This article focuses on various vacuum heat treating processes for additively manufactured parts, namely annealing and stress relieving, solid-solution annealing, and solution treating and aging. It addresses several practical concerns involved in using vacuum heat treatment, including temperature measurement, unvented cavities, loose powder, and direct contact of metals in the high-temperature vacuum. The article provides a short discussion on sintering and evaporation of metals in vacuum furnaces.

Gray irons are a group of cast irons that form flake graphite during solidification, in contrast to the spheroidal graphite morphology of ductile irons. This article describes surface hardening of gray irons by flame and induction heating. It provides information on the classification of the gray irons in ASTM specification. The article presents examples that illustrate the use of stress relieving to eliminate distortion and cracking. It describes the three annealing treatments of gray iron: ferritizing annealing, medium (or full) annealing, and graphitizing annealing. The article discusses the parameters of the tensile strength and hardness of a normalized gray iron casting. These include combined carbon content, pearlite spacing, and graphite morphology. The article concludes with a discussion on the induction hardening of gray iron castings.

Cast irons, like steels, are iron-carbon alloys but with higher carbon levels than steels to take advantage of eutectic solidification in the binary iron-carbon system. This article introduces the solid-state heat treatment of iron castings and describes the various processes of heat treatment of cast iron. It provides information on stress relieving, annealing, normalizing, through hardening, and surface hardening of these castings. The article discusses general considerations for the heat treatment of cast iron. Cast irons are occasionally nitrided for various applications with the aim of enhancing surface hardness and corrosion resistance of the products. The article describes molten salt bath cyaniding and ion nitriding of cast iron.

Ductile cast irons are heat treated primarily to create matrix microstructures and associated mechanical properties not readily obtained in the as-cast condition. This article discusses the most important heat treatments of ductile irons and their purposes. International standards of ductile iron provided by ASTM International, the International Organization for Standardization (ISO), and SAE International are presented in a table. The article explains basic structural differences between the ferritic, pearlitic, martensitic, and ausferritic classes. It presents recommended practices for annealing ductile iron castings for different alloy contents and for castings with and without eutectic carbides. The article discusses the induction surface hardening and remelt hardening of ductile iron. It concludes with information on the effect of heat treatment on fatigue strength of ductile iron.

This article describes the heat treatment of wrought solid-solution and precipitation-hardening alloys with a focus on the major families of wrought nickel alloys. It also provides information on the heat treatment of some representative solid-solution alloys in the Monel (Ni-Cu), Inconel (Ni-Cr-Mo), Hastelloy (Ni-Mo-Cr), and Incoloy (Ni-Fe-Cr) families of alloys. The heat treatment processes for gamma prime nickel alloys, gamma prime nickel-iron superalloys, and gamma double-prime nickel-iron superalloys are also included. The article also provides information on age-hardenable alloys, and the effects of cold work on aging response and grain growth with examples.

Brasses are copper alloys with zinc as the principal alloying element. This article provides information on the chemical compositions and mechanical properties of the three types of brasses: alpha, duplex and beta. It briefly discusses the Unified Numbering System designations, compositions, and classifications of wrought brasses and cast brasses. The article provides a discussion on annealing, recrystallization, and grain growth of wrought brasses. Stress relief of wrought brasses, which is typically conducted below the annealing temperatures, is also briefly described.

This article provides information on nickel alloying elements, and the heat treatment processes of various nickel alloys for applications requiring corrosion resistance and/or high-temperature strength. These processes are homogenization, annealing, solution annealing, solution treating, stabilization treatment, age hardening, stress relieving, and stress equalizing. Discussion of furnaces, fixtures, and atmospheres is included. Nickel alloys used for the heat treatment processes include corrosion-resistant nickel alloys, heat-resistant nickel alloys, nickel-beryllium alloys, special-purpose alloys such as nitinol shape memory alloys, low-expansion alloys, electrical-resistance alloys and soft magnetic alloys. Finally, the article focuses on heat treatment modeling for selecting the appropriate heat treatment process.

This article provides information on the Unified Numbering System designations and temper designations of copper and copper alloys. It discusses the basic types of heat treating processes of copper and copper alloys, namely, homogenizing, annealing, and stress relieving, and hardening treatments such as precipitation hardening, spinodal hardening, order hardening, and quench hardening and tempering. The article presents tables that list the compositions and mechanical properties of copper alloys. It also discusses two strengthening mechanisms of copper alloys, solid-solution strengthening and work hardening. Finally, the article provides information on the equipment used for the heat treating of copper and copper alloys, including batch-type atmosphere furnaces, continuous atmosphere furnaces, and salt baths.

This article provides a detailed discussion on heat treatment of titanium alloys such as alpha alloys, alpha-beta alloys, and beta and near-beta alloys. Common processes include stress-relief, annealing, solution treating, aging, quenching, and age hardening. It provides information on the effects of alloying elements on alpha/beta transformation. The article also discusses the heat treating procedures, and the furnaces used for heat treating titanium and titanium alloys.

