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.

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.

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.

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 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.

Liquid impingement erosion has been defined as progressive loss of original material from a solid surface due to continued exposure to impacts by liquid drops or jets. This article focuses on the core nature of erosion by liquid impingement, due to the greater appreciation of the distinctions between the different forms of erosion. It discusses steam turbine blade erosion, aircraft rain erosion, and rain erosion of wind turbine blades. The article describes the mechanisms of liquid impact erosion and time dependence of erosion rate. It reviews critical empirical observations regarding both impingement variables (velocity, impact angle, droplet size, and physical properties of liquids) and erosion resistance of materials, including the correlation between erosion resistance and mechanical properties and the effects of alloying elements and microstructure. The article also provides information on the ways to combat erosion.

Abrasive wear is a surface-damage process with material loss caused by hard asperities or abrasive particles occurring when two surfaces are sliding against each other. There are two types of abrasive wear: two-body abrasion and three-body abrasion. This article discusses the abrasive wear mechanism in ductile materials and commonly used testers for evaluating the resistance of materials to abrasive wear. The testers include pin-on-disk, block-on-ring, block-on-drum, and dry sand/rubber wheel abrasion tester. The article reviews the abrasion resistance of metallic materials, ceramic materials, and polymeric materials. It discusses factors that influence abrasive wear, including the environment, hardness, toughness, microstructure, and lubrication.

This article discusses the classification of wear based on the presence or absence of effective lubricants, namely, lubricated and nonlubricated wear. Variations in ambient temperature, atmosphere, load, and sliding speed, as well as variations in material bulk composition, microstructure, surface treatment, and surface finish of steel are also considered. The article discusses the types, wear testing, wear evaluation, and hardness evaluation of abrasive wear. It describes the selection criteria of steels for wear resistance. The article also describes the importance of hardness and microstructure as factors in resistance to wear. It provides a discussion on the resistance of various materials to wear in specific applications. The wear resistance of austenitic manganese steels is also discussed. The article discusses the applications of phosphate coatings, wear-resistant coatings, and ion implantation. It concludes with information on interaction of wear and corrosion.

This article reviews the factors influencing carburization to improve wear resistance of steel, such as operating temperature, cost, production volume, types of wear, and design criteria. It details the types of wear, namely abrasive wear and adhesive wear. The article discusses the characteristics of carburized steels that affect wear resistance, including hardness, microstructure, retained austenite, and carbides. It also describes the processing considerations for carburization of titanium.

Cemented carbides, best known for their superior wear resistance, have a range of industrial uses more diverse than that of any other powder metallurgy product including metalworking and mining tools and wear-resistant components. This article discusses raw materials and manufacturing methods used in the production of cemented carbides, the physical and mechanical properties of carbides, and wear mechanisms encountered in service. Emphasis is placed on tungsten carbide-cobalt (WC-Co) or tungsten carbide-nickel (WC-Ni) materials as used in nonmachining applications. Nominal composition and properties of representative cemented carbide grades and their applications are listed in a table.

Cast irons have been widely used by engineers in applications that require low cost, excellent castability, good damping capacity, ease of machining, and wear resistance. This article discusses the classification of wear for cast irons: adhesive wear, abrasive wear, and erosive wear. Typical wear applications for a variety of cast iron grades are listed in a table. The article reviews the general wear characteristics of gray irons, compacted graphite (CG) irons, and ductile irons. It discusses the typical compositions and properties of white and chilled iron castings. Gray cast iron is the dominant material for both brake drums and disk brake rotors. The article reviews brake lining chemistry effects, graphite morphology effects, and external abrasive effects on brake drums. It concludes with information on cast iron grinding balls.

Boronizing is a case hardening process for metals to improve the wear life and galling resistance of metal surfaces. Boronizing can be carried out using several techniques. This article discusses the powder pack cementation process for carrying out boronizing. It describes the structures of boride layers in ferrous materials and boride-layer structures in nickel-base superalloys. The primary reason for boriding metals is to increase wear resistance against abrasion and erosion. The article reviews the wear resistance and coefficient of friction of boride layers, as well as galling resistance of borided surfaces. It concludes with a discussion on boronizing plus physical vapor deposition (PVD) overlay coating.

