This article addresses the cobalt and cobalt-base alloys most suited for aqueous environments and those suited for high temperatures. The performance of cobalt alloys in aqueous environments encountered in commercial applications is discussed. The article provides information on the environmental cracking resistance of the cobalt alloys. Three welding processes that are used for hardfacing with the high-carbon Co-Cr-W alloys, namely, oxyacetylene, gas tungsten arc, and plasma-transferred arc are also discussed. The article examines the effects of various modes of high-temperature corrosion. It describes the applications and fabrication of cobalt alloys for high-temperature service.

This article describes the effects of undissolved carbides formed by segregation of alloying elements on the hardness of the powder-metallurgical (PM) high-alloy tool steels (HATS). It explains the calculation of exact stoichiometric carbon content that depends on the required martensite hardness, amount of carbon forming alloying elements, types of undissolved carbides during austenitizing, and the densities of the carbides. Microhardness values for carbides in HATS are also listed.

Cobalt finds its use in various applications owing to its magnetic properties, corrosion resistance, wear resistance, and its strength at elevated temperatures. This article discusses the mining and processing of cobalt and cobalt alloys. It describes the types of cobalt alloys, including wear-resistant alloys, high-temperature alloys, corrosion-resistant alloys, and special-purpose alloys. The article provides data on the chemical composition, mechanical properties, and physical properties of these alloys. Further, it provides information on the uses of cobalt in superalloys, cemented carbides, magnetic materials, low-expansion alloys, and high-speed tool steels.

Traditional processing methods for the part production of Co-Cr alloys include casting, powder metallurgy, and metal forming. However, the steps involved during materials processing followed by metal forming and machining are time consuming and fraught with processing variables. Three-dimensional (3D) printing enables rapid evolution in design, personalization, and so on. This article presents a brief description of some common additive manufacturing (AM) processes for the production of cobalt alloy parts, and provides a comparison between AM and conventional processing methods. The discussion is centered on process-microstructure-properties correlation in additively manufactured cobalt alloys and applications of these alloys.

Cobalt is used as an alloying element in alloys for various applications. This article provides a detailed account of the metallurgy of cobalt-base alloys. It focuses on the compositions, properties, and applications of cobalt-base alloys, which include wear-resistant cobalt alloys, heat-resistant cobalt alloys, and cobalt-base corrosion-resistant alloys. The article also describes the heat treatments such as annealing and aging, for these alloys.

This article describes the metallurgy and microstructure of high-performance cobalt-base alloys. It discusses metallographic preparation procedures, including sectioning, mounting, grinding, polishing, etching, staining, and heat tinting. It examines the microstructure of cobalt alloys in cast, wrought, and powder metal forms, including magnetic alloys as well as several cobalt-base superalloys.

This article provides a brief introduction to abrasive wear-resistant coating materials that contain a large amount of hard phases, such as borides, carbides, or carboborides. It describes some of the commonly used methods of producing thick wear-resistant coatings. The article also provides information on metal-matrix composites and cemented carbides. The three base-alloying concepts, including cobalt-, iron-, and nickel-base alloys used for wear-protection applications, are also described. The article compares the tribomechanical properties of the materials in a qualitative manner, thus allowing a rough materials selection for practitioners. It presents a brief discussion on hot isostatic pressing (HIP) cladding, sinter cladding, and manufacturing of thick wear-resistant coatings by extrusion or ring rolling. The article also discusses the processing sequence of thick wear-resistant coatings, namely, compound casting, deposition welding, and thermal spraying.

Understanding the high-temperature corrosion behavior of alloys is an important step toward the selection of appropriate alloys for process equipment. This article briefly describes the high-temperature corrosion modes that are frequently encountered in the chemical process industry. These modes include oxidation, carburization, metal dusting, nitridation, halogen corrosion, and sulfidation.

This article is a compilation of binary alloy phase diagrams for which carbon (C) is the first named element in the binary pair. The diagrams are presented with element compositions in weight percent. The atomic percent compositions are given in a secondary scale. For each binary system, a table of crystallographic data is provided that includes the composition, Pearson symbol, space group, and prototype for each phase.

This article contains a table that lists the electrical conductivity and resistivity of selected metals, alloys, and materials at ambient temperature. These include aluminum and aluminum alloys; copper and copper alloys; electrical heating alloys; instrument and control alloys; relay steels and alloys; thermostat metals; electrical contact materials; and magnetically soft materials.

