This article presents the mechanisms of polymer wear and quantifies wear in terms of wear rate (rate of removal of the material). Interfacial and bulk wear are discussed as well as a discussion on the wear study of "elastomers," "thermosets," "glassy thermoplastics," and "semicrystalline thermoplastics." The article also discusses the effects of environment and lubricant on the wear failures of polymers. It presents a case study on considering nylon as a tribological material and failure examples, explaining wear resistance of polyurethane elastomeric coatings and failure of an acetal gear wheel.

Tribology is the study of contacting materials in relative motion and more specifically the study of friction, wear, and lubrication. This article discusses the classification and the mechanisms of friction, wear, and lubrication of polymers. It describes the tribological applications of polymers and the tribometers and instrumentation used to measure the tribological properties of polymers. The article discusses the processes involved in calculating the wear rate of polymers and the methods of characterization of the sliding interface. It provides information on the pressure and velocity limit of polymer composites and polymer testing best practices.

Reinforced polymers (RPs) are widely used in structural, industrial, automotive, and engineering applications due to their ecofriendly nature and the potential to manipulate their properties. This article addresses the technical synthesis of RPs, referring to their tribological behavior, to provide insights into the contribution and interaction of influential parameters on the wear behavior of polymers. It provides a brief discussion on the effects of significant parameters on RP tribology. The article describes abrasive and adhesive wear and provides a theoretical synthesis of the literature regarding the wear mechanisms of RPs. It also describes the synthesis of abrasive wear failure of different types of RPs and highlights the contribution of these influential parameters. The article addresses the synthesis of adhesive wear failure of different types of RPs.

Impact or percussive wear is defined as the wear of a solid surface that is due to percussion, which is a repetitive exposure to dynamic contact by another body. Impact wear, however, has many analogies to the field of erosive wear. The main difference is that, in impact wear situations, the bodies tend to be large and contact in a well-defined location in a controlled way, unlike erosion where the eroding particles are small and interact randomly with the target surface. This article describes some generic features and modes of impact wear of metals, ceramics, and polymers. It discusses the processes involved in testing and modeling of impact wear, and includes two case studies.

Friction and wear are important when considering the operation and efficiency of components and mechanical systems. Among the different types and mechanisms of wear, adhesive wear is very serious. Adhesion results in a high coefficient of friction as well as in serious damage to the contacting surfaces. In extreme cases, it may lead to complete prevention of sliding; as such, adhesive wear represents one of the fundamental causes of failure for most metal sliding contacts, accounting for approximately 70% of typical component failures. This article discusses the mechanism and failure modes of adhesive wear including scoring, scuffing, seizure, and galling, and describes the processes involved in classic laboratory-type and standardized tests for the evaluation of adhesive wear. It includes information on standardized galling tests, twist compression, slider-on-flat-surface, load-scanning, and scratch tests. After a discussion on gear scuffing, information on the material-dependent adhesive wear and factors preventing adhesive wear is provided.

Wrought 4xxx alloys (extrusions and forgings) exhibit high surface hardness, wear resistance, and a low coefficient of thermal expansion. This article provides a summary of brazing filler metals used to join brazeable aluminum-base metals. It contains tables that list the nominal composition and filler-metal alloys of 4xxx series used in structural forms.

The aluminum alloy 336.0 is a high-silicon alloy suitable for applications where good high-temperature strength, low coefficient of thermal expansion, and good resistance to wear are required. This datasheet provides information on key alloy metallurgy, processing effects on physical and mechanical properties, fabrication characteristics, and application characteristics of this 3xxx series alloy.

Aluminum alloys are widely used in engineered components because of their excellent strength-to-weight ratio. Their use in applications requiring wear resistance is more limited. One of the main limitations of aluminum alloys is the poor tribological behavior mainly due to their relatively low hardness, which favors large plastic deformation under sliding conditions. This article discusses the classes and mechanisms of wear in aluminum-silicon alloys, aluminum-tin bearing alloys, and aluminum-matrix composites; describes the effect of material-related parameters on wear behavior of these alloys; and reviews their applications in a variety of tribological applications in the automotive industry ranging from aluminum-tin alloys for plain bearings to alloys with hard anodizing for machine elements. Methods to improve wear resistance and alloy hardness are also discussed.

This article provides a summary of the concepts discussed in the articles under the Section “Introduction and Basic Theory of Wear” in ASM Handbook, Volume 18, Friction, Lubrication, and Wear Technology .

This article describes two variations of carbon-base coatings: diamondlike carbon (DLC) coatings and polycrystalline diamond (PCD) coatings. It discusses the basics of a few deposition methods as they apply to industrially relevant coatings. The methods include deposition of tungsten-containing hydrogenated amorphous carbon films, deposition of tetrahedral amorphous carbon films, and deposition of silicon-incorporated hydrogenated amorphous carbon films. The most common deposition technologies for diamond films are also discussed. The article provides information on surface preparation for DLC and diamond deposition. It also provides a discussion on the coating composition and structure, mechanical and tribological properties, and applications of DLC and diamond coatings. The quality control techniques for DLC and diamond coatings are specified to meet customer requirements and ensure repeatable quality.

