Method of making silicon nitride based cutting tools-I

Details Method of making silicon nitride based cutting tools-I Method of making silicon nitride based cutting tools-I

1979-12-20

1981-04-28

Parrish, John

Plastic and nonmetallic article shaping or treating: processes

Including step of generating heat by friction

51307, 51309, 106 65, 106 735, 264 66, 264332, C04B 3558

Patent

active

042645484

ABSTRACT:
A method of making a unitary silicon nitride comprising object and tool is disclosed. A uniform powder mixture of Si.sub.3 N.sub.4 containing SiO.sub.2 as an oxide coating, 4-12% by weight Y.sub.2 O.sub.3, and 0.50-2.5 Al.sub.2 O.sub.3 is prepared. The mixture is hot pressed at a temperature of 1,680.degree.-1,750.degree. C. under a pressure and for a period of time sufficient to produce at least 99.0% (preferably at least 99.5%) of full theoretical density in the mixture to form a pressed object. The heating and pressure is then relieved and the object cooled. The object is heat treated by holding at a temperature in the range of 1,000.degree.-1,400.degree. C. without mechanical pressure for at least 5 minutes but for a time sufficient to provide a nucleating reaction in secondary phases formed as a result of hot pressing. The heat treatment can take place either as an interruption of the cooling cycle or as a subsequent reheat cycle after cooling to room temperature.

REFERENCES:
patent: 3830652 (1974-08-01), Gazza
patent: 3837871 (1974-09-01), Weaver
patent: 3950464 (1976-04-01), Masaki
patent: 3969125 (1976-07-01), Komeya et al.
patent: 4071371 (1978-01-01), Milberg et al.
patent: 4102698 (1978-07-01), Lange et al.
patent: 4143107 (1979-03-01), Ishii

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