Search Results for high-temperature 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 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.

This article describes the sintering behavior of austenitic, ferritic, and martensitic stainless steels. It presents different sintering schedules that are selected by Metal Powder Industries Federation (MPIF). The article provides information on the equipment and atmospheres used for sintering and the steps involved in the process. It discusses the factors that influence the dimensional changes in sintering, namely, powder-related, compaction-related, and sintering-related factors.

Powder metallurgy (PM) stainless steels, as with conventional PM steels, are often used in the as-sintered condition. In addition to cost considerations, minimization of postsinter handling and secondary operations is also preferred because it reduces the potential for contamination of the parts with particulates and residues, which can result in the appearance of surface rust. This article provides information on various secondary operations, including tumbling, re-pressing, resin impregnation, annealing or heat treating, brazing, machining, and welding. It describes those aspects relating to welding of PM stainless steels, specifically, the effects of density, residual porosity, and sintered chemistry on weldability. Further, the article investigates the influence the sintering atmosphere has on machinability, as well as differences created by the presence of residual porosity.

Powder metallurgy (PM) techniques are effective in making magnetically soft components for use in magnetic part applications. This article provides an account of the factors affecting magnetism, permeability, and hysteresis losses. It includes information on the magnetic properties of PM materials that are used in the magnetic part applications, namely, pure iron, phosphorus irons, ferritic stainless steels, 50 nickel-50 iron, and silicon irons. The article describes the factors that affect and optimize magnetic properties. It contains a table that lists the magnetic properties possible in metal injection molding parts. The article also discusses ferromagnetic cores used in alternating current applications and some permanent magnets, such as rare earth-cobalt magnets and neodymium-iron-boron (neo) magnets.

This article describes the factors influencing the room-temperature and elevated-temperature mechanical properties of powder metallurgy (PM) stainless steels. It contains tables that list the mechanical property specifications of the Metal Powder Industries Federation (MPIF) Standard 35.

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 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.

Powder metallurgy (PM) processes include press and sinter hardening, metal injection molding, powder forging, hot isostatic pressing, powder rolling, and spray forming. This article provides an overview of PM processing methods and general considerations of heat treatment of PM parts that are case-hardened to obtain higher hardness, wear, fatigue, and impact properties. It describes the effects of porosity on heat treatment, alloy content on PM hardenability, and starting material on homogenization of PM steels. The article describes the properties, following heat treatment, of low-alloy steels tempered at 175 ºC for one hour, and lists recommended quench and temper parameters to achieve good wear resistance and core strength based on different ranges of porosity.

Iron powders are the most widely used powder metallurgy (P/M) material for structural parts. This article reviews low to medium density iron and low-alloy steel parts produced by the pressing and sintering technology. It explains different powder production methods, including Hoeganaes process, Pyron process, atomization of liquid metal, thermal decomposition and the electrodeposition process for carbonyl and electrolytic iron powders. It describes the types of compaction and sintering, explaining their effects of processing with designations. Further, the article deals with the mechanical and physical properties of ferrous P/M materials, which may depend on certain factors, namely microstructure, porosity, density, infiltration, re-pressing, chemical composition, and heat treatment.

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.

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 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 reviews various test methods used for evaluating the corrosion resistance of powder metallurgy stainless steels. These include immersion testing, salt spray testing, and electrochemical testing. The article discusses the factors that affect corrosion resistance of sintered stainless steels: compaction-related factors, sintering-related factors, and effects of alloy composition. Corrosion resistance data for sintered stainless steels is provided.

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.

Ceramic-metal composites, or cermets, combine the heat and wear resistance of ceramics with the formability of metals, filling an application niche that includes cutting tools, brake pads, heat shields, and turbine components. This article examines a wide range of cermets, including oxide cermets, carbide and carbonitride cermets, boride cermets, and other refractory types. It describes the powder metallurgy process by which cermets are produced, examining each step from powder preparation to post treatment. It discusses forming and compacting, injection molding, extrusion, rolling, pressing, slip casting, and sintering. It also discusses fundamental concepts such as chemical bonding, chemical composition, microstructure, and the development of physical and mechanical properties.