The high-carbon, high-chromium tool steels, designated as group D steels in the AISI classification system, are the most highly alloyed cold-work steels. This chapter describes the microstructures and hardenability of high-carbon, high-chromium tool steels and discusses the processes involved in the hardening and tempering of tool steels. It also covers the selection criteria and applications of high-carbon, high-chromium tool steels.

Tool steels represent a small, but very important, segment of the total production of steel. Their principal use is for tools and dies that are used in the manufacture of commodities. For the most part, the processes used for heat treating carbon and alloy steels are also used for heat treating tool steels, that is, annealing, austenitizing, tempering, and so forth. This chapter focuses on these heat treating processes of tool steels. Classification and approximate compositions and heating treating practices of some principal types of tool steels are provided. The steel types discussed include water-hardening; shock-resisting; oil-hardening cold-work; air-hardening, medium-alloy cold-work; high-carbon, high-chromium cold-work; low-alloy, special-purpose; mold; hot-work; and high-speed tool steels.

The several specific grades or compositions of tool steels have evolved over time and have been organized into useful groupings. This chapter presents the AISI classification system for tool steels, which categorizes tool steels by their alloying, applications, or heat treatment, and briefly describes the characteristics of each major group. It discusses selection criteria for tool steels, along with examples.

This article provides an overview of tool steels, discussing their composition, properties, and behaviors. It covers all types and classes of wrought and powder metal tool steels, including high-speed steels, hot and cold-work steels, shock-resisting steels, and mold steels. It explains how the properties of these steels are determined by alloying elements, such as tungsten, molybdenum, vanadium, manganese, and chromium, and the presence of alloy carbides. It describes the types of carbides that form and how they contribute to wear resistance, toughness, high-temperature strength, and other properties.

Tool steels are specialty steels, produced in relatively low volumes, optimized for applications requiring precise combinations of wear resistance, toughness, and hot hardness. This chapter describes the AISI classification system by which tool steels are defined. It discusses primary types, including high-speed and shock-resisting steels, and their associated subtype groups (W, L, S, O, A, D, H, M, and T series). It also discusses the types of carbides found in tool steels and their influence on mechanical properties. The chapter concludes with a discussion on heat treatment effects unique to tool steels, including two-phase effects, austenite stabilization, and the conditioning of retained austenite.

This chapter covers the friction and wear behaviors of carbon, alloy, and tool steels. It begins a review of commercially available shapes and forms. It then describes the metallurgy and microstructure of various designations and grades of each type of steel and explains how it affects their performance in adhesive and abrasive wear applications and in environments where they are subjected to solid particle, droplet, slurry, and cavitation erosion and fretting damage.

Tool steels are a special class of alloys designed for tool and die applications. High-speed steels are a subset of tool steels designed to operate at high speeds. This chapter describes the composition, properties, heat treatment, and use of wrought and alloyed tool steels, high-speed steels, and their counterparts made by powder metallurgy. It includes information on the chemical composition and application range of many commercial tool steels and explains how to apply coatings that reduce friction, thermal conductivity, and wear.

Tools steels are defined by their wear resistance, hardness, and durability which, in large part, is achieve by the presence of carbide-forming alloys such as chromium, molybdenum, tungsten, and vanadium. This chapter describes the alloying principles employed in various tool steels, including high-speed, water-hardening, shock-resistant, and hot and cold work tool steels. It discusses the influence of alloy design on the evolution of microstructure and properties during solidification, heat treating, and hardening operations. It also describes critical phase transformations and the effects of partitioning, precipitation, segregation, and retained austenite.

This chapter discusses the factors that affect die steel selection for hot forging, including material properties such as hardenability, heat and wear resistance, toughness, and resistance to plastic deformation and mechanical fatigue. It then describes the relative merits of various materials and the basic requirements for cold forging dies. The chapter also covers die manufacturing processes, such as high-speed and hard machining, electrodischarge machining, and hobbing, and the use of surface treatments.

