Method of making silicon nitride based cutting tools-I
US4264548A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 20, 1979 |
| Grant date | Apr 28, 1981 |
| Priority date | — |
| Expiry date | Dec 20, 1999 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC04B35/593
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
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.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.