24 July 2021 Nimonic®
Nimonic PK33 Nickel Based Supperalloy
NIMONIC® alloy PK33 is a vacuum processed nickel-base alloy that was developed to provide a sheet material offering improved ductility in welded assemblies and high creep strength to replace NIMONIC alloys 80A and 90.
NIMONIC alloy PK33 is extremely resistant to thermal shock and thermal fatigue has good weldability and is, therefore, attractive for combustion chambers, jet pipes and reheat systems for high-performance gas turbine engines.
Although the alloy was developed as a sheet material, associated forgings and ring components were also required and it is now standard practice to produce forging billet, bar, and a section for matching using the consumable-electrode vacuum-arc melting process.
The welding techniques for this alloy are similar to those in common use on other nickel-base age-hardenable alloys.
NIMONIC alloy PK33 is normally put into service after a two-stage heat treatment, that is in the solution-treated and age-hardened condition. This heat treatment is generally carried out in the air. The material is usually supplied in the solution-treated condition and is aged by the customer as part of the fabrication process. NIMONIC alloy PK33 can, however, be supplied in any requested heat-treatment condition. Details of the recommended heat treatments for various forms are given below, where the stated times represent the times at temperature. In establishing furnacing time due allowance must, of course, be made for furnace characteristics and charge weight.
Chemical Composition:
| Weight% | Ni | Cr | Mo | Fe | Al | Ti | C |
|---|---|---|---|---|---|---|---|
| PK33 | Bal | 16-20 | 5-9 | 1.0 max | 1.7-2.5 | 1.5-3.0 | 0.07 max |
| Weight% | Cu | Si | Mn | Co | B | Zr | S |
| PK33 | 0.2 max | 0.5 max | 0.5 max | 12.0-16.0 | 0.005 max | 0.06 max | 0.015 max |
Typical Mechanical Properties:
| Material | Condition 20°C | 0.1 % Proof Stress MPa | Tensile Strength MPa | Elongation % | Reduction of Area % |
|---|---|---|---|---|---|
| PK33 Bar | Heat Treatment 2h/1100°C/AC +4h 850°C/AC | 664 | 1127 | 33 | 41 |