US4264548A
Expired / Lapsed
US
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Method of making silicon nitride based cutting tools-I
Assignee: Ceradyne Inc
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Filing: 1979-12-20
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Granted: 1981-04-28
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Expires: 1999-12-20
Abstract
Abstract A method of making a unitary silicon nitride comprising object and tool is disclosed. A uniform powder mixture of Si 3 N 4 containing SiO 2 as an oxide coating, 4-12% by weight Y 2 O 3 , and 0.50-2.5 Al 2 O 3 is prepared. The mixture is hot pressed at a temperature of 1,680°-1,750° 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°-1,400° 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.
Inventors
- 👤 Andre Ezis
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 17:55
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/593
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
134 words
A method of making a unitary silicon nitride comprising object by the steps comprising: (a) uniformly mixing silicon nitride powder containing SiO 2 as an oxide surface coating, 4-12% by weight Y 2 O 3 powder, and 0.50-2.5% Al 2 O 3 , (b) hot pressing the mixture at a temperature of 1,680°-1,750° C. under a pressure and for a period of time sufficient to produce at least 99.0% of full theoretical density in said mixture to form a pressed object (c) relieving said heating and pressure on said object and cooling and (d) heat treating said object by holding at a temperature in the range of 1,000°-1,400° C. without mechanical pressure for at least 5 minutes but sufficient to provide a nucleating reaction in secondary phases formed as a result of hot pressing.
Claim 2
Independent Claim
134 words
A method of making a unitary silicon nitride comprising object by the steps comprising: (a) uniformly mixing silicon nitride powder containing SiO 2 as an oxide surface coating, 4-12% by weight Y 2 O 3 powder, and 0.50-2.5% Al 2 O 3 , (b) hot pressing the mixture at a temperature of 1,680°-1,750° C. under a pressure and for a period of time sufficient to produce at least 99.0% of full theoretical density in said mixture to form a pressed object (c) relieving said heating and pressure on said object and cooling and (d) heat treating said object by holding at a temperature in the range of 1,000°-1,400° C. without mechanical pressure for at least 5 minutes but sufficient to provide a nucleating reaction in secondary phases formed as a result of hot pressing.
Claim 3
Dependent Claim
29 words
The method as in claim 1 in which; the cooling step (c) is carried out to room temperature and said object is reheated to the temperature of step (d).
Claim 4
Dependent Claim
35 words
The method as in claim 1 in which the cooling of step (c) is interrupted before the temperature of the object descends through the temperature range of 1,400°-1,000° C. and step (d) is carried out.
Claim 5
Dependent Claim
21 words
The method as in claim 1 in which step (d) is carried out for a period of time of 10-300 minutes.
Claim 6
Dependent Claim
26 words
The method as in claim 1 in which said mixture is precompacted under a light pressure of about 500 psi and between steps (a) and (b).
Claim 7
Dependent Claim
20 words
The method as in claim 1 in which steps (b) through (c) are carried out under a flowing nitrogen atmosphere.
Claim 8
Dependent Claim
17 words
The method as in claim 1 in which said silicon nitride powder contains 0.5-3.5% SiO 2 .
Claim 9
Dependent Claim
24 words
A method for making a cutting tool as in claim 1 which additionally comprises the step of shaping said object as a cutting tool.
Claim 10
Dependent Claim
20 words
The method as in claim 1 in which the hot pressing is carried out for a period of 15-45 minutes.
Claim 11
Independent Claim
140 words
A method of making a unitary silicon nitride comprising object by the steps comprising: (a) uniformly mixing silicon nitride powder containing SiO 2 as an oxide surface coating, 4-12% by weight Y 2 O 3 powder, and 0.50-2.5% Al 2 O 3 , (b) hot pressing the mixture at a temperature of 1,680°-1,750° C. under a pressure and for a period of time sufficient to produce at least 99.0% of full theoretical density in said mixture to form a pressed object, (c) relieving said heating and pressure on said object and cooling, and (d) heat treating said object by holding at a temperature in the range of 1,000°-1,400° C. without mechanical pressure for at least 5 minutes but sufficient to provide a nucleating reaction in secondary phases formed as a result of hot pressing to form a multicrystalline phase object.
Claim 12
Independent Claim
140 words
A method of making a unitary silicon nitride comprising object by the steps comprising: (a) uniformly mixing silicon nitride powder containing SiO 2 as an oxide surface coating, 4-12% by weight Y 2 O 3 powder, and 0.50-2.5% Al 2 O 3 , (b) hot pressing the mixture at a temperature of 1,680°-1,750° C. under a pressure and for a period of time sufficient to produce at least 99.0% of full theoretical density in said mixture to form a pressed object, (c) relieving said heating and pressure on said object and cooling, and (d) heat treating said object by holding at a temperature in the range of 1,000°-1,400° C. without mechanical pressure for at least 5 minutes but sufficient to provide a nucleating reaction in secondary phases formed as a result of hot pressing to form a multicrystalline phase object.
Claim 13
Dependent Claim
20 words
The method as in claim 10 in which the hot pressing is carried out for a period of 15-45 minutes.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1984-04-27 | 1984-10-27 | 1985-04-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-04-27 | 1988-10-27 | 1989-04-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-04-27 | 1992-10-27 | 1993-04-28 | $7700.00 | Window Closed / Lapsed |