Hardfacing is defined as the application of a wear-resistant material, in depth, to the vulnerable surfaces of a component by a weld overlay or thermal spray process Hardfacing materials include a wide variety of alloys, carbides, and combinations of these materials. Iron-base hardfacing alloys can be divided into pearlitic steels, austenitic (manganese) steels, martensitic steels, high-alloy irons, and austenitic stainless steel. The types of nonferrous hardfacing alloys include cobalt-base/carbide-type alloys, laves phase alloys, nickel-base/boride-type alloys, and bronze type alloys. Hardfacing applications for wear control vary widely, ranging from very severe abrasive wear service, such as rock crushing and pulverizing to applications to minimize metal-to-metal wear. This article discusses the types of hardfacing alloys, namely iron-base alloys, nonferrous alloys, and tungsten carbides, and their applications and advantages.

This article is a comprehensive collection of tables that list the nominal chemical composition of common powder metallurgy (PM) high-alloy tool steels, namely, PM high-speed, cold working, and corrosion-resistant tool steels.

The microstructure in the longitudinal direction of conventional high-alloy tool steels (HATS) depends very much on the degree of hot working. Comparing different processes, the highest processing temperature proves to be decisive for coarseness of the microstructure. This article provides a discussion on the microstructure of conventional HATS and hot isostatically pressed high-speed steel. The effects of the processing in cold worked HATS are illustrated.

This article focuses on the tribological behavior of group 1, 2, and 3 cobalt-base alloys, namely, carbide-type wear-resistant alloys and laves-type wear-resistant alloys. The behavior includes hardness, yield strength and ductility, and fracture toughness. The article contains a table that lists the nominal compositions and typical applications of cobalt-base alloys. It discusses the properties and relative performance of specific alloys when subjected to the more common types of wear. These include abrasive wear, high-temperature sliding wear, rolling-contact fatigue wear, and erosive wear.

Metallography plays a significant role in the quality control of metals and alloys used in the manufacture of implantable surgical devices. This article provides information and data on metallographic techniques along with images showing the microstructure of biomedical orthopedic alloys, including stainless steels, cobalt-base alloys, titanium and titanium alloys, porous coatings, and emerging materials.

This article discusses the physical metallurgy of cast cobalt alloys with an emphasis on the crystallography, compositions, phases and microstructure, and properties. Cobalt alloys are cast by several different foundry methods. The article describes the argon-oxygen decarburization and continuous casting process. It provides information on castability and quality of the casted alloys. The article details the postcasting treatment, including heat treatment, hot isostatic pressing, and coatings. It summarizes the applications of cast cobalt alloys.

Low-expansion alloys are characterized by their dimensional stability, suiting them for applications such as geodetic tape, bimetal strip, glass-to-metal seals, and electronic components. This article describes the composition of such alloys along with related properties and behaviors. It explains how humidity and other factors, such as heat treating and cold drawing, influence thermal expansion rates. It also provides machining information on some of the more common low-expansion alloys, and reviews special alloy types including iron-cobalt-chromium alloys, hardenable alloys, and high-strength controlled-expansion alloys.

Powder metallurgy (PM) high-alloy tool steels (HATS) have unique properties that assist them in solving various problems related to machining of metal components. This article describes the cost-intensive PM processing routes of HATS, as well as their major properties, including elastic properties, density, mechanical properties, grindability, fatigue and wear resistance, and thermophysical properties.

This article discusses the methods and procedures used to extract, purify, and synthesize tungsten carbide powder, metal, and other refractory carbide/nitride powders used in hard metal production. Selection of powders, additives, equipment, and processes for making ready-to-press hard metal powders is also discussed. The article also provides information on the emerging technologies for tungsten carbide synthesis and binders in hard metal production, such as cobalt, iron, and nickel.

Cemented carbide is, in its simplest form, a metal-matrix composite of tungsten carbide particles in a cobalt matrix. This article describes the microstructure, physical, and mechanical properties of cemented carbides. The properties discussed include thermal conductivity, magnetic properties, corrosion resistance, hardness, fracture toughness, wear resistance, and thermal shock resistance. The article concludes with information on the applications, grade classification, and selection of grades.