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TEXT 6B

Composite Ceramics

Advanced ceramic materials have such interesting properties that mechanical engineers are becoming more and more interested in their use as structural parts (конструкционные детали).

Ceramic cutting tools have been in use for some time. However, it is only during the last twenty years that there have been rapid development in this field because of the development of new composite ceramics.

Composite materials are materials in which two or more different substances, such as metals, ceramics, glasses, or polymers are combined without chemical reaction. As a result one can produce a material with properties different from those of any of the individual constituents. The constituents of a composite would retain their individual charac­teristics.

Recently engineers have developed various kinds of composite ceramics which must combine an increased toughness (пластичность) with the same hardness and strength of usual ceramics. A promising recent development is the addition of a tiny quantity of metal to increase toughness and tool life. Thus, at room and high temperatures ( 1000°C) the composite ceramics for cutting tools should possess the following properties: high strength, high toughness, high hardness, high thermal shock resistance and high chemical inertness.