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 describes the processes involved in the fabrication of wrought and cast metal products. It discusses deformation processes including bending and forming, material removal processes such as milling, cutting, and grinding, and joining methods including welding, soldering, and brazing. It also discusses powder consolidation, rolling, drawing and extrusion, and common forging methods.

The vast majority of beryllium products are manufactured from blocks, forms, or billets of compacted powder that are machined or worked into shape. This chapter describes the metalworking processes used, including rolling, forming, forging, extrusion, drawing, and spinning. It covers the qualitative and quantitative aspects of each process and provides examples showing how they are implemented and the results that can be achieved. The chapter also discusses the issue of beryllium’s low formability and describes some of the advancements that have been made in near-net shape processing.

This chapter covers the basic steps of the powder metallurgy process, including powder manufacture, powder blending, compacting, and sintering. It identifies important powder characteristics such as particle size, size distribution, particle shape, and purity. It compares and contrasts mechanical, chemical, electrochemical, and atomizing processes used in powder production, discusses powder treatments, and describes consolidation techniques along with secondary operations used to obtain special properties or improve dimensional precision. It also discusses common defects such as ejection cracks, density variations, and microlaminations.

This chapter describes some of the more typical manufacturing practices, along with their benefits and limitations. The manufacturing practices covered include primary melting, electroslag remelting, rolling, hot and cold drawing, and continuous casting. The chapter discusses the advance and application of powder metallurgy. A few of the more recently introduced processes that hold considerable promise for producing tool steels or finished tools at a lower cost or with improved quality also are reviewed.

Gas turbine disks made from nickel-base superalloys are often produced using powder metallurgy (P/M) techniques because the alloy compositions normally used are difficult or impractical to forge by conventional methods. This chapter discusses the P/M process and its application to superalloys. It describes the gas, vacuum, and centrifugal atomization processes used to make commercial superalloy powders. It explains how the powders are consolidated into preforms or billets using hot isostatic pressing, extrusion, or a combination of the two. It also provides information on spray forming and consolidation by atmospheric pressure, and includes a section on powder-based disk components, where it discusses the general advantages of P/M as well as the effects of inclusions, carbon contamination, and the formation of oxide and carbide films due to prior particle boundary conditions. The chapter concludes with a detailed discussion on mechanically alloyed superalloy compositions, the product forms into which they are made, and some of the applications where they are used.

This chapter explains that the key to forging is understanding and controlling metal flow and influential factors such as tool geometry, the mechanics of interface friction, material characteristics, and thermal conditions in the deformation zone. It also reviews common forging processes, including closed-die forging, extrusion, electrical upsetting, radial forging, hobbing, isothermal forging, open-die forging, orbital forging, and coining.

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.

Superalloys are nickel, iron-nickel, and cobalt-base alloys designed for high-temperature applications, generally above 540 deg C. This chapter covers the metallurgy, composition, and properties of cast and wrought superalloys. It provides information on melting, heat treating, and secondary fabrication processes. It also covers coating technology, including aluminide diffusion and overlay coatings, and addresses the advantages and disadvantages of superalloys in various applications.

In forgings of both ferrous and nonferrous metals, the flaws that most often occur are caused by conditions that exist in the ingot, by subsequent hot working of the ingot or the billet, and by hot or cold working during forging. The inspection methods most commonly used to detect these flaws include visual, magnetic particle, liquid penetrant, ultrasonic, eddy current, and radiographic inspection. This chapter provides a detailed discussion on the characteristics, process steps, applications, advantages, and limitations of these methods. It also describes the flaws caused by the forging operation and the principal factors that influence the selection of a nondestructive inspection method for forgings.

This chapter examines the process, structure, and property relationships in titanium alloys. It provides information on microstructures and strengthening mechanisms, the role of alloy and interstitial elements, and the effect of composition, processing, and surface treatments on tensile and yield strength, fracture toughness, hardness, ductility, and creep and fatigue behaviors. The chapter covers wrought, cast, and powder metal titanium alloys and contains an extensive amount of property data.

This appendix includes contact information for titanium manufacturers, suppliers, and service providers.

Titanium aluminides are lightweight materials that have relatively high melting points and good high-temperature strength. They also tend to be stronger and lighter than conventional titanium alloys, but considerably less ductile. This chapter begins with a review of the titanium-aluminum phase diagram, focusing on the properties, compositions, and microstructures of alpha-2 Ti3Al alloys. It then describes the properties, microstructures, and compositions of orthorhombic, gamma, and near-gamma alloys as well as the processing methods and procedures normally used in their production.

This appendix includes selected references on topics related to the production and application of superalloys, including properties and microstructure; melting/ingot breakdown; forging/powder metallurgy; machining, heat treating, joining, refurbishment/repair; investment casting; coatings/corrosion; and modeling.

This chapter discusses the similarities and differences of forging and forming processes used in the production of wrought superalloy parts. Although forming is rarely concerned with microstructure, forging processes are often designed with microstructure in mind. Besides shaping, the objectives of forging may include grain refinement, control of second-phase morphology, controlled grain flow, and the achievement of specific microstructures and properties. The chapter explains how these objectives can be met by managing work energy via temperature and deformation control. It also discusses the forgeability of alloys, addresses problems and practical issues, and describes the forging of gas turbine disks. On the topic of forming, the chapter discusses the processes involved, the role of alloying elements, and the effect of alloy condition on formability. It addresses practical concerns such as forming speed, rolling direction, rerolling, and heat treating precipitation-hardened alloys. It presents several application examples involving carbide-hardened cobalt-base and other superalloys, and it concludes with a discussion on superplasticity and its adaptation to commercial forging and forming operations.

This chapter discusses the processes of isothermal and hot-die forging and their use in producing aerospace components. It explains how isothermal forging was developed to provide a near-net shape component geometry and well-controlled microstructures and properties with accurate control of the working temperature and strain rate. It describes the materials typically used as well as equipment and tooling, die heating procedures, part separation techniques, and postforging heat treatment.

Titanium is a lightweight metal used in a growing number of applications for its strength, toughness, stiffness, corrosion resistance, biocompatibility, and high-temperature operating characteristics. This chapter discusses the applications, metallurgy, properties, compositions, and grades of commercially pure titanium and alpha and near-alpha, alpha-beta, and beta titanium alloys. It describes primary and secondary fabrication processes, including melting, forging, forming, heat treating, casting, machining, and joining as well as powder metallurgy and direct metal deposition. It also compares and contrasts the properties of wrought, cast, and powder metal titanium products and discusses corrosion behaviors.

Casting is the most economical processing route for producing titanium parts, and unlike most metals, the properties of cast titanium are on par with those of wrought. This chapter covers titanium melting and casting practices -- including vacuum arc remelting, consumable electrode arc melting, electron beam hearth melting, rammed graphite mold casting, sand casting, investment casting, hot isostatic pressing, weld repair, and heat treatment -- along with related equipment, process challenges, and achievable properties and microstructures. It also explains how titanium parts are produced from powders and how the different methods compare with each other and with conventional production techniques. The methods covered include powder injection molding, spray forming, additive manufacturing, blended elemental processing, and rapid solidification.