Abradable layer with glass microballoons
A gas turbine engine includes a circumferential row of blades, with the blades having respective blade tips. A seal is disposed about the blades. The seal has an abradable layer which the tips of the blades, at times, rub against when the blades rotate. The rubbing produces a maximum temperature at the abradable layer. The abradable layer includes a metal matrix and microballoons dispersed in the metal matrix. The microballoons are formed of a glass that has a glass transition temperature that is approximately 50° F. to 300° F. greater than the maximum temperature.
1. A gas turbine engine comprising:
a circumferential row of blades, the blades having respective blade tips; and
a seal disposed about the blades, the seal having an abradable layer which the tips of the blades, at times, rub against when the blades rotate, there being a maximum temperature at the abradable layer without rubbing, the abradable layer including,
a metal matrix, and
microballoons dispersed in the metal matrix, the microballoons being formed of a glass having a glass transition temperature that is approximately 50° F. to 300° F. greater than the maximum temperature.
2. The gas turbine engine as recited in claim 1 , wherein the metal matrix is formed from an alloy and the alloy is a nickel- or cobalt-based alloy.
3. The gas turbine engine as recited in claim 1 , wherein the alloy is copper-based alloy.
4. The gas turbine engine as recited in claim 1 , wherein the alloy is aluminum-based alloy.
5. The gas turbine engine as recited in claim 1 , wherein the glass is fluoroaluminate glass.
6. The gas turbine engine as recited in claim 1 , wherein the glass is tellurium dioxide glass.
7. The gas turbine engine as recited in claim 1 , wherein the glass is borosilicate glass.
8. The gas turbine engine as recited in claim 1 , wherein the glass is soda-lime glass.
9. The gas turbine engine as recited in claim 1 , wherein the glass is fused quartz glass.
10. The gas turbine engine as recited in claim 1 , wherein the abradable layer has, by volume, 10-60% of the microballoons.
11. The gas turbine engine as recited in claim 1 , wherein the abradable layer further comprises a lubricant.
12. The gas turbine engine as recited in claim 1 , wherein the circumferential row of blades are part of a compressor or turbine section of the gas turbine engine.
13. The gas turbine engine as recited in claim 11 , wherein the lubricant is boron nitride.
14. The gas turbine engine as recited in claim 13 , wherein the abradable layer includes up to about 10% by volume of boron nitride particles.
15. The glass turbine engine as recited in claim 2 , wherein the alloy is MCrAlY, wherein M is either cobalt or nickel.
16. The gas turbine engine as recited in claim 15 , wherein a combined amount of aluminum and chromium is greater than 15% by weight.
17. The gas turbine engine as recited in claim 3 , wherein the alloy includes at least 35% of copper by weight.
18. The gas turbine engine as recited in claim 4 , wherein the alloy is a eutectic composition having 12% silicon by weight.
19. The gas turbine engine as recited in claim 4 , wherein the alloy is a Cu—Ni—Cr—Al alloy.