials, PM self-lubricating bearings, metal injection molded materials, and powder forged materials.

Powder forging is a process in which unsintered, presintered, and sintered powder metallurgy preforms are hot formed in confined dies. This article provides information on the basic forms of powder forging and describes the material considerations, process considerations, and mechanical properties of powder forged (PF) steels. It reviews the parameters involved in quality assurance tests for PF parts. The article includes examples of PF components and highlights the reasons for selecting them over those made by competing forming methods.

Powder forging is an extension of the conventional press and sinter powder metallurgy process, which is recognized as an effective technology for producing a variety of parts to net or near-net shape. This article focuses on the material considerations, such as powder characteristics, alloy development, and inclusion assessment; and process considerations, such as process stages, tool design, and secondary operations; of ferrous alloy powder forging. The mechanical properties of powder forged materials are also reviewed. The article discusses the quality assurance tests for powder forged materials: the part dimensions and surface finish measurement, magnetic particle inspection, metallographic analysis, and nondestructive testing. It concludes with a discussion on the applications of powder forged parts with examples.

The large majority of the commercially important glasses are processed from a carefully calculated batch of raw materials that is then melted in special furnaces. Providing an introduction to melting practices of glass production, this article focuses on various finishing methods of glass products, including forming, grinding and polishing, and explores the advantages, disadvantages and steps involved in sol-gel process. It also discusses the types, processes and properties of annealed, laminated, and tempered glass, and presents the steps involved in glass decoration. The article gives a detailed account of production, properties and application of fiberglass, optical fibers, glass spheres and ceramic glasses, and describes the forms, classification, compositions and properties of glass/metal and glass-ceramic/metal seals.

Powder-bed fusion (PBF) is a group of additive manufacturing (AM) processes that includes selective laser sintering, selective laser melting, and electron beam melting. This article explains the processes and parameters of PBF systems that are used for biomedical applications. It also presents the desirable properties of biomedical devices and the advantages of using PBF systems for biomedical applications.