Gray irons are a group of cast irons that form flake graphite during solidification, in contrast to the spheroidal graphite morphology of ductile irons. The heat treatment of gray irons can considerably alter the matrix microstructure with little or no effect on the size and shape of the graphite achieved during casting. This article provides a detailed account of classes of gray iron, and heat treating methods of gray irons with examples. These methods include stress relieving, annealing, normalizing, transformation hardening, austenitizing, quenching, austempering, martempering, flame hardening, induction hardening, and nitriding.

This article introduces the general principles and applications of heat treatment to iron castings. It provides a detailed discussion on the heat treatment processes, namely, stress relieving, annealing, normalizing, throughhardening, and surface hardening for various types of cast irons. These include gray iron, ductile iron, compacted graphite iron, white iron, malleable iron, and high-alloy iron. The article describes how to control temperature and atmosphere during the heat treatment of the iron castings.

Tool steels are an important class of steels due to their distinct applications and their specific heat treating issues. This article provides an overview of the classification and production of tool steels, and discusses the procedures and process control requirements for heat treating principal types of tool steels. It reviews the various heat treating processes, namely, normalizing, annealing, stress relieving, austenitizing, quenching, and tempering, and surface treatments and cold treating. The article also provides information on the applicability of these processes to various types of tool steels.

Ductile cast irons are heat treated to create matrix microstructures and associated mechanical properties not readily obtained in the as-cast condition. This article provides a detailed account of the general characteristics of ductile irons. It discusses the most important heat treatments of ductile irons, namely, stress relieving, austenitizing, annealing, normalizing, quenching, martempering, austempering, and surface hardening. The article elucidates the effects of these heat treatments on the mechanical properties of the ductile irons.

This article provides information on the metallurgy of austenitic stainless steels, and the formation of their intermediate phases (Sigma, Chi, and Laves). It discusses sensitization, a major problem associated with the austenitics, and solutions to avoid the problem. The article describes heat treatments applied to austenitic stainless steels, namely, soaking for homogenization and preparation for hot working; annealing to remove the effects of cold work and to put alloying elements into solid solution; and stress relieving. It provides information on the stabilizing anneal process, which is conducted on stabilized alloys, and discusses the metallurgical characteristics of austenitic stainless steels that may affect the selection of a stress-relieving treatment and prevention of stress corrosion by stress relieving. The article also discusses the heat treatments applied to duplex stainless steels, which involve soaking and annealing, achieving the austenite-ferrite balance, precipitation of intermetallics, and alpha prime precipitation.

Hardenable steels with high-alloy content includes a family of nickel-cobalt steels with high strength and high toughness. This article describes various heat treatments, namely, normalizing, annealing, hardening, tempering, stress relieving, overaging, quenching, refrigeration, and straightening treatment, applied to HP9-4-20, HP9-4-25, HP9-4-30, and HP9-4-45 steels. These steels have high fracture toughness when heat treated to very high strength levels. The article also describes heat treatments applied to other alloys such as AF 1410, AerMet 100, AerMet 310, and AerMet 340, which provide a good combination of high strength and toughness that make them attractive for aerospace application. It also presents tables that provide information on the effect of aging temperatures and heat treatment on mechanical properties and impact energy of these steels.

This article focuses on various heat treatment practices recommended for different types of high-speed tool steels. Commonly used methods include annealing, stress relieving, preheating, austenitizing, quenching, tempering, carburizing, and nitriding. The article describes hardening for various types of cutting tools, namely, broaches, chasers, milling cutters, drills, taps, reamers, form tools, and hobs, and for thread rolling dies, threading dies, and bearings.

This article provides a discussion on heat treating practices, namely, carburizing, normalizing, annealing, stress relieving, preheating, austenitizing, quenching, tempering, and nitriding for various grades of mold and corrosion-resistant tool steels. It details the characteristics of various grades of mold and corrosion-resistant tool steels, including type P20, type P20Mod, AISI type 420, and AISI type 440B.

Martensitic stainless steels are the least corrosion-resistant of all stainless alloys. The traditional martensitic stainless steels are iron/chromium/carbon alloys, sometimes with a small amount of nickel and/or molybdenum. This article provides an overview on the influences of the various possible alloying elements on the key properties of martensitic stainless steels. It describes the various preparation processes, namely, atmosphere selection, cleaning, and preheating, prior to heat treatment for these steels. Common heat treatment methods include annealing, hardening, tempering, and stress relieving. The article lists the compositions of casting alloys and also describes the effect of tempering temperature on the hardness, strength, ductility, and toughness properties of the alloys.

Induction heating has the ability to concentrate the electromagnetic field and heat within a certain area of the workpiece. This article provides a detailed discussion on the end heating of bars, rods, and billets using solenoid inductors, oval inductors, and channel inductors. It reviews the importance of computer modeling in predicting the impact of different, interrelated, and nonlinear factors on the transitional and final thermal conditions of billets and bars. The article describes the most appropriate processes to improve end heating process effectiveness. Induction bending of narrow circumferential band of pipe or tube is also discussed. The article concludes with a discussion on stress relieving of pipe ends and welded areas.

Cold treating of steel can be used to enhance the transformation of austenite to martensite and improve the stress relief of castings and machined parts. Cryogenic treatment of steel is a distinct process that uses extreme cold to modify the performance of materials. This article explains the practices employed and equipment used in the cold treatment of steel. It also presents the results of using cryogenic treatment to enhance steel properties.