This chapter reviews failure aspects of structural ferrous powder metallurgy (PM) parts, which form the bulk of the PM industry. The focus is on conventional PM technology of parts in the density range of 6 to 7.2 g/cc. The chapter briefly introduces the processing steps that are essential to understanding failure analysis of PM parts. This is followed by a section on case hardening of PM parts. The methods used for analyzing the failures are then discussed. Some case studies are given that illustrate different failures and the methods of prevention of these failures.

This chapter discusses the methods by which stainless steel powders are shaped and compacted prior to sintering, including rigid die compaction, metal injection molding, extrusion, and hot isostatic pressing. It explains where each process is used and how processing parameters, such as temperature and pressure, and powder characteristics, such as particle size and shape, influence the quality of manufactured parts. It describes the various stages of metal powder compaction, the role of lubricants, and how to account for dimensional changes in the design of tooling and process sequences.

This chapter explains the basic terminology and principles of metallurgy as they apply to extrusion. It begins with an overview of crystal structure in metals and alloys, including crystal defects and orientation. This is followed by sections discussing the development of the continuous cast microstructure of aluminum and copper alloys. The discussion provides information on billet and grain segregation and defects in continuous casting. The chapter then discusses the processes involved in the deformation of pure metals and alloys at room temperature. Next, it describes the characteristics of pure metals and alloys at higher temperatures. The processes involved in extrusion are then covered. The chapter provides details on how the toughness and fracture characteristics of metals and alloys affect the extrusion process. The weld seams in hollow profiles, the production of composite profiles, and the processing of composite materials, as well as the extrusion of metal powders, are discussed. The chapter ends with a discussion on the factors that define the extrudability of metallic materials and how these attributes are characterized.

This chapter describes the processes involved in alloy production, including melting, casting, solidification, and fabrication. It discusses the effects of alloying on solidification, the formation of solidification structures, supercooling, nucleation, and grain growth. It describes the design and operation of melting furnaces as well as melting practices and the role of fluxing. It also discusses casting methods, nonferrous casting alloys, and atomization processes used to make metal powders.

This chapter provides information on the properties and behaviors of stainless steels and stainless steel powders. It begins with a review of alloy designation systems and grades by which stainless steels are defined. It then describes the composition, metallurgy, and engineering characteristics of austenitic, ferritic, martensitic, duplex, and precipitation hardening stainless steel powders and metal injection molding grades.

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 appendix is a compilation of terms and definitions associated with the processing, microstructure, and properties of powder metal stainless steels.

This chapter discusses the mechanical properties of powder metal stainless steels and the extent to which they can be controlled through appropriate alloying and processing steps. It describes how process-related factors, such as porosity, interstitial content, sintering atmosphere, and heating and cooling profiles, affect strength, ductility, and corrosion resistance. It also provides an extensive amount of property data – including tensile and yield strength, elongation, hardness, and creep and stress rupture measurements as well as fatigue curves – for various grades of powder metal stainless steel.

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.

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 describes secondary processes employed in the production of powder-metal stainless steel parts, including various machining operations, welding, brazing, sinter bonding, resin impregnation, re-pressing and sizing, and surface finishing. It also discusses the factors that affect the machinability and weldability of sintered stainless steels.

Compared with other deformation processes used to produce semifinished products, the hot-working extrusion process has the advantage of applying pure compressive forces in all three force directions, enhancing workability. The available variations in the extrusion process enable a wide spectrum of materials to be extruded. This chapter focuses on the processes involved in the extrusion of semifinished products in various metals and their alloys, namely tin, lead, lead-base soft solders, tin-base soft solders, zinc, magnesium, aluminum, copper, titanium, zirconium, iron, nickel, and powder metals. It discusses their properties and applications as well as suitable equipment for extrusion. It further discusses the processes involved in the extrusion of semifinished products in exotic alloys and extrusion of semifinished products from metallic composite materials.

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.

This chapter discusses the advantages and disadvantages of metal matrix composites and the methods used to produce them. It begins with a review of the composition and properties of aluminum matrix composites. It then describes discontinuous composite processing methods, including stir and slurry casting, liquid metal infiltration, spray deposition, powder metallurgy, extrusion, hot rolling, and forging. The chapter also provides information on continuous-fiber aluminum and titanium composites as well as particle-reinforced titanium and fiber metal (glass aluminum) laminates.

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.

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.

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.

Stainless steel powders are usually made by water or gas atomization. This chapter describes both processes and the properties and characteristics of the powders they produce. It also discusses secondary processes, including drying, screening, annealing, and lubricating, and the effects of iron contamination on corrosion resistance.

This chapter discusses the sintering process for stainless steel powders and its influence on corrosion resistance. It begins with a review of sintering furnaces and atmospheres and the effect of temperature and density on compact properties such as conductivity, ductility, and strength. It then describes the relationship between sintered density and corrosion resistance and how it varies for different types of powders and operating environments. The chapter also explains how stainless steel powders respond to different sintering atmospheres, including hydrogen, hydrogen-nitrogen, and vacuum, and liquid-phase sintering processes.