Ceramics, Refractory And Abrasive Materials
Introduction
There are some situations in practice where high temperatures are occupied. Besides creating that temperatures engineers are termed as for utilizing materials that are least affected via such temperatures hence usefulness and integrity of equipment might be maintained. Furnaces for melting and heating metals and alloys, boilers for evaporating water, combustion chambers for gaseous fuels and burning liquid and ladles for holding liquid metals are some instances where high temperatures are essentially existing. Reentry vehicles or entering earth's atmosphere from space and blades of gas turbine are the examples of parts and structure subjected also to high temperature. Hence engineering practice demands production and employ of materials that will be capable to withstand such temperatures whilst maintaining their properties, dimensional and integrity stability. Refractory are those materials such can withstand that temperatures. Most of refractory materials are nitrides, carbides, oxides and borides.
It should be noted that most elementary metals cannot be utilized for the causes of high temperature applications since they themselves melt or become soft. Though, there are some metals that melt at higher temperature and they as of high melting alloys.
Such metals which melt above 2450oC are classified as refractory metals, niobrium, molybdenum, tantalum and tungsten are examples.
Abrasive machining processes are utilized either for removing very hard surfaces or for producing very smooth and closely finished surfaces or both. Abrasive wheels are made up of very small hard abraiding particles, each of while serves as a small cutter and hence removes a very fine chip. The abrasive materials employed for making abrasive tools are diamond, silicon carbide and aluminium oxide.
Several inorganic materials identified for temperature resistance are very brittle and can carry only minute tensile stresses. They are utilized for their thermal and electrical resistances and are capable of being formed in various shapes and sizes. Those types of materials are ceramics, glasses and cements. Fortunately their tensile properties can be enhanced by fibre reinforcement.