The fluidized bed provides a means for exchanging heat between a metal part, the solid particles, and the fluidizing gas and which is viable for quenching. This article briefly considers the design aspects of the gas distributor, plenum, container, immersed cooling tubes and surface air spray cooling system in the quenching fluidized bed. It describes the fundamental factors affecting quenching power of the fluidized beds, namely, particle size, particle material, fluidizing gas composition, fluidizing gas flow rate, bed temperature and pressure, and the arrangement of quenched parts with respect to one another and to the bed. The article discusses the advantages, disadvantages, various applications and processes, including conventional batch quenching, two-step batch quenching, and continuous quenching of fluidized bed quenching, in detail.

This article discusses the important characteristics of fluidized beds. The total space occupied by a fluidized bed can be divided into three zones: grid zone, main zone, and above-bed zone. The article discusses the various types of atmospheres of fluidized beds, such as oxidizing and decarburizing atmosphere; nitrocarburizing and nitriding atmosphere; carburizing and carbonitriding atmosphere; and chemical vapor deposition atmosphere. External resistance heating, external combustion heating, internal resistance heating, direct resistance heating, submerged combustion heating, and internal combustion heating can be used to achieve the heat input for a fluidized bed. The article also describes the operations, design considerations, and applications of fluidized-bed furnaces in heat treating. Thermochemical surface treatments, such as carburizing, carbonitriding, nitriding, and nitrocarburizing, are also discussed. Finally, the article reviews the principles and applications of fluidized-bed heat treatment.

This article provides a detailed discussion on the heating equipment used for austenitizing, quenching, and tempering tool steels. These include salt bath furnaces, controlled atmosphere furnaces, fluidized-bed furnaces, and vacuum furnaces. The article discusses the types of nitriding and nitrocarburizing processes and the equipment required for heat treating tool steels to improve hardness, wear resistance, and thermal fatigue. The various nitriding and nitrocarburizing processes covered are salt bath nitrocarburizing, gas nitriding and nitrocarburizing, and plasma nitriding and nitrocarburizing.

Batch furnaces and continuous furnaces are commonly used in heat treating. This article provides a detailed account of various heat treating equipment and its furnace types, including salt bath equipment (externally heated, immersed-electrode and submerged-electrode furnaces), and fluidized-bed equipment (external-resistance-heated fluidized beds). It describes various auxiliary equipment used in cold-wall furnaces, namely, heating elements and pumping systems. Five types of heat-resistant alloys are used for furnace parts, trays, and fixtures: Fe-Cr alloys, Fe-Cr-Ni alloys, Fe-Ni-Cr alloys, nickel-base alloys and cobalt-base alloys. The article lists the recommended applications for alloys for parts and fixtures for various types of heat treating furnaces.

This article provides an overview of heat treatment processes, namely, solution heat treatment, quenching, natural aging, and artificial aging. It contains a table that lists the various heat treatment tempers commonly practiced for nonferrous castings. The article describes microstructural changes that occur due to the heat treatment of cast alloys.

The fundamental objective of quenching is to preserve, as nearly as possible, a metastable solid solution formed at the solution heat treating temperature, by rapidly cooling to some lower temperature, usually near room temperature. This article provides an overview of the factors used to determine a suitable cooling rate and the appropriate quenching process to develop a suitable cooling rate. It discusses the three distinct stages of quenching: vapor stage, boiling stage, and convection stage. The article reviews the factors that affect the rate of cooling in production operations. It discusses the quenchants that are used in quenching aluminum alloys, namely, hot or cold water and polyalkylene glycol. The article also describes the racking practices for controlling distortion and the level of residual stresses induced during the quench.

The thermoreactive deposition and diffusion process is a heat-treatment-based method to form coatings with compacted layers of carbides, nitrides, or carbonitrides, onto some carbon/nitrogen-containing materials, including steels. The amount of active carbide forming elements/nitride forming elements, coating temperatures and time, and thickness of substrates influence the growth rate of coatings. This article lists carbide and nitride coatings that are formed on carbon/nitrogen-containing metallic materials, and describes the coating process and mechanism of coating reagents. It details the growth process and nucleation process of carbide and nitride coatings formed on the metal surface. The article discusses the advantages, disadvantages, and characteristics of the various coating processes, including high-temperature salt bath carbide coating, high-temperature fluidized-bed carbide coating, and low-temperature salt bath nitride coating.

Quenching refers to the rapid cooling of metal from the solution treating temperature, typically between 465 and 565 deg C (870 and 1050 deg F) for aluminum alloys. This article provides an overview on the appropriate quenching process and factors used to determine suitable cooling rate. It describes the quench sensitivity and severity of alloys, quench mechanisms and the different types of quenchants used in immersion, spray, and fog quenching. The article provides a detailed description of the quench-factor analysis that mainly includes residual stress and distortion, which can be controlled by proper racking. It concludes with information on agitation and the quench tank system used in the quenching of aluminum alloys.

Furnaces are one of the most versatile types of industrial appliances that span many different areas of use. This article discusses the classification of various furnaces used in heat treating based on the mode of operation (batch-type furnaces and continuous-type furnaces), application, heating method, mode of heat transfer, type of materials handling system, and mode of waste heat recovery (recuperation and regeneration). It provides information on uniform temperature distribution, the general requirements and selection criteria for insulation materials, as well as the basic safety requirements of these furnaces.

Functional fusion-bonded epoxy (FBE) coatings are used as external pipe coatings, base layer for three-layer pipe-coating systems, internal pipe linings, and corrosion coatings for concrete reinforcing steel (rebar). This article provides information on the chemistries of FBE, and discusses the application procedures for internal and external FBE pipe coating. The procedures involve pipe inspection, surface preparation, heating, powder application, curing, cooling, coating inspection, and repairing. It describes the problems and solutions for FBE external pipe coatings, girth weld FBE application, FBE custom coatings, internal FBE pipe linings, and FBE rebar coatings.