This article provides a qualitative summary of the theory of diffusion bonding, as distinguished from the mechanisms of other solid-state welding processes. Diffusion bonding can be achieved for materials with adherent surface oxides, but the resultant interface strengths of these materials are considerably less than that measured for the parent material. The article describes three stages of diffusion bonding: microasperity deformation, diffusion-controlled mass transport, and interface migration. It concludes with information on diffusion bonding with interface aids.

Diffusion bonding is only one of many solid-state joining processes wherein joining is accomplished without the need for a liquid interface (brazing) or the creation of a cast product via melting and resolidification. This article offers a qualitative summary of the theory of diffusion bonding. It discusses factors that affect the relative difficulty of diffusion bonding oxide-bearing surfaces. These include surface roughness prior to welding, mechanical properties of the oxide, relative hardness of the metal and its oxide film, and prestraining or work hardening of the material. The article describes the mechanism of diffusion bonding in terms of microasperity deformation, diffusion-controlled mass transport, and interface migration. It concludes with a discussion on diffusion bonding with interface aids.

Diffusion welding involves minimal pressurization, but relatively high temperatures and long periods of time. This article discusses the process variants of diffusion welding: solid-phase and liquid-phase processes. It describes the diffusion welding of carbon and low-alloy steels, high-strength steels, stainless steels, and aluminum-base alloys. The article provides a discussion on dissimilar metal combinations, such as ferrous-to-ferrous combinations, nonferrous-to-nonferrous combinations, ferrous-to-nonferrous combinations, and metal-ceramic joining.

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.

The influence of friction and wear on the function and structure of tribological systems is determined by various types of tribological tests. This article introduces the general categories of tribological testing and describes the basic objectives of testing. It reviews the results of tribological tests, where the system-dependent characteristics of friction and wear data can be expressed in different forms, such as tribographs, transition diagrams, and tribomaps. A summary of various methods of surface analysis is presented in a table. The article discusses the relationship between wear and reliability in terms of exponential distribution, Weibull distribution, and gamma distribution. It concludes with information on the effects of interaction on failure probability.

This article describes the solid-phase and liquid-phase processes involved in diffusion bonding of metals. It provides a detailed discussion on the diffusion bonding of steels and their alloys, nonferrous alloys, and dissimilar metals. Ceramic-ceramic diffusion welding and a variation on this process in which ceramic powder compacts are simultaneously sintered and bonded are also discussed.

This article provides an overview of surface-texturing techniques. It describes the texturing parameters, namely, shape, depth, and width of the textured pattern, its aspect ratio (depth over width), texture area density, and orientation. The article explains the effect of these parameters on tribological behavior of textured surfaces. It provides information on various modeling approaches for surface texture. The article also discusses the beneficial effect of surface texturing.

This article focuses on friction, lubrication, and wear of internal combustion engine parts, improvements in which provide important gains in energy efficiency, performance, and longevity of the internal combustion (IC) engine systems. It discusses the types, component materials, and Friction and Wear Control of IC engine. The article explains the process of friction reduction by surface textures or coatings. It provides information on surface hardening of iron and steel, which is commonly employed for engine and powertrain components such as crankshafts, cams, and cylinder liners. The article also discusses advanced surface engineering technologies, such as diamondlike carbon coatings and surface texture technology. Information on thermal-spray methods that have led to improvements in engine components is also provided. The article describes IC engine-components wear, namely, piston assembly wear, valvetrain wear, cylinder-bore wear, and engine bearing wear. It concludes with information on inlet valve and seat wear of IC engine.