Methods to eliminate mudcracks in cmc matrix by humidity controlled atmosphere
AssigneeRolls-Royce High Temperature Composites Inc.
InventorsPathikumar Sellappan, Sungbo Shim
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Abstract
Methods of reducing dry crack formation in ceramic matrix composite green bodies are provided. Some of the methods expose the green body to a gaseous atmosphere at a relatively high humidity for a first period, and then slowly lower the humidity over a second period, where the gaseous atmosphere is at room temperature for both periods. Other methods start the gaseous atmosphere at room temperature and then raise the temperature to a higher temperature while the humidity is relatively high, and hold that temperature even as the humidity is lowered in the second period.
Claims20
A method of reducing dry crack formation, the method comprising:
- exposing an outer surface of a green body to a gaseous atmosphere having a first humidity for a first period of time at room temperature, the green body being a slurry-infiltrated ceramic fiber preform, the first humidity being a relative humidity within a range of about 40 percent to 100 percent, the first period of time being within a range of about six hours to about 12 hours;
- and
- reducing the humidity of the gaseous atmosphere, while the outer surface of the green body is exposed to the gaseous atmosphere at room temperature, from the first humidity to a second humidity over a second period of time, the second humidity being a relative humidity within a range of about 50 percent to about 65 percent or within a range of about 45 percent to about 60 percent, the second period of time being within a range of about 12 hours to about 18 hours.
A method of reducing dry crack formation, the method comprising:
- exposing an outer surface of a green body for a first period of time to a gaseous atmosphere having a first humidity, the first humidity being a relative humidity within a range of about 50 percent to 100 percent, the first period of time being within a range of about 10 hours to about 16 hours, the green body being a slurry-infiltrated ceramic fiber preform;
- holding the gaseous atmosphere at a first temperature during a first part of the first period of time, the first temperature being room temperature, the first part of the first period of time being within a range of about 10 hours to about 14 hours;
- increasing the temperature of the gaseous atmosphere from the first temperature to a second temperature over a second part of the first period of time, the second part of the first period of time being within a range of about 1.0 hours to 2.5 hours, the second temperature with a range of about 80° C. to about 100° C.;
- holding the temperature at the second temperature over a third part of the first period of time, the third part of the first period within a range of about 1.5 hours to 2.5 hours;
- and
- reducing the humidity of the gaseous atmosphere from the first humidity to a second humidity over a second period of time at the second temperature, the second humidity being a relative humidity within a range of about 50 percent to about 65 percent or within a range of about 45 percent to about 60 percent, the second period of time being within a range of about 8 hours to about 14 hours.
Dependencies are inferred from the claim text.