Plastic and nonmetallic article shaping or treating: processes – Including step of generating heat by friction
Patent
1992-12-31
1994-08-30
Silbaugh, Jan H.
Plastic and nonmetallic article shaping or treating: processes
Including step of generating heat by friction
264 65, 264 66, 501 87, C04B 3510, C04B 3552
Patent
active
053425642
ABSTRACT:
A method of making a sintered ceramic body for applications such as wear resistant parts and cutting tools. A green body is prepared from a powder mixture including alumina, TiC or (Ti(C,N)), a densification aid, and TiO.sub.2. The weight ratio of alumina to TiC in the body is about 40:60 to about 95:5; that of TiO.sub.2 to alumina plus TiC is 0:100 to about 2:98. The green body is rapid sintered by heating in a sintering atmosphere to about 1800.degree.-1920.degree. C. for a time sufficient to achieve a density of at least about 4.20 g/cc. The heating rate above about 800.degree. C. is between about 120.degree. C./min and the rate at which the green body experiences thermal shock. The sintering atmosphere is Ar-H.sub.2 or N.sub.2 -H.sub.2 in a molar ratio of Ar or N.sub.2 to H.sub.2 of about 92:8 to 100:0. Carbon monoxide is introduced to the sintering atmosphere only after the sintering temperature exceeds about 1400.degree. C. The amount of CO introduced is selected to inhibit reaction between the alumina and TiC. The CO may be introduced by placing a mass of graphite including adsorbed oxygen and water in the furnace at initiation of sintering such that the mass releases CO only after the sintering temperature exceeds 1400.degree. C. The body may be prepared from a homogeneous slurry, which is dried and shaped to form a green body having a density of at least about 30% of theoretical. The green body may be presintered, isopressed to collapse any cracks, macroscopic pores, or voids, and sintered or sintered and hot-isostatic-pressed.
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Walsh John
Wei George C.
Fiorilla Christopher A.
Panagos Bill C.
Silbaugh Jan H.
Valenite Inc.
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