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Alpha-alumina ceramic containing zirconium oxynitride dispersion - has surface oxide layer formed at high temperature in oxygen -atmosphere, after or during sintering, for use as high strength cutter.
: Lerch, M.; Wrba, J.; Müller, G.

Frontpage ()

DE 1997-19702384 A: 19970123
DE 1997-19702384 A: 19970123
DE 19702384 A1: 19980730
Patent, Elektronische Publikation
Fraunhofer ISC ()

A dispersion ceramic contains 60-97 wt.% corundum, mullite and/or cordierite and at least 3 wt.% zirconium oxynitride. Also claimed is a process for producing the above dispersion ceramic in which a green body, containing corundum, mullite and/or cordierite and zirconium dioxide, is sintered in a nitrogen-containing atmosphere to form zirconium oxynitride. Preferably, heat treatment not more than 600 deg. C in an oxygen-containing atmosphere is carried out after or during sintering and/or sintering is carried out in an oxygen-containing, preferably calcium borate-containing, crucible. USE - The alpha -Al2O3/zirconium oxynitride dispersion ceramic is used as a cutting ceramic (claimed). ADVANTAGE - The ceramic has high strength and fracture resistance, which are relatively independent of temperature up to about 600 deg. C, and retains good mechanical properties at 600-1000 deg. C during use in machining, due to formation of a self-renewing surface oxidation layer, which induces surface compressive stresses.