Method of nondestructive turbine airfoil inspection and repair
Disclosed is a method of detecting mixed mode corrosion of a turbine airfoil. The method includes heat treating the turbine airfoil at a temperature of 1600 to 2100° F. in a Ni/Co oxide reducing atmosphere; and scanning the heat treated turbine airfoil with a magnetometer to determine the presence of mixed mode corrosion, wherein the turbine airfoil comprises a nickel superalloy and has internal passages.
1. A method of detecting mixed mode corrosion of a turbine airfoil having internal passages comprising:
heat treating the turbine airfoil at a temperature of 1600 to 2100° F. (871 to 1149° C.) in a Ni/Co oxide reducing atmosphere; and
scanning an external surface of the heat treated turbine airfoil with a magnetometer to determine the presence of mixed mode corrosion on the internal passages, wherein the turbine airfoil comprises a nickel superalloy.
2. The method of claim 1 , further comprising comparing the results of scanning to a threshold value.
3. The method of claim 1 , wherein heat treating is for 1 to 32 hours.
4. The method of claim 1 , wherein the Ni/Co oxide reducing atmosphere is a vacuum.
5. The method of claim 1 , wherein the Ni/Co oxide reducing atmosphere comprises noble gases, hydrogen, hydrogen fluoride, or a combination thereof.
6. The method of claim 1 , wherein the Ni/Co oxide reducing atmosphere has a partial pressure of oxygen less than or equal to 10 −14 atmospheres (atm) at 1600° F.
7. The method of claim 1 , wherein the turbine airfoil has an existing thermal barrier coating system and heat treating occurs after removing the existing thermal barrier coating system.
8. The method of claim 1 , wherein the turbine airfoil has an existing thermal barrier coating system and heat treating occurs with the existing thermal barrier coating system in place.
9. A method of detecting a turbine airfoil having mixed mode corrosion comprising:
heat treating the turbine airfoil at a temperature of 1600 to 2100° F. (871 to 1149° C.) in a Ni/Co oxide reducing atmosphere; and
scanning an external surface of the heat treated turbine airfoil with a magnetometer to determine the presence of mixed mode corrosion on the internal passages, wherein the turbine airfoil comprises a nickel superalloy and further wherein scanning is performed parallel to an internal passage.
10. The method of claim 9 , further comprising comparing the results of scanning to a threshold value.
11. The method of claim 9 , wherein heat treating is for 1 to 32 hours.
12. The method of claim 9 , wherein the Ni/Co oxide reducing atmosphere is a vacuum.
13. The method of claim 9 , wherein the Ni/Co oxide reducing atmosphere comprises noble gases, hydrogen, hydrogen fluoride, or a combination thereof.
14. The method of claim 9 , wherein the Ni/Co oxide reducing atmosphere has a partial pressure of oxygen less than or equal to 10 −14 atmospheres (atm) at 1600° F.
15. The method of claim 9 , wherein the turbine airfoil has an existing thermal barrier coating system and heat treating occurs after removing the existing thermal barrier coating system.
16. The method of claim 9 , wherein the turbine airfoil has an existing thermal barrier coating system and heat treating occurs with the existing thermal barrier coating system in place.