Search Results for activated sintering

Sintering is a thermal treatment process in which a powder or a porous material, already formed into the required shape, is converted into a useful article with the requisite microstructure. Sintering can be classified as solid-state, viscous, liquid-phase, and pressure-assisted (or pressure) sintering. This article provides information on the mechanisms and theoretical analysis of sintering and focuses on the types, mechanisms, process and microstructural variables, computer simulation, stages, and fundamentals of densification and grain growth of solid-state sintering and liquid-phase sintering. It describes the models for viscous sintering and the methods used in pressure-assisted sintering, namely, uniaxial hot pressing, hot isostatic pressing, sinter forging, and spark plasma sintering.

High-temperature sintering of ferrous components continues to be important in the powder metallurgy (PM) industry. Improvements in both production rates and properties are possible as sintering temperatures increase above 1120 deg C. This article provides an overview of the different various stages of the sintering process and the physical, chemical, and metallurgical phenomena occur within the mass of metal powder particles. It discusses the four advantages of high-temperature sintering of various ferrous PM materials: improved mechanical properties, improved physical properties, development of liquid phase, and ability to sinter active elements in alloy steels. The article also provides information on three sources of process control requirements, namely, the powder blend, green density, and sintering conditions.

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.

The plasma carburizing process is basically a low-pressure carburizing process making use of a high-voltage electrical field applied between the load to be treated and the furnace wall producing activated and ionized gas species responsible for carbon transfer to the workpieces. This article begins with an overview of the theoretical background and the range and limitations of glow-discharge plasma. It describes the plasma carburizing process, which is carried out with methane or propane. Plasma carburizing processes of sinter metals and stainless steels, and the influence of current pulse length on carbon input of low-pressure carburizing process are also described. The article presents the basic requirements and process parameters to be considered in plasma carburizing equipment. It also exemplifies a still-working plasma process in industrial measure.

The application of three-dimensional printers can be revolutionary as a tool for the customization and personalization of pharmaceutical dosage forms. The areas of 3D printing applicable to pharmaceutical manufacturing can be segregated into three categories: extrusion technologies, powder-bed fusion, and stereolithography. Common extrusion-based technologies are fused deposition modeling and pressure-assisted microsyringe; powder-bed fusion is separated by binder jet and selective laser sintering. The synergies between pharmaceutical, or active pharmaceutical ingredient (API), and polymer printing are discussed in this article, with particular attention to how the incorporation of small-molecule APIs changes the material selection, design considerations, processing parameters, and challenges associated with each technology.

Bronze and brass alloys are two key classes of materials in copper-base powder metallurgy applications. They are often compacted using mechanical or hydraulic pressing machines. This article provides an overview of the powder pressing process, providing information on the powder properties of bronze and brass and the roles of lubricant and compaction dies in the pressing process. It discusses the structural defects that originate during the compaction process. The article also describes the major factors that influence the sintering response in bronze, prealloyed bronze, brass, and nickel-silver.

Consolidation of titanium powders at room temperature may be performed by low-cost conventional powder metallurgy processes. This article provides information on various consolidation methods, namely, die pressing, direct powder rolling, and cold isostatic pressing. It also describes the sintering of blended elemental powders, high-strength titanium alloys, and porous material as well as the sintering of titanium powders by microwave heating.

Sintering atmosphere protects metal parts from the effects of contact with air and provides sufficient conduction and convection for uniform heat transfer to ensure even heating or cooling within various furnace sections, such as preparation, sintering, initial cooling, and final cooling sections. This article provides information on the different zones of these furnace sections. It describes the types of atmospheres used in sintering, namely, endothermic gas, exothermic gas, dissociated ammonia, hydrogen, and vacuum. The article concludes with a discussion on the furnace zoning concept and the problems that arise when these atmospheres are not controlled.

This article discusses two major sintering methods: pressureless and pressure-assisted sintering. Pressureless sintering techniques include vacuum and partial-pressure, hydrogen, and microwave sintering. Pressure-assisted consolidation techniques include overpressure sintering, sintering followed by postsinter hot isostatic pressing, hot pressing, and several rapid hot consolidation techniques. The article describes nitrogen sintering and the sintering of cermets. It reviews the furnaces used for sintering and presents the lubrication removal techniques. The article also outlines the need to control carbon and oxygen to obtain optimal properties and explains microstructure development and grain size control.

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 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.

Many applications of ceramics and glasses require them to be joined to each other or to other materials such as metals. This article focuses on ceramic joining technologies, including glass-metal sealing, glass-ceramic/metal joining, ceramic-metal joining, ceramic-ceramic joining, and the more advanced joining of nonoxide ceramics. It also discusses metallizing, brazing, diffusion bonding, and chemical bonding.

This article is intended to assist the development of procedures for the brazing of ceramic-to-ceramic or ceramic-to-metal joints for service under elevated temperatures, mechanical or thermal stresses, or corrosive atmospheres. It describes the factors considered in preparing a procedure for the brazing of graphitic materials.

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.

This article provides a detailed discussion on the most commonly employed tests and specific examples of the use of these tests in evaluating the corrosion resistance of powder metallurgy (P/M) stainless steels. It describes the influence of various processing parameters on the corrosion resistance of P/M stainless steels. The approaches used to improve the corrosion resistance of sintered stainless steels are discussed briefly. The article also presents a discussion on the manufacturing and corrosion characteristics of P/M superalloys.