This chapter focuses on the failure aspects of tool steels. The discussion covers the classification, chemical composition, main characteristics, and several failures of tool steels and their relation to heat treatment. The tool steels covered are hot work, cold work, plastic mold, and high-speed tool steels.

This chapter describes the various phases that form in tool steels, starting from the base of the Fe-C system to the effects of the major alloying elements. The emphasis is on the phases themselves: their chemical compositions, crystal structures, and properties. The chapter also provides general considerations of phases and phase diagrams and the determination of equilibrium phase diagrams. It describes the formation of martensite, characteristics of alloy carbides, and the design of tool steels.

There is a fairly wide variety of different tool steels for different applications. The American Iron and Steel Institute (AISI) classification of tool steels includes seven major categories: water-hardening tool steels, shock-resisting tool steels, cold work tool steels, hot work tool steels, low-alloy special-purpose tool steels, mold tool steels, high-speed tool steels, and powder metallurgy tool steels. This chapter provides discusses the manufacturing process, composition, properties, types, and applications of these tool steels and other cutting tool materials, such as cemented carbides. It also describes the methods of applying coatings to cutting tools to improve tool life.

The possible classification for tool steels is their division into four groups according to their final application: hot-worked, cold-worked, plastic mold, and high-speed tool steels. This chapter mainly follows such division by application, but the grade nomenclatures used here are primarily from AISI. It presents the classification of tool steels and discusses the principles and processes of tool steel heat treating, namely normalizing, annealing, hardening, and tempering. Various factors associated with distortion in several tool steels are also covered. The chapter discusses the composition, classification, and properties of unalloyed and low-alloy cold-worked tool steels; medium and high-alloy cold-worked tool steels; and 18% nickel maraging steels.

This chapter provides practical information on surface treatments that work by altering the surface chemistry of metals and alloys. It discusses the use of phosphate and chromate conversion coatings as well as anodizing, steam oxidation, diffusion coatings, and pack cementation. The chapter also covers ion implantation and laser alloying.

This chapter discusses the types of failures that can occur in sheet metal forming tools and explains how to mitigate their effects. It describes the factors that influence galling and wear and the benefits of special treatments and coatings. It provides information on through hardening, case (surface) hardening, and nitriding as well as hard chrome plating, vapor deposition, and thermal diffusion coating. It explains how to measure wear resistance using various tests and provides guidelines for selecting tool materials, treatments, and coatings.

Surface modification technologies improve the performance of tool steels. This chapter discusses the processes involved in oxide coatings, nitriding, ion implantation, chemical and physical vapor deposition processing, salt bath coating, laser and electron beam surface modification, and boride coatings that improve the performance of hot-work and high-speed tool steels.

This chapter presents an overview of some of the major causes of tool and die failures. The chapter describes fracture and fracture toughness of tool steels, and the influence of factors such as steel quality and primary processing, mechanical design, heat treatment, grinding and finishing, and distortion and dimensional change.

Mold steels are used for plastic molding and certain die-casting applications and are designated as group P steels in the AISI classification system. The fabrication and performance requirements that differentiate them from other types of tool steels are described in this chapter. It provides information on hubbing and machined cavity grades of mold steels and describes the performance of the corrosion-resistant mold steels. The chapter discusses the processes involved in forging, annealing, stress relieving, carburizing, hardening, and tempering of mold steels. It presents the selection criteria and applications of mold steels.

This article discusses the applications, compositions, and properties of cemented carbides and cermets. It explains how alloying elements, grain size, and binder content influence the properties and behaviors of cemented carbides. It also discusses the properties of steel-bonded carbides, or cermets, the various grades available, and the types of applications for which they are suited.

This chapter first lists the compositions of typical steels that are suitable for nitriding. It then presents considerations for steel selection. The chapter also shows the influence of alloying elements on hardness after nitriding and the depth of nitriding. It provides a detailed discussion on plasma nitriding of type 422 stainless steel, nitriding of type 440A and type 630 (17-4 PH) stainless steel. The chapter also discusses plasma nitride case depths.