Advanced Materials and Structures for Extreme Operating Conditions
Increasing industrial demands for high temperature applications, high t- perature gradients, high heat cycle resistance, high wear resistance, impact resistance, etc., require application of new materials. Conventional met- lic materials, such as steels, nickel- and aluminium-based alloys, etc. c- not resist such extreme operating conditions. They have to be replaced by new metal/matrix or ceramic/matrix composite materials, MMC or CMC, such as titanium/zirconia,titanium/alumina, nickel/zirconia,nickel/alumina, steel/chromium nitride MMCs, or titanium carbide/silicon carbide, alumina/ zirconiaCMCs,etc. Forinstance,zirconia-basedmaterialsareknownforgood thermal insulation, but are bad for oxygen insulation, alumina-based mate- als are good for oxygen insulation and relatively good for thermal insulation, chromium nitride materials are used for good wear resistance due to their high hardness and not so bad thermal insulation, to mention only some. In general, aluminium matrix composites have a useable temperature upward of ? ? 300 C, whereas titanium matrix composites can be safely used up to 800 C. ? For higher temperature applications, up to 2000 C or even more, ceramic matrix composites have to be used. In spite of good thermal, wear and an- oxygen properties of ceramics, their mechanical properties are rather poor, mainly due to high brittleness and low toughness resistance. The ?rst methods to improve thermal, wear, oxygen, etc. resistance of metallic structures, without suppressing their strength and toughness, c- sisted in depositing thin layers of appropriate ceramics on the metallic s- strate, to produce thermal, wear or oxygen barrier coatings T/W/O BCs.
Includes composite materials which are highly important for modern applications