Nov 12 2012
Topics Covered
IntroductionChemical CompositionPhysical PropertiesMechanical PropertiesThermal PropertiesOther DesignationsFabrication and Heat Treatment Forming Welding Heat Treatment Forging Cold Working Annealing AgingApplications
Introduction
Super alloys have good creep and oxidation resistance. They can be formed in different shapes, and used in environments with very high temperatures and mechanical stress, and also where high surface stability is required. They consist of a number of elements in a variety of combinations to achieve the desired result. Solid-solution hardening, work hardening, and precipitation hardening are performed to increase their strength. Cobalt-based, nickel-based, and iron-based alloys are three groups of super alloys. They all can be used at temperatures above 540°C (1000°F).
Incoloy 903™ is a nickel-cobalt alloy added with niobium to increase its oxidation resistance and strength. The following datasheet gives an overview of Incoloy 903™.
Chemical Composition
The following table shows the chemical composition of Incoloy 903™.
| Element |
Content (%) |
| Iron, Fe |
42 |
| Nickel, Ni |
38 |
| Cobalt, Co |
15 |
| Niobium, Nb |
3 |
| Titanium, Ti |
1.4 |
| Aluminum, Al |
0.9 |
Physical Properties
The physical properties of Incoloy 903™ are outlined in the following table.
| Properties |
Metric |
Imperial |
| Density |
8.25 g/cm³ |
0.298 lb/in³ |
| Melting point |
1385°C |
2525°F |
Mechanical Properties
The mechanical properties of Incoloy 903™ are displayed in the following table.
| Properties |
Metric |
Imperial |
| Tensile strength (precipitation hardened) |
1310 MPa |
190000 psi |
| Yield strength (@ strain 0.200 %, precipitation hardened) |
1100 MPa |
160000 psi |
| Elastic modulus (@ 0°C/32°F) |
146.8 GPa |
21290 ksi |
| Poisson's ratio (@ 250°C/482°F) |
0.226 |
0.226 |
| Elongation at break (precipitation hardened) |
14% |
14% |
Thermal Properties
The thermal properties of Incoloy 903™ are given in the following table.
| Properties |
Metric |
Imperial |
| Thermal expansion co-efficient (@ 25-427°C/77-801°F) |
7.65 µm/m°C |
4.25 µin/in°F |
| Thermal conductivity |
16.7 W/mK |
116 BTU in/hr.ft².°F |
Other Designations
Other designation equivalent to Incoloy 903™ includes AMS 5803.
Fabrication and Heat Treatment
Forming
Incoloy 903™ can be formed using all conventional techniques. Heavy-duty lubricants are required during cold forming.
Welding
Incoloy 903™ can be welded using gas metal-arc welding, gas-tungsten arc welding, submerged-arc welding, and shielded metal-arc welding methods.
Heat Treatment
Incoloy 903™ is heat treated at 844°C (1550°F) for 1 hr. It is then quenched in water and aged at 719°C (1325°F) for 8 h followed by cooling. It is again aged at 622°C (1150°F) for 8 h followed by cooling in air.
Forging
Forging of Incoloy 903™ is done at 983 to 1205°C (1800 to 2200°F).
Cold Working
Incoloy 903™ can be cold worked using standard tooling. Soft die materials such as zinc alloys and bronze, are used to produce good finishing and avoid galling problems.
Annealing
Incoloy 903™ can be annealed at 844°C (1550°F) for 1 hr.
Aging
Optimum properties of Incoloy 903™ can be developed in aged conditions.
Applications
Incoloy 903™ is primarily used in gas turbine hot section components.