Stainless steel powder metallurgy (P/M) parts represent an important and growing segment of the P/M industry. This article describes the processing, properties, and composition of medium-density and high-density P/M stainless steels. Medium-density materials are processed by pressing and sintering prealloyed stainless powders. High-density materials are produced by hot isostatic pressing, cold isostatic pressing followed by extrusion, or metal injection molding. The comparison of mechanical properties of these P/M stainless steels is represented graphically. The article contains a table that lists the effect of iron, carbon, nitrogen, oxygen, and density on the corrosion resistance of the sintered austenitic stainless steels.

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 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.

This article reviews various segments of the powder metallurgy (PM) process from powder production and powder processing through the characterization of the materials and their properties. It covers the processing methods for consolidating metal powders including options for processing to full density. The article outlines the freeform fabrication process, also known as additive manufacturing and describes finishing operations of PM parts. It concludes with information on the applications of PM parts.

The technology to fabricate lower-density, porous powdered metal materials provides unique engineering solutions for many applications. This article summarizes the characteristics and applications of porous powder metallurgy technology, as well as the fabrication methods employed.

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.

Milling of materials, whether hard and brittle or soft and ductile, is of prime interest and of economic importance to the powder metallurgy (PM) industry. This article discusses the principles of milling, milling parameters, and the powder characteristics required for the process. It discusses the changes in powder particle morphology that occur during milling of metal powders produced by various processes such as microforging, fracturing, agglomeration, and deagglomeration. The article also provides useful information on milling equipment such as tumbler ball mills, vibratory ball mills, attrition mills, and hammer and rod mills.

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.

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.

This article discusses the characteristics, properties, and production methods of copper powders and copper alloy powders. Bulk of the discussion is devoted to production and applications of powder metallurgy (P/M) parts, including pure copper P/M parts, bronze P/M parts, brass and nickel silver P/M parts, copper-nickel P/M parts, copper-lead P/M parts, copper-base P/M friction materials, copper-base P/M electrical contact materials, copper-base P/M brush materials, infiltrated parts, and oxide-dispersion-strengthened copper P/M materials.

Friction materials are the components of a mechanism that converts mechanical energy into heat upon sliding contact. This article discusses the selection criteria, manufacturing process, and applications of friction powder metallurgy materials. It provides information on the manufacturing process of powder metallurgy friction materials through a process of mixing/blending, compacting, and sintering. The final machining that they undergo, to ensure that they meet dimensional specifications, is also discussed.

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.

Stainless steels are primarily alloys of iron and chromium. They are grouped into five families, primarily based on their microstructure: ferritic, austenitic, martensitic, duplex, and precipitation hardening. Three out of the five families of stainless steels, namely, austenitic, ferritic, and martensitic, are well suited for manufacture via conventional powder metallurgy (PM) processes. This article presents the iron-chromium partial phase diagram to illustrate the changes in the temperature range when pure iron is alloyed with chromium. It describes AISI and UNS numbering systems, which are used as an identification system for stainless steels. The article tabulates the material designations of stainless steels in accordance with the Metal Powder Industries Federation. It also details the characteristics and chemical composition of wrought and PM stainless steels.

This article describes the capabilities, limitations, advantages, and disadvantages of the powder metallurgy (PM) gear manufacturing process. It discusses the types of gears that can be produced by PM and presents the design guidelines for PM gears. The article provides information on gear tolerances and performance of PM gears. It also explains various procedures to inspect and test the mechanical properties, dimensional specifications, and surface durability (hardness).

This article briefly reviews the subject of copper-base powder-metallurgy (P/M) products in terms of powder production methods (atomization, oxide reduction, electrolysis, and hydrometallurgy) and the product properties/consolidation practices of the major applications. Of the four major methods for making copper and copper alloy powders, atomization and oxide reduction are presently practiced on a large scale in North America. The article provides information on the mechanism, production, properties, composition and applications of different types of copper-base P/M products, including self-lubricating sintered bearings, structural parts, oxide-dispersion-strengthened copper, sintered metal friction materials, and porous filters.

This article focuses on mechanical testing characterization of blended elemental powder metallurgy (PM) titanium alloys and prealloyed PM titanium alloys. It examines the tensile properties, fracture toughness, stress-corrosion threshold resistance, fatigue strength, crack propagation properties, and processing-microstructure-property relationships of these alloys. The article also reviews five considerations for powder process selection.

Atomization is the dominant method for producing metal and prealloyed powders from aluminum, brass, iron, low-alloy steels, stainless steels, tool steels, superalloys, titanium alloys, and other alloys. The general types of atomization processes encompass a number of industrial and research methods. This article describes the key process variables and production factors for the industrial methods: two-fluid, centrifugal, vacuum or soluble-gas, and ultrasonic atomization. It also reviews the effect of atomization methods and process variables on key powder characteristics such as the average particle size, particle size distribution or screen analysis, particle shape, chemical composition, and microstructure.

This article uses metal and alloy powders as examples to briefly discuss how to perform the characterization of powders. It begins by reviewing some of the techniques involved in the sampling of powders to ensure accurate characterization. This is followed by a discussion on the important properties to characterize powders, namely the particle size, surface area, density, porosity, particle hardness, compressibility, green strength, and flowability. For characterization of powders, both individual particles and bulk powders are used to evaluate their physical and chemical properties. The article also discusses the important characteristics and compositions of powder as well as impurities that directly affect powder properties. It ends with a description of the ignition and dust-explosion characteristics of organic and metal powders.

This article provides information on the process details that differ from general water atomization of metals as they relate to basic and engineering properties that are specific to stainless steel powders. The discussion focuses on the compacting-grade stainless steel powders. The process details include raw materials, melting method, and control of physical and chemical powder characteristics. The article describes the gas atomization of stainless steel powders and processes that are done after water atomization: drying, screening, annealing, and lubricating. It also discusses the two types of quality assurance testing measures for powder metallurgy stainless steels: tests for powder contamination and tests of chemical and physical properties.

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.