Jan 2 2013
Topics Covered
IntroductionChemical CompositionPhysical PropertiesThermal PropertiesFabrication and Heat Treatment Annealing Cold Working Welding Forging Forming Machinability Aging Heat TreatmentApplications
Introduction
Super alloys or high performance alloys are available in a variety of shapes and contain elements in different combinations to obtain a specific result. These alloys are of three types that include iron-based, cobalt-based and nickel-based alloys.
Super alloys have good oxidation and creep resistance and can be strengthened by precipitation hardening, solid-solution hardening and work hardening methods. They can also function under high mechanical stress and high temperatures and also in places that require high surface stability.
The following datasheet provides an overview of Udimet 720™.
Chemical Composition
The chemical composition of Udimet 720™ is outlined in the following table.
| Element |
Content (%) |
| Nickel, Ni |
55.16-59.705 |
| Chromium, Cr |
15.5-16.5 |
| Cobalt, Co |
14.0-15.5 |
| Titanium, Ti |
4.75-5.25 |
| Molybdenum, Mo |
2.75-3.25 |
| Aluminum, Al |
2.25-2.75 |
| Tungsten, W |
1.00-1.50 |
| Zirconium, Zr |
0.0250-0.0500 |
| Boron, B |
0.0100-0.0200 |
| Carbon, C |
0.0100-0.0200 |
Physical Properties
The following table shows the physical properties of Udimet 720™.
| Properties |
Metric |
Imperial |
| Density |
8.08 g/cm³ |
0.292 lb/in³ |
| Melting point |
1371°C |
2500°F |
Thermal Properties
The thermal properties of Udimet 720™ are given in the following table.
| Properties |
Metric |
Imperial |
| Thermal expansion co-efficient (@93°C/199°F) |
12.24 µm/m°C |
6.800 µin/in°F |
Fabrication and Heat Treatment
Annealing
Udimet 720™ is annealed at 1121°C (2050°F) and then cooled in air in a rapid manner.
Cold Working
Standard tooling methods are used for cold working Udimet 720™. 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. Tooling is recommended in the cold working process to allow liberal radii and clearances.
Welding
Welding processes recommended for Udimet 720™ include gas-tungsten arc welding, gas metal-arc welding and shielded metal-arc welding. Submerged-arc welding is not recommended as cracks may develop due to the high heat input. This alloy can be welded by the commonly used welding procedures and the welding surfaces should be free from paint, crayon markings or oil.
Forging
Udimet 720™ is capable of being forged as it is ductile.
Forming
Conventional methods are used to readily form Udimet 720™ that has good ductility. To obtain good forming results a powerful equipment is used along with heavy-duty lubricants. Usage of heavy-duty lubricants is recommended during the cold forming process of this alloy. After the forming process all traces of the lubricant should be cleaned to prevent embrittlement of this alloy at high temperatures.
Machinability
Udimet 720™ can be machined by conventional machining methods and contains higher strength, gumminess and work-hardening qualities. Work-hardening of the alloy before the cutting process and chatter can be minimized by tooling and a heavy duty machining equipment. Usage of water-base coolants is preferred for milling, turning or grinding. Usage of heavy lubricants is preferred for boring, drilling, broaching or tapping operations.
Aging
Udimet 720™ is treated under four different temperatures to be air-hardened.
- Heat for 2 h at 1113°C (2035°F) and cool in air.
- Heat for 4 h at 1079°C (1975F) and oil quench.
- Heat for 24 h at 649°C (1200°F) and cool in air.
- Heat for 8 h at 760°C (1400°F) and cool in air.
Heat Treatment
Udimet 720™ can be age-hardened in the heat-treatment process.
Applications
Udimet 720™ is used for gas turbine hot section components.