Claims
- 1. A method of making a unitary silicon nitride cutting tool comprising object, comprising:
- (a) placing in a hot pressing environment a controlled mixture consisting essentially of Si.sub.3 N.sub.4, Y.sub.2 O.sub.3, Al.sub.2 O.sub.3, and SiO.sub.2, wherein said Al.sub.2 O.sub.3 is present in an amount of 0.5-2.5% by weight of the mixture and Y.sub.2 O.sub.3 comprises about 7% to about 9% by weight of said mixture and the Y.sub.2 O.sub.3 /SiO.sub.2 weight ratio therein is at least about 1.6, said controlled mixture being further comprised of a first part, a second part, and a third part said first part consisting essentially of substantially alpha phase Si.sub.3 N.sub.4 and SiO.sub.2 containing less than about 1.0% by weight cation impurities excluding free silicon, said second part consisting essentially of Y.sub.2 O.sub.3, said third part consisting essentially of Al.sub.2 O.sub.3 ;
- (b) hot pressing said controlled mixture at a temperature and pressure and for a time sufficient to compact and react said controlled mixture into a unitary silicon nitride comprising object having a density of at least about 3.25 g/cm.sup.3 ; and
- (c) cooling the resultant unitary object.
- 2. A method in accordance with claim 1, wherein said Y.sub.2 O.sub.3 /SiO.sub.2 weight ratio is at least about 2.5.
- 3. A method in accordance with claim 1, wherein said first powder contains about 0.5 to about 1.5% by weight O.sub.2.
- 4. A method in accordance with claim 2, wherein said first powder contains less than 0.5% by weight cation impurities excluding free silicon.
- 5. A method of making a unitary silicon nitride cutting tool comprising object, comprising:
- (a) placing in a hot pressing environment a controlled powder mixture consisting essentially of Si.sub.3 N.sub.4, Y.sub.2 O.sub.3, SiO.sub.2 and 0.5-2.5% by weight milling media selected from the group consisting of Al.sub.2 O.sub.3, WC, TiC and Si.sub.3 N.sub.4, wherein said Y.sub.2 O.sub.3 comprises about 4% to about 12% by weight of said controlled powder mixture and the Y.sub.2 O.sub.3 /SiO.sub.2 weight ratio therein is at least about 1.6, said controlled powder mixture being further comprised of a first powder, a second powder, and a third powder said first powder consisting essentially of substantially alpha phase Si.sub.3 N.sub.4 and SiO.sub.2 containing less than about 1.0% by weight cation impurities excluding free silicon and containing up to about 0.7% by weight oxygen combined as SiO.sub.2, said second powder consisting essentially of Y.sub.2 O.sub.3 said third powder consisting essentially of said selecting milling media;
- (b) hot pressing said controlled mixture at a temperature and pressure and for a time sufficient to compact and react said controlled powder mixture into a unitary silicon nitride comprising object having a density of at least about 3.25 g/cm.sup.3 ; and
- (c) cooling the resultant unitary object.
Priority Claims (3)
Number |
Date |
Country |
Kind |
54-40425 |
Apr 1979 |
JPX |
|
326356 |
Apr 1979 |
CAX |
|
45597 |
May 1979 |
AUX |
|
RELATED APPLICATIONS
This application is a continuation-in-part of U.S. Ser. No. 911,256, filed May 31, 1978, now abandoned, by the same inventors as the present application.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
3830652 |
Gazza |
Aug 1974 |
|
Non-Patent Literature Citations (1)
Entry |
Smith, "Temperature and Compositional Stability of a Y.sub.6 Si.sub.6 O.sub.21 Phase in Oxidized Si.sub.3 N.sub.4 ", Oct. 1977, pp. 465-466. |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
911256 |
May 1978 |
|