Metal particles were frequently detected in the oil of an aircraft engine, triggering an investigation that led to a torque sensor and its mounting components. The sensor assembly was removed and examined in greater detail. As the chapter explains, investigators discovered that one of the bearings had been subjected to excessive friction, evidenced by brinelling, metal flow, heat tinting, deformation, and wear. They also observed extensive grooving on a retaining plate and several washers matching the diameter of the outer bearing races. Based on their findings, investigators concluded that excessive clearance allowed the outer bearing races to rotate, thus removing material from adjacent contact surfaces and accelerating the buildup of metal particles in the engine oil. The chapter recommends several design changes to remedy the problem.

A pair of bearings mounted side by side in an aircraft engine failed in service. Photographs show that the inner rings were either broken or deformed, the balls were worn and flattened, and the cages severely damaged. The bearing races were damaged as well, but only on one side indicating a directional thrust. In addition to their examination, investigators also conducted metallographic studies and hardness tests, which indicated that the balls and inner rings reached temperatures above 825 °C (1520 °F). Based on their findings, investigators concluded that the bearings failed due to overheating, possibly as a result of misalignment compounded by insufficient lubrication and high speeds.

Prior to forging, it is often necessary to preform billet stock to achieve adequate material distribution. This chapter discusses the equipment used for such operations, including transverse rolling machines, electric upsetters, ring-rolling mills, horizontal presses, and rotary (orbital) and radial forging machines. It describes their basic operating principles as well as advantages and disadvantages.

This chapter is largely a compendium of best practices and procedures for minimizing the effects of fatigue. It explains how to make products more resistant to fatigue by choosing the right materials and manufacturing processes, avoiding geometries and features that concentrate strains, preventing or removing surface damage, and by inducing compressive mean stresses that prolong fatigue life. It also discusses the use of property conditioning and restoration treatments, the benefits of interference fits and processes such as coaxing, the effects of assembly damage and operating overload, the importance of surface cleanliness and finish, and the role of inspection, testing, replacement, and repair in safe-life and fail-safe designs. Examples highlighting the benefits and potential pitfalls of proof loading tests are included as well.

Ferritic nitrocarburizing accomplishes surface treatment of a part in the ferrite region of the iron-carbon equilibrium diagram. This chapter presents the history and process benefits of ferritic nitrocarburizing.

This chapter discusses the important role of metallography and the metallographer in predicting and understanding the properties of metals and alloys. Examples are presented of a metallographer working as part of a team in a research laboratory of a large steel company and a metallographer working alone at a small iron foundry. The three basic areas in all metallography laboratories are discussed: the specimen preparation area, the polishing/etching area, and the observation/micrography area. Important safety issues in a metallographic laboratory are also considered.

The wear caused by contact stress fatigue is the result of a wide variety of mechanical forces and environments. This chapter discusses the characteristics of four types of contact stress fatigue on mating metal surfaces: surface, subsurface, subcase, and cavitation. Features and corrective actions for these contact stress fatigue are discussed. The chapter also lists some possible ways to reduce the cavitation fatigue problem.

This chapter reviews various ways to classify failure categories and summarizes the basic types, causes, and mechanisms of damage, with particular consideration given to whether the likelihood of the types of damage can or cannot be influenced by the heat treating of steel parts. The classical organization for types of damage (failures) is as follows: deformation, fracture, wear, corrosion or other environmental damage, and multiple or complex damage. The chapter also provides some examples of lack of conformance to specification that may at first look like the heat treater did something wrong, but where other contributing factors made it difficult or impossible for the heat treater to meet the specification.

This chapter discusses the causes and effects of wear along with prevention methods. It covers abrasive, erosive, erosion-corrosion, grinding, gouging, adhesive, and fretting wear. It also discusses various forms of contact-stress fatigue, including subsurface-origin fatigue, surface-origin fatigue, subcase-origin fatigue (spalling fatigue), and cavitation fatigue.

This chapter concerns itself with the tribology of ceramics, cermets, and cemented carbides. It begins by describing the composition and friction and wear behaviors of aluminum oxide, silicon carbide, silicon nitride, and zirconia. It then compares and contrasts the microstructure, properties, and relative merits of cermets with those of cemented carbides.

This chapter reviews the types of friction that are of concern in tribological systems along with their associated causes and effects. It discusses some of the early discoveries that led to the development of friction laws and the understanding that friction is a system effect that can be analyzed based on energy dissipation. It describes the stick-slip behavior observed in wiper blades, the concept of asperities, and the significance of the shape, lay, roughness, and waviness of surfaces in sliding contact. It explains how friction forces are measured and how they are influenced by speed, load, and operating environment. It also covers rolling contact and fluid friction and the effect of lubrication.

The technology of fabricating composite hardware and structures by filament winding has evolved empirically through the development and manufacturing of specific components. This chapter reviews areas of technology used in building composite parts and discusses the processes from which the current technology was derived. The discussion covers quality control requirements for composite fabrication technology and cleanliness standards in the workplace. It describes technology developed for specific components, including satellites struts, aircraft hydraulic cylinders, drill pipe, drive shafts, couplings, and cryogenic tubing.

This chapter discusses the formation of free carbides and their effect on case-carburized components. It explains how alloying elements influence the composition and structure of carbide phases produced at cooling rates typical of carburizing process. It describes the morphology and distribution of the various types of carbides formed and explains how they affect mechanical properties such as hardness, residual stresses, fatigue and fracture behaviors, and wear resistance. It also provides guidance for determining what processing conditions to avoid and when and why parts should be rejected.

The low-alloy special-purpose tool steels, designated as group L steels in the AISI classification system, are similar to the water-hardening tool steels but have somewhat greater alloy content. This chapter discusses the metallurgy and performance of low-alloy special-purpose tool steels, including those with high carbon content, those with medium carbon content, and those containing nickel.

Quenching is a critical step in the production of hardened steel. This chapter untangles some of the complexities of the quenching process and its effect on the microstructure and properties of various steels. Making extensive use of cooling curves, it sheds light on the transformations that occur at different cooling rates and the extent to which they can be changed by adjusting quench parameters. It discusses the role of quenching in martempering and austempering along with related problems such as cracking and distortion and the challenges posed by low-hardenability steels. It also discusses the use of various quenchants, including oil, polymer, and molten salt, and explains how to measure and compare their performance using a standard (ISO 9950) test.

This chapter discusses the effect of friction in the context of design. It explains how friction coefficients are determined and how they are used to make sizing and selection decisions. It covers practical issues associated with rolling friction, the use of lubricants, and the tribology of metal, ceramic, and polymer surfaces in contact. It also discusses the nature of rolling friction and provides helpful design guidelines.

Liquid penetrant, magnetic particle, and eddy current inspection are used to detect surface flaws. This chapter is a detailed account of the physical principles, process description, equipment requirements, selection criteria, advantages, limitations, and applications of these surface flaw detection techniques.