Heat treatments for improved ductility of Ni—Cr—Co—Mo—Ti—Al alloys

1. A method for heat treating alloy compositions containing in weight percent:

18.5 to 20.5 

chromium

 9.0 to 11.0

cobalt

8.0 to 9.0 

molybdenum

1.38 to 1.65 

aluminum

up to 1.5

iron

1.90 to 2.30 

titanium

0.04 to 0.08 

carbon

 up to 0.15

silicon

 up to 0.015

phosphorus

 up to 0.015

sulfur

0.003 to 0.010 

boron

up to 0.2

niobium

up to 0.5

tungsten

up to 0.1

tantalum

up to 0.1

copper

up to 0.3

manganese

up to 0.1

zirconium

balance

nickel

comprising:

heating the alloy composition at a temperature between 1550° F. and 1750° F. for at least two hours, and

then heating the alloy composition at a lower temperature between 1300° F. and 1550° F. for at least two hours,

thereby forming an alloy composition having a complex grain boundary layer containing gamma prime and M 23 C 6 carbide.

2. The heat treatment method of claim 1 also comprising heating the alloy composition at a temperature between 1850° F. and 1950° F. for at least one hour before heating the alloy composition at a temperature between 1550° F. and 1750° F.

3. The method of claim 1 wherein the step of heating the alloy composition at a temperature between 1550° F. and 1750° F. is comprised of heating the alloy composition at a temperature of 1650° F. and is held at that temperature for 4 hours.

4. The method of claim 1 wherein the step of heating the alloy composition at a temperature between 1300° F. and 1550° F. is comprised of heating the alloy composition at a temperature of 1450° F. for 8 hours.

5. The method of claim 1 also comprising heating the alloy composition at a temperature of 1850° F. for 2 hours prior to the step of heating the alloy composition at a temperature between 1550° F. and 1750° F.

6. The method of claim 1 wherein the alloy composition after heat treatment exhibits improved tensile ductility at a temperature of 1400° F. when compared to a tensile ductility of the alloy composition treated according to a standard heat treatment of 1850° F. for 2 hours followed by 1450° F. for 8 hours.

7. The heat treatment method of claim 1 comprising heating the alloy composition at a temperature between 1550° F. and 1700° F. for at least four hours, also comprising heating the alloy composition at a temperature between 1850° F. and 1950° F. for at least one hour before heating the alloy composition at a temperature between 1550° F. and 1700° F.

8. The method of claim 7 wherein the step of heating the alloy composition at a temperature between 1550° F. and 1700° F. is comprised of heating the alloy composition at a temperature is 1650° F. and is held at that temperature for 4 hours.

9. The method of claim 7 wherein the step of heating the alloy composition at a temperature between 1300° F. and 1550° F. is comprised of heating the alloy composition at a temperature is 1450° F. for 8 hours.

10. The method of claim 7 also comprising heating the alloy composition at a temperature of 1850° F. for 2 hours prior to the step of heating the alloy composition at a temperature between 1550° F. and 1700° F.

11. The method of claim 1 comprising, heating the alloy composition at a temperature between 1550° F. and 1750° F. for at least six hours.

12. The heat treatment method of claim 11 also comprising heating the alloy composition at a temperature between 1850° F. and 1950° F. for at least one hour before heating the alloy composition at a temperature between 1550° F. and 1750° F.

13. The method of claim 11 wherein the step of heating the alloy composition at a temperature between 1550° F. and 1750° F. is comprised of heating the alloy composition at a temperature of 1650° F.

14. The method of claim 11 wherein the step of heating the alloy composition at a temperature between 1350° F. and 1500° F. is comprised of heating the alloy composition at a temperature of 1450° F. for 8 hours.

15. The method of claim 11 also comprising heating the alloy composition at a temperature of 1850° F. for 2 hours prior to the step of heating the alloy composition at a temperature between 1550° F. and 1750° F.

16. The method of claim 1 wherein the alloy composition after heat treatment exhibits an improved containment factor at a temperature of 1400° F. when compared to a containment factor at a temperature of 1400° F. of the alloy composition treated according to a standard heat treatment of 1850° F. for 2 hours followed by 1450° F. for 8 hours.

17. The method of claim 1 wherein the step of heating the alloy composition at a temperature between 1550° F. and 1750° F. is comprised of heating the alloy composition at a temperature of at least 1600° F. and the alloy composition is the held at that temperature for at least 2 hours.