Dec 10 2012
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Fabrication and Heat Treatment
Annealing
Cold Working
Welding
Forming
Machinability
Heat Treatment
Hardening
Applications
Introduction
Super alloys or high performance alloys are of three types namely iron-based, cobalt-based and nickel-based alloys. These alloys are of different shapes and have good oxidation and creep resistance. Super alloys can function under high mechanical stress and high temperatures, and also in places that require high surface stability. Super alloys can be strengthened by precipitation hardening, solid-solution hardening and work hardening methods.
Nimonic PK33™ is a nickel-chromium-cobalt alloy suitable for high temperature strength. Additions of aluminum and titanium during heat treatment hardens this alloy. The following datasheet provides an overview of Nitronic 30™.
Chemical Composition
The chemical composition of Nimonic PK33™ is outlined in the following table.
|
Element |
Content (%) |
|
Nickel, Ni |
54 |
|
Chromium, Cr |
16.0-20.0 |
|
Cobalt, Co |
12.0-16.0 |
|
Molybdenum, Mo |
5.0-9.0 |
|
Aluminum, Al |
1.70-2.50 |
|
Titanium, Ti |
1.50-3.0 |
|
Iron, Fe |
1.0 |
|
Silicon, Si |
0.50 |
|
Manganese, Mn |
0.50 |
|
Copper, Cu |
0.20 |
|
Carbon, C |
0.070 |
|
Zirconium, Zr |
0.060 |
|
Sulfur, S |
0.015 |
|
Boron, B |
0.0050 |
Physical Properties
The following table shows the physical properties of Nimonic PK33™.
|
Properties |
Metric |
Imperial |
|
Density |
8.21 g/cc |
0.297 lb/in³ |
|
Melting point |
1327°C |
2420°F |
Mechanical Properties
The mechanical properties of Nimonic PK33™ are displayed in the following table.
|
Properties |
Metric |
Imperial |
|
Tensile strength (precipitation hardened, value at room temperature) |
1150 MPa |
167000 psi |
|
Yield strength (@strain 0.200%, precipitation hardened, value at room temperature) |
750 MPa |
109000 psi |
|
Elongation at break (precipitation hardened) |
30% |
30% |
Thermal Properties
The thermal properties of Nimonic PK33™ are given in the following table.
|
Properties |
Metric |
Imperial |
|
Thermal expansion co-efficient (@20-100°C/68-212°F) |
12.1 µm/m°C |
6.72 µin/in°F |
|
Thermal conductivity |
11.3 W/mK |
78.4 BTU in/hr.ft².°F |
Fabrication and Heat Treatment
Annealing
Nimonic PK33™ is annealed at 1107°C (2025°F) and then air cooled.
Cold Working
Standard tooling methods are used for cold working Nimonic PK33™. Usage of plain carbon steels is not recommended as they may produce galling. Galling can be reduced by the usage of soft die materials and heavy duty lubricants.
Welding
Welding techniques recommended for Nimonic PK33™ include gas-tungsten arc welding, gas metal-arc welding, submerged-arc welding and shielded metal-arc welding. Usage of a matching alloy filler metal is recommended for the welding process and an alloy rich in Ni, Co, Cr, Mo is used during the absence of a matching filler metal.
Forming
Conventional methods are used for forming Nimonic PK33™ that has good ductility . Heavy-duty lubricants can be used for forming Nimonic PK33™. Powerful equipment is recommended for forming this alloy as it is stronger than the commonly available steels.
Machinability
Nimonic PK33™ is machined by conventional machining methods. This alloy has higher levels of gunniness and strength and is work-hardened during the machining process. Tooling and usage of a heavy duty machining equipment during the machining process minimize work-hardening or chatter of this alloy before the cutting process. Heavy lubricants are suitable for boring, tapping, drilling or broaching, and coolants that are water-based are recommended for high- speed operations like milling, grinding or turning.
Heat Treatment
Nimonic PK33™ is solution annealed at 1327°C (2025°F) and then cooled. This is followed by heat treating the alloy under 849°C (1560°F) for 4 hours and finally cooling the alloy in air.
Hardening
Nimonic PK33™ can be hardened by thermal treatment or cold working.
Applications
Nimonic PK33™ can be used at elevated temperatures in applications like enclosures for furnace hot sections used in industries or gas turbine hot sections.