Rolling-element bearings, also called rolling bearings and antifriction bearings, tend to have very low friction characteristics compared to plain bearings or simple sliding bearings. This article discusses the types of rolling-element bearings, namely, ball bearings and roller bearings. It provides information on the bearing component materials. The article describes the lubrication requirements and lubrication methods, namely, elastohydrodynamic lubrication and grease lubrication. It reviews the adjustment factors influencing fatigue life of the bearing. The article also provides information on bearing load ratings, standard bearing geometries, rolling bearing friction factors, and wear and its control methods. It concludes with a discussion on damage modes of bearings.

Plastics or polymers are used in a variety of engineering and nonengineering applications where they are subjected to surface damage and wear. This article discusses the classification of polymer wear mechanisms based on the methodologies of defining the types of wear. The first classification is based on the two-term model that divides wear mechanisms into interfacial and bulk or cohesive. The second is based on the perceived wear mechanism. The third classification is specific to polymers and draws the distinction based on mechanical properties of polymers. In this classification, wear study is separated as elastomers, thermosets, glassy thermoplastics, and semicrystalline thermoplastics. The article describes the effects of environment and lubricant on the wear failures of polymers. It presents a case study on nylon as a tribological material. The article explains the wear failure of an antifriction bearing, a nylon driving gear, and a polyoxymethylene gear wheel.

This article provides an overview of two major classes of bearings: rolling bearings and sliding, or plain, bearings. It reviews the experimental data resulted from testing of rolling and sliding bearing materials with illustration. The article presents a table that summarizes rolling contact fatigue test methods that ASTM published in STP 771. It also describes the role of lubrication in the bearings.

Magnetic field testing includes some widely used nondestructive evaluation methods to inspect magnetic materials for defects such as cracks, voids, and inclusions and to assess other material properties, such as grain size, texture, and hardness. This article discusses the principles of such defect detection, providing details on the origin, generation, and assessment of leakage field data. In addition, it discusses the metallurgical and magnetic properties of magnetic materials and the applications of magnetic field testing.

Rust-preventive compounds are removable coatings used for the protection of the surfaces of iron, steel, coated or galvanized products, and other alloys. This article describes the basic parts of rust-preventive compounds, namely, carrier, film former, polar materials, and specialty additives. It explains types of rust-preventive compounds, including dry films and water-based dry films. The article also discusses the methods of application of various compounds, such as petrolatum compounds and emulsion compounds. It contains tables that provide information on the characteristics, applications, and physical properties of rust-preventive materials covered by military specifications. Finally, the article describes the various considerations and parameters for selecting rust-preventive materials.

Wire rod is a semifinished product rolled from billet on a rod mill and is used primarily for the manufacture of wire. Steel wire rod is usually cold drawn into wire suitable for further drawing; for cold rolling, cold heading, cold upsetting, cold extrusion, or cold forging; or for hot forging. The article explains these operations, along with the several recognized quality and commodity classifications applicable to steel wire rods. The heat treatments commonly applied to steel wire rod, either before or during processing into wire, include annealing, spheroidize annealing, patenting, and controlled cooling. When the end product must be heat treated, the heat treatment and mechanical properties should be clearly defined. Carbon steel rods are produced in various grades or compositions: low-carbon, medium-low-carbon, medium-high-carbon, and high-carbon steel wire rods. Rod for the manufacture of carbon steel wire is produced with manufacturing controls and inspection procedures intended to ensure the degree of soundness and freedom from injurious surface imperfections necessary for specific applications. This article also describes the various quality descriptors applicable to the rods as well as standard qualities and commodities available in alloy steel wire rod.

A sliding bearing (plain bearing) is a machine element designed to transmit loads or reaction forces to a shaft that rotates relative to the bearing. This article explains the role of wear damage mechanisms in the design and selection of bearing materials, and its relationship with bearing material properties. Sliding bearings are commonly classified by terms that describe their application; they also are classified according to material construction, as single-metal, bimetal, or trimetal sliding bearings. The article further provides detailed tabular data on the designation and composition of the following types of bearing materials: tin-base alloys, lead-base alloys, copper-base alloys, and aluminum-base alloys. It also briefly discusses the following types of bearing materials: zinc-base alloys, silver-base alloys, gray cast irons, cemented carbides, and nonmetallic bearing materials.

Hot-rolled steel bars and other hot-rolled steel shapes are produced from ingots, blooms, or billets converted from ingots or from strand cast blooms or billets and comprise a variety of sizes and cross sections. Most carbon steel and alloy steel hot-rolled bars and shapes contain surface imperfections with varying degrees of severity. Seams, laps, and slivers are probably the most common defects in hot-rolled bars and shapes. Another condition that could be considered a surface defect is decarburization. Hot-rolled steel bars and shapes can be produced to chemical composition ranges or limits, mechanical property requirements, or both. Hot-rolled carbon steel bars are produced to two primary quality levels: merchant quality and special quality. Merchant quality is the least restrictive descriptor for hot-rolled carbon steel bars. Special quality bars are employed when end use, method of fabrication, or subsequent processing treatment requires characteristics not available in merchant quality bars.