Solid particle erosion (SPE) is the loss of material that results from repeated impact of solid particles energized in a carrier fluid. This article reviews important SPE variables, their effects for different classes of materials, composites and coatings, and the mechanisms and theories proposed to explain SPE. It discusses the SPE of metals, steels, and ceramics, as well as erosion of alloys with coarse, nominally two-phase microstructures in which the second-phase particles (SPPs) are typically large compared with the dimensions of the damage zone created by the impact of one particle. The article summarizes the erosion characteristics of polymer matrix composites (PMCs), metal matrix composites (MMCs), ceramic matrix composites (CMCs), and erosion-resistant coatings. The combination of parameters included in most erosion models is also summarized.

Austempered ductile iron (ADI) results from a specialty heat treatment of ductile cast iron. This article discusses the production of austempered ductile iron by heat treatment. The austempered ductile iron grades, according to ISO 17804 and EN 1564, are presented in a table. For economic reasons, or to avoid metallurgical problems, combinations of alloys are often used to achieve the desired hardenability in austempered ductile iron. The article provides information on the alloy combinations for austempered ductile iron. The mechanical properties, fracture toughness, fatigue, and abrasion resistance of the austempered ductile iron are discussed. The article concludes with information on the applications for austempered ductile iron.

The high-alloyed white irons are primarily used for abrasion-resistant applications and are readily cast into the parts needed in machinery for crushing, grinding, and handling of abrasive materials. This article discusses three major groups of the high-alloy white cast irons: nickel-chromium white irons, chromium-molybdenum irons, and high-chromium white irons. Mechanical properties for three white irons representing each of these three general groups are presented as bar graphs. The article also describes the various heat treatments of a martensitic microstructure, including austenitization, quenching, tempering, annealing, and stress relieving.

The high-alloy irons can be categorized into two main groups: the high-alloy graphitic irons (covering both gray and ductile grades) and the high-alloy white irons. High-alloy irons are used in applications with demanding requirements, such as high resistance to wear, heat, and corrosion, or for combined properties. This article discusses the specification and selection of high-alloy irons. The common alloying elements and their effect on the stable and metastable eutectic temperatures are listed in a table. The article provides information on the compositions, properties and applications of high-alloy graphitic irons and high-alloy white irons.

This article focuses on those areas of coatings technology where silicon-based technology (SBT) is the primary enabling technology and where SBT is used as an additive to provide unique properties to the coating film. It describes the chemistry and the uses of alkoxy silanes. The uses of silicates, siliconates, silicone fluids, and silicone resins in coatings are reviewed. The article discusses the various applications of SBT, namely, primers, heat-resistant coatings, industrial maintenance coatings, hygienic coatings, and abrasion-resistant coatings, and for marine biofouling control. It also provides information on the benefits of silicon-base additives.

Polyvinylidene fluoride (PVDF)-based coatings are typically used in outdoor applications that require exceptionally high performance and excellent long-term exterior durability with little maintenance. This article provides a background of three fluoropolymers most commonly used for coatings, namely, PVDF, polyvinyl fluoride, and polytetrafluoroethylene. It focuses on general properties, polymerization, resin types, coating formulation, technology of organic coatings, coating properties, and health and related safety considerations of PVDF. The article describes the application and typical end uses of PVDF-based coatings and the opportunities for improvement in PVDF-based coatings as with all organic coatings.

Polymeric floor coatings refer to flooring materials composed of multicomponent thermoset resins formulated with various fillers and pigments that are installed in situ, usually over concrete substrates. Polymeric flooring systems, specified for all industrial and commercial environments, use a variety of polymer chemistries and are constructed in a variety of methods and designs. This article provides a description of the service conditions for the polymeric flooring systems. It provides information on polymeric flooring systems, including thin-film coatings, self-leveling systems, membrane systems, broadcast systems, troweled systems, and terrazzo. The article also focuses on properties, applications, testing, and factors and requirements to be considered during the installation of polymeric floor coatings. It concludes with a discussion about coating failures, including bonding, cracking, chemical attack, and moisture that affect the polymeric floor coatings on concrete.