Densified polymer infiltrated and pyrolysis-based CMC articles
A method of densifying a CMC article includes the steps of pyrolyzing a CMC article until a desired initial porosity is achieved, coating CMC pores within the CMC article with carbon, pyrolyzing the carbon to form carbon pores, coating the carbon pores with silicon, and heat treating the CMC article to create a silicon carbide filled pore integrated with silicon carbide of the CMC article to densify the CMC article.
1. A method of densifying a ceramic matrix composite (CMC) article comprising the steps of:
pyrolyzing a CMC article having a silicon carbide matrix using a polymer infiltrated and pyrolysis (PIP) process until a desired initial porosity of silicon carbide pores within the silicon carbide matrix is achieved, wherein the CMC article is pyrolyzed at a temperature of 1000-1800° C. to achieve the initial porosity within the silicon carbide matrix;
coating silicon carbide pores within the silicon carbide matrix with carbon;
pyrolyzing the carbon using a PIP process to form carbon pores on the silicon carbide matrix, wherein the carbon is pyrolyzed at a temperature of 1000-1800° C.;
coating the carbon pores with silicon; and
heat treating the CMC article to draw the silicon into the carbon pores to react with the carbon and create additional silicon carbide that is integrated with the silicon carbide of the CMC article to densify the CMC article.
2. The method according to claim 1 , wherein the CMC article is pyrolyzed more than once to achieve the initial porosity.
3. The method according to claim 2 , wherein the CMC article is pyrolyzed less than six times to achieve the initial porosity.
4. The method according to claim 1 , wherein the silicon carbide pore coating step includes infiltrating the silicon carbide pores with a carbon precursor resin that provides the carbon.
5. The method according to claim 4 , wherein the carbon precursor resin includes fillers selected from the group including silicon, silicon carbide, boron carbide and silicon nitride.
6. The method according to claim 1 , wherein the silicon enters the carbon pores by capillary action.
7. The method according to claim 1 , wherein the densified article is machined to a desired shape.
8. The method according to claim 7 , wherein a seal coat is applied to the machine shape.
9. The method according to claim 8 , wherein an environmental barrier coating is applied to the seal coating.
10. The method according to claim 1 , wherein the CMC article is densified by infiltrating the article with a silicon carbide precursor resin.
11. The method according to claim 10 , wherein the CMC article pyrolyzing step includes pyrolyzing the CMC article at 1200-1800° C.
12. The method according to claim 10 , wherein the silicon carbide precursor resin includes a filler selected from the group including silicon, silicon carbide, boron carbide and silicon nitride.
13. The method according to claim 1 , wherein CMC fibers are arranged about a form and a silicon carbide precursor resin is injected into a mold to provide the CMC article.
14. The method according to claim 13 , wherein the CMC fibers are wrapped about the form.
15. The method according to claim 13 , wherein the silicon carbide precursor resin includes a filler selected from the group including silicon, silicon carbide, boron carbide and silicon nitride.
16. The method according to claim 13 , wherein the CMC fibers are provided as a prepreg.
17. The method according to claim 13 , wherein the CMC article in the mold is heated to a temperature of 100-600° C. and is removed from the mold.
18. The method according to claim 13 , wherein the CMC article is placed in a fixture during the CMC article pyrolyzing step to a temperature of 1000-1400° C.