The choice of heat treatment depends on the service requirements of a given bearing and how the bearing will be made. This article describes the design parameters, material characteristics required to sustain performance characteristics, metallurgical properties, and dimensional stability. It also provides a description of various extensively-used heat treatment processes, namely, carburizing, carbonitriding, induction surface hardening, and nitriding associated with various bearings. In addition, the article explores the factors to be considered in selecting a process and explains why it is optimum for a specific application.

Polymers and polymer composites have become attractive for tribological applications due to their specific material properties. This article begins by discussing the fundamentals of polymer friction and wear. It summarizes the main polymer materials used in tribological applications. The article explains the effects of load, sliding velocity, and temperature on the friction coefficient. It describes three types of wear modes, namely, abrasive, adhesion, and fatigue. The article discusses the frictional behavior of polymer composites and polymer coatings. It concludes by providing information on tribotesting of polymers and polymer composites.

A sliding bearing (plain bearing) is a machine element designed to transmit loads or reaction forces to a shaft that rotates relative to the bearing. This article discusses the properties of bearing materials. It provides information on bearing material systems: single-metal systems, bimetal systems, and trimetal systems. The article describes the designations, nominal compositions, mechanical properties, and applications of various sliding bearing alloys: tin-base alloys, lead-base alloys, copper-base alloys, aluminum-base alloys, silver-base alloys, zinc-base alloys, additional metallic materials, nonmetallic materials. It describes casting processes, powder metallurgy processes, and electroplating processes. The article also discusses the selection criteria for bearing materials.

High removal rate (HRR) machining involves the use of extremely rigid, high-power, high-precision machines, such as roll turning lathes, to achieve material removal rates far beyond the capacity of conventional machine tools. This article reviews the machine requirements and cutting parameters of HRR machining. Machine components such as the lathe bed, tailstock, headstock, carriage, and tooling are detailed. The article also discusses the applications of HRR machining.

Ring rolling is a process for creating seamless ring shaped components using specialized equipment and forming processes. This article provides information on the applications of ring rolling. It discusses the types of machines used for ring rolling, namely, vertical rolling machines, radial-axial horizontal rolling machines, four-mandrel mechanical table mills, three-mandrel table mills, and automatic radial-axial multiple-mandrel ring mills. The article provides a discussion on the process control technology and ancillary operations of ring rolling. It describes the methods of producing ring blanks and the various types of blanking and rolling tools used in ring rolling process. The article concludes with a discussion on rolled ring tolerances and machining allowances.

The mechanism of contact fatigue can be understood in terms of several sources of stress concentration, or stress raisers, within the macroscopic Hertzian stress field. This article focuses primarily on rolling contact fatigue of hardened bearing steels. It discusses Hertzian shear stresses at and below the contact surfaces and briefly summarizes bearings and gear characteristics. The article provides an overview of the key types of gear and bearing steels. It analyzes two types of macropitting that result from the subsurface growth of fatigue cracks, namely, subsurface-origin macropitting and surface-origin macropitting. The article describes the factors influencing contact fatigue life of hardened steel bearings and gears, including hardness, inclusions, carbides, and residual stresses.

This article focuses on the electrodeposition of indium and its alloys, such as indium-antimony, indium-gallium, and indium-bismuth, in nonaqueous indium plating baths. It also provides information on the stripping of indium plate from plated components and presents an overview of the specifications, standards, and hazards of indium plating.

Babbitting is a process by which relatively soft metals are bonded chemically or mechanically to a stronger shell or stiffener which supports the weight and torsion of a rotating, oscillating, or sliding shaft. This article focuses on workpiece preparation and babbitting methods. Prior to casting, the workpiece must be scrupulously prepared by various cleaning, fluxing, and tinning steps. Babbitting of bearing shells can be accomplished by three methods, namely, static babbitting, centrifugal casting, and metal spray babbitting.

Bearings are usually provided where a specific spatial relationship (alignment) must be maintained between the parts or where a force is to be transmitted from one part to the other. This article introduces the general types and configuration of sliding bearings, bearing materials, and the practical aspects and solutions in the friction, lubrication, and wear mitigation of sliding bearings. The lubrication of bearings includes thick-film lubrication, thin-film lubrication, and boundary lubrication. The article concludes with a discussion on the effects of material elasticity on the lubrication of bearings.

Rolling-element bearings use rolling elements interposed between two raceways, and relative motion is permitted by the rotation of these elements. This article presents an overview of bearing materials, bearing-load ratings, and an examination of failed bearings. Rolling-element bearings are designed on the principle of rolling contact rather than sliding contact; frictional effects, although low, are not negligible, and lubrication is essential. The article lists the typical characteristics and causes of several types of failures. It describes failure by wear, failure by fretting, failure by corrosion, failure by plastic flow, failure by rolling-contact fatigue, and failure by damage. The article discusses the effects of fabrication practices, heat treatment and hardness of bearing components, and lubrication of rolling-element bearings with a few examples.

This article reviews the general characteristics of fretting wear in mechanical components with an emphasis on steel. It focuses on the effects of physical variables and the environment on fretting wear. The variables include the amplitude of slip, normal load, frequency of vibration, type of contact and vibration, impact fretting, surface finish, and residual stresses. The form, composition, and role of the debris are briefly discussed. The article also describes the measurement, mechanism, and prevention of fretting wear. It concludes with several examples of failures related to fretting wear.