High-temperature materials and mechanisms: Applications and challenges

Abstract

An important tool in processing materials is to subject them to high temperatures and to use the resulting change in properties, which includes softening or melting, and changes in chemical and material phase. Thus, it is feasible to perform desired modifications in the material shape and characteristics. Other applications of high temperatures include heating, power harvesting, and other energy-related tasks. As covered in the various chapters of this book, there are many examples of operations that are implemented when materials are subjected to high temperatures, including forming and casting. To operate at extremely high temperatures, there is a need for devices, tools, structures, and mechanisms that are used to operate at such conditions. High-temperature materials have been used by humans as early as the primitives have started using fire and heat. The materials that are used have grown in capability and sophistication from as simple as rocks to the enormous selection that is available today (Bar-Cohen, 2003; Spear et al., 2006). The pool of high temperature (HT) materials that are available nowadays includes metal alloys such as stainless steels, superalloys, and refractory metals as well as ceramics, composites, and nano-carbon-based materials. The application of high-temperature materials has been expanded from food preparation and heating to fabrication processes and applications that require sustaining enormously high temperatures for extended periods of time. Examples of applications of high-temperature materials include aircraft jet engines, industrial gas turbines, hypersonic aircraft structures, power generators and nuclear reactors, space entry heat shields, as well as furnaces, ducting, electronics, and lighting devices (Wuchina et al., 2007). The requirements for materials and the material selection are dictated by the service operation conditions, as well as the ability of the selected materials to sustain the exposure over extended periods while being subjected to forces, pressures, corrosive conditions, and torques (in spikes, cycles, or constant levels). As the operating temperatures increase, there are fewer material choices that are available. The range of applications where high temperatures are used is quite large and some were covered in the previous chapters of this book. The focus of this chapter is on providing a brief review of some of the major and/or critical applications.