This article describes friction force as a function of normal force in dry forming. It focuses on metal forming operations usually classified as cold working and hot working based on metallurgical considerations. The article discusses surface flattening and roughening of workpiece asperities in metal forming. It presents advanced tribology models and results for friction in isothermal forging operations in which the tooling is maintained at a temperature close to that of the workpiece. The article provides information on heat transfer models. It discusses the effect of wear in manufacturing processes. The article concludes with information on the main categories of tool and die materials used for a variety of manufacturing application.

Stainless steels are characterized as having relatively poor wear resistance and tribological properties, but they are often required for a particular application because of their corrosion resistance. This article describes the classification of stainless steels and wear. Stainless steels have been classified by microstructure and are categorized as austenitic, martensitic, ferritic, or duplex. The main categories of wear are related to abrasion, erosion, adhesive wear, and surface fatigue. The article presents a list that proposes the alloy family that could be the optimal selection for a particular wear mode. The corrosion modes include dry sliding, tribocorrosion, erosion, erosion-corrosion, cavitation, dry erosion, erosion-oxidation, galling and fretting.

Impact wear can be defined as the wear of a solid surface that is due to percussion, which is a repetitive exposure to dynamic contact by another solid body. This article discusses the volume (or mass) removal of material either at or under engineering contact stress levels and outlines a rational, semi-empirical impact wear theory. It illustrates a linear wear mechanism that occurs in print heads and repetitive impacts that take place in metallic machine contacts. The article concludes with information on plotting a wear curve for an originally plane, massive carbon steel machine platen subjected to repetitive compound impact by a hard, nonwearing spherical-ended steel alloy component.

Seals are mechanical components that prevent the leakage, diffusion, transfer, or mixing of different liquid, gas, solid, and multiphasic substances. This article begins by discussing the classifications of seals: static and dynamic. Static seals involve both self-energizing elastomeric materials such as O-rings, which merely react to a sealed fluid pressure, and passive materials that require clamping forces to achieve sealing, such as gaskets. The types of dynamic seals include rotary seals and reciprocating seals. The article describes the factors affecting seal wear and failure. It provides a list of some common seal wear modes and failures, namely abrasion, cavitation damage, chemical attack, compression set, corrosion, damage during abrupt decompression, dieseling damage, extrusion damage, installation damage, spiral or rolling damage, and vaporization damage. The article concludes with specific recommendations for reducting of seal friction and wear.

This article is concerned with gear tooth failures influenced by friction, lubrication, and wear, and especially those failure modes that occur in wind-turbine components. It provides a detailed discussion on wear (including adhesion, abrasion, polishing, fretting, and electrical discharge), scuffing, and Hertzian fatigue (including macropitting and micropitting). Details for obtaining high lubricant specific film thickness are presented. The article describes the selection criteria for lubricants, such as oil, grease, adhesive open gear lubricant, and solid lubricants. It discusses the applications of oil and gear lubricants and the types of standardized gear tests. The article presents some recommendations for selecting lubricants and lubricant viscosity for enclosed gear. It provides some examples of failure modes that commonly occur on gears and bearings in wind turbine gearboxes.

This article describes the numerous techniques used to measure friction. It provides a brief description of the historical development of friction testing. The article discusses the tests and equipment available for friction testing. It explains the procedural considerations that should be addressed to ensure that valid data are derived from a friction test. The article presents definitions of terms commonly used in tribology such as static friction, kinetic coefficient of friction, stick-slip behavior, and lubricated friction. It provides information on the precautions that must be taken to ensure valid test results. The article also describes how to report data and how to analyze these data.

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.

This article introduces the structure, tribological properties, advantages, and applications of ionic liquids (ILs) as lubricating media. It discusses the mechanisms of IL lubrication for different contacts. The advances in studies focusing on tribological properties of a wide range of ILs are reviewed. The article concludes with the challenges that limit the applications of ILs in tribology engineering.

This article describes the characteristics of three types of gas bearings, such as aerostatic bearing, precision aerodynamic bearing (PAB), and compliant aerodynamic bearing (CAB). It discusses the applications for aerostatic bearings and advantages in lubricating a bearing with a compressible gas. The article also describes the different types of aerostatic bearings, such as annular thrust bearings and orifice-compensated journal bearings. It presents a discussion on load capacity and stiffness, friction and power loss, and stability and damping of the aerostatic bearings. The article provides a discussion on the types of PAB and CAB. The types include spiral groove annular thrust bearings, cylindrical journal bearings, three-sector journal bearings, tilting-pad journal bearings, and helical-grooved journal bearings. The types of CAB include foil bearings and pressurized-membrane bearings. The article concludes with a description of factors that influence materials selection for gas-lubricated bearings.

This article discusses the importance of friction and wear and the role of lubricants in composites. It highlights the progress and developments in using different forms of carbon allotropes in composites for improved friction and wear performance of materials. The article focuses on the widely used form known as carbon black (CB) and shows how to deal with friction and wear of polymers and composites when gamma irradiation is involved. It also discusses the role of graphite in composite materials, which is widely used as a dry lubricant. The article examines the tribology of carbon nanotubes (CNTs) as components in composite materials. It also highlights some of the most pronounced examples of graphene use as a reinforcement agent for improving tribological performance in composite matrices. The article concludes with a discussion on the progress of research in diamond-containing composites.