Search Results for field-assisted sintering

This chapter discusses the growing role of powder metallurgy in the production of intermetallic, Heusler, and high-entropy alloys. It reviews the challenges of producing these materials by conventional methods and the advantages of sinter-based PM techniques. It explains why PM processes are better suited for complex materials than casting and compares the properties of intermetallic, Heusler, and high-entropy alloys prepared by casting and powder-metal techniques.

This chapter covers various consolidation techniques used in powder metallurgy, including laser sintering (pressureless sintering), hot pressing, high-pressure torsion, microwave sintering, spark plasma sintering, and pulse plasma sintering. It also discusses the effect of milling parameters on mechanically alloyed powders, their consolidation characteristics, and the properties of bulk components.

This chapter explains how powder metallurgy technologies are being leveraged for the production of automotive components, electric motors, rare-earth permanent magnets, and the infrastructure for high-speed rail transport.

This chapter discusses the economic importance of powder metallurgy in various countries, the types of jobs created, and the role of powder metallurgy associations around the world.

This chapter provides an overview of sintering techniques and the microstructures and properties that can be achieved in different material systems. It covers conventional furnace sintering, microwave and laser sintering, hot and hot-isostatic pressing, and spark plasma sintering. It describes the advantages and disadvantages of each method, the mechanisms involved, and the effect of sintering parameters on the density, grain size, and mechanical properties of titanium and tungsten heavy alloys, stainless steel, cemented carbides, ceramics, composites, and rare earth magnets.

This article discusses the compositions, structures, and properties of the most common grades of soft magnetic metals and permanent magnet alloys. It explains how alloying additions and impurities affect the magnetic properties of these materials, which include commercially pure and phosphorus irons, low-carbon and silicon steels, ferritic stainless steels, and nickel-iron and iron-cobalt alloys.

This chapter is intended to identify materials, processes, and designs that will lead to great advances in powder-binder forming technologies. It discusses some of the structures obtained through these advances in powder-binder technologies such as binder jetting and extrusion-based additive manufacturing, including bound-metal deposition and fused-filament fabrication: oxidation-resistant high-temperature alloys, anisotropic structures, submicrometer-scale structures, surface hard materials, and artist metallic clays. Some of the advances discussed include the developments in process involving plastics, emulsions, ceramics, and porous structures and foams. Improvements in the design processes have led to the development of functional structures, controlled porosity, and bioinspired structures.

This chapter discusses the advantages and disadvantages of producing titanium parts using powder metallurgy (PM) techniques. It compares the typical properties of wrought, cast, and PM titanium alloy products, addresses various manufacturing challenges, and describes several consolidation and shaping processes along with associated property data.

This chapter introduces the key powder fabrication attributes to assist in the identification of the right powders for an application. First, it describes the characteristics of engineering powders such as particle size distribution, powder shape and packing density, surface area, powder flow and rheology, and chemical analysis. The chapter then describes the general categories of powder fabrication methods, namely mechanical comminution, electrochemical precipitation, thermochemical reaction, and phase change and atomization. It provides information on the two largest contributors to powder price, namely raw material cost and conversion cost. The applicability of various processes to specific material systems is mentioned throughout this chapter.

This chapter provides details on powder-binder processing for three materials, namely precipitation-hardened 17-4 PH stainless steel, cemented carbides, and alumina. The types of powders, binders, feedstock, shaping processes, debinding, sintering cycles, compositions, microstructure, distortion, postsintering treatments, and mechanical properties are presented for each. The shaping options include powder-binder approaches such as binder jetting, injection molding, extrusion, slip and slurry casting, centrifugal casting, tape casting, and additive manufacturing. Sintering options are outlined with respect to attaining high final properties.

After shaping and first-stage binder removal, the component (with remaining backbone binder) is heated to the sintering temperature. Further heating induces densification, evident as dimensional shrinkage, pore rounding, and improved strength. This chapter begins with a discussion on the events that are contributing to sintering densification, followed by a discussion on the driving forces, such as surface energy, and high-temperature atomic motion as well as the factors affecting these processes. The process of microstructure evolution in sintering is then described, followed by a discussion on the tools used for measuring bulk properties to monitor sintering and density. The effects of key parameters, such as particle size, oxygen content, sintering atmosphere, and peak temperature, on the sintered properties are discussed. Further, the chapter covers sintering cycles and sintering practices adopted as well as provides information on dimensional control and related concerns of sintering. Cost issues associated with sintering are finally covered.

This chapter assesses the state of 3D printing among automakers, medical device manufacturers, and construction companies.

Powder metallurgy (P/M) is a flexible metalworking process for the production of gears. The P/M process is capable of producing close tolerance gears with strengths to 1240 MPa at economical prices in higher volume quantities. This chapter discusses the capabilities, limitations, process advantages, forms, tolerances, design, tooling, performance, quality control, and inspection of P/M gear manufacture. In addition, it presents examples that illustrate the versatility of the P/M process for gear manufacture.

This chapter discusses coating technologies that are applicable to beryllium, including physical and chemical vapor deposition, thermal evaporation, electroplating, sputtering, ion plating, and plasma arc spraying. It describes the advantages and disadvantages of each method and the effect of temperature, pressure, and other process variables on the microstructures and properties developed.

This chapter discusses the growing use of sintered stainless steels in automotive applications and various types of filters and filtering media. It also describes how these materials are produced in the form of metal foams and cellular structures and how they serve as flake pigments in corrosion-resistant coatings.

The physical properties of a material are those properties that can be measured or characterized without the application of force and without changing material identity. This chapter discusses in detail the common physical properties of metals, namely density, electrical properties, thermal properties, magnetic properties, and optical properties. Some physical properties for a number of metals are given in a table.

This chapter provides details on several specific binder formulations and a discussion of basic binder design concepts. The focus is on customization of the feedstock response to heating, pressurization, or solvent exposure for a specific shaping process. The discussion starts with the requirements of a binder system, the historical progression of binder formulations, and the use of binder alternatives to adapt to specific applications. The importance of binder handling strength to shape preservation is emphasized. The chapter provides information on the binders used for room-temperature shaping, namely slurry and tape casting systems.

Powder metallurgy plays a central role in the production of nearly all beryllium components. This chapter describes the primary steps in the powder metal process and the work that has been done to improve each one. It explains how beryllium powders are made and how they are consolidated prior to sintering. It also compares and contrasts the properties of beryllium products made using different methods and provides composition and particle size data on commercially available powders.

This chapter discusses the application of high-pressure cold spray to the automotive industry field, with special attention to three applications: additive manufacturing, fabrication methods, and protective coatings. Various studies on the automotive application of cold spray are reviewed. The background and purpose of each application are presented and practical cases are discussed.

This chapter examines the microstructure and properties of annealed and normalized steels containing more than 0.25% carbon. It shows, using detailed micrographs, how incrementally higher levels of carbon affect the structure and distribution of pearlite and how it intermingles with proeutectoid ferrite and cementite. It explains how ferrite and pearlite respond to deformation and how related features such as slip lines, dislocations, shear bands, and kinking can be detected as well as what they reveal. It also describes the structure of patented wires, cast steels, and sintered steels and the morphology of manganese sulfide inclusions in castings.