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is around 40 MPa ■ m1/2. Some silicon nitride materials now approach 10 MPa ■ m1/2, which is tougher than cast-iron. Some transformation-toughened zirconia materials have toughness around 15 MPa ■ m1/2, which is higher than that of many tungsten carbide-cobalt (WC-Co) cermets. These new tougher ceramics have demonstrated dramatically improved resistance to impact, contact stress, and handling damage and are providing high reliability and durability that users are accustomed to receiving with metals and WC-Co. New continuous fiber-reinforced ceramic composites (CFCCs) are under development that provide further improvements in fracture toughness, as discussed in the next chapter.

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