Nov 12 2012
Topics Covered
IntroductionChemical CompositionPhysical PropertiesMechanical PropertiesThermal PropertiesOther DesignationsFabrication and Heat Treatment Machinability Forming Welding