Quasicrystalline alloys and their use as coatings

1. An icosahedral, quasicrystalline compound, or compound present in the form of an approximant, having the nominal composition:

Ti v Cr w Al x Si y O z

in which

v=60-65

w=25-30

x=0-6

y=8-15

z=8-20

and in which the atom percent of oxygen is in the range of 8 to 15%, and the atom percent of aluminum is in the range of 2 to 5%.

2. A compound according to claim 1 , wherein

v=60

w=30

x=0-3

y=8-15

z=8-20

in which the atom percent of oxygen is in the range of 8 to 12%, and the atom percent of aluminum is in the range of 1.5 to 3%.

3. A compound in accordance with claim 2 , wherein y=8-10.

4. A compound in accordance with claim 2 , wherein z=8-10.

5. A compound according to claim 1 , wherein

v=60

w=30

x=0-2

y=8-10

in which the atom percent of oxygen is in the range of 10%, and the atom percent of aluminum is in the range of 1.5 to 2.5%.

6. A compound according to claim 1 , comprising at least one composition selected from the group consisting of: Ti 60 Cr 32 Si 4 (SiO 2 ) 4 ; Ti 60 Cr 25 Si 5 (SiO 2 ) 10 ; Ti 65 Cr 25 Si 2.5 (SiO 2 ) 7.5 ; Ti 60 Cr 30 (SiO 2 ) 10 ; Ti 60 Cr 30 Al 2 Si 3 (SiO 2 ) 5 ; Ti 60 Cr 30 Al 3 Si 2 (SiO 2 ) 5 ; Ti 60 Cr 30 Al 2 Si 3 (SiO 2 ) 5 ; and Ti 60 Cr 30 Si 5 (SiO 2 ) 5 .

7. A method for manufacturing the compound of claim 1 comprising:

selecting the components of the compound; and fusing the components in a cover gas or vacuum.

8. A method according to claim 7 , wherein fusing comprises fusing in an arc.

9. A method according to claim 7 , further comprising:

applying the compound as a coating to a material, wherein applying comprises plasma spray or vapor deposition, followed optionally by tempering.

10. A method according to claim 7 , further comprising:

tempering the compound after fusing.

11. A method according to claim 10 , wherein tempering comprises tempering in steps, said steps comprising graduated increases in temperature, graduated decreases in temperature, or combinations thereof.

12. A method in accordance with claim 10 , wherein tempering comprises tempering in a furnace, and further comprising cooling in the furnace.

13. A method in accordance with claim 10 , wherein tempering comprises tempering at a temperature in the range of between 1000 and 1300° C., for a period of 80 to 200 hours.

14. A method in accordance with claim 10 , wherein tempering comprises tempering for 7 days at 1100° C.

15. A method of use of the compound of claim 1 comprising:

exposing the compound to temperatures and gases present in a gas turbine or compressor.

16. A method of use of a compound according to claim 15 , wherein exposing comprises exposing as a component of a gas turbine or of a compressor.

17. A method in accordance with claim 16 , wherein the component comprises a rotor blade or a guide vane of a gas turbine or of a compressor.

18. A method of use according to claim 15 wherein the compound comprises a coating on a surface directly exposed to the gases, and further optionally comprising a second functional layer made of said material disposed underneath the coating for providing adhesion and as an additional barrier.

19. A method of use according to claim 18 , wherein the coating has a thickness in the range of between 10-400 μm.

20. A method in accordance with claim 19 , wherein the coating has a thickness in the range of between 100 to 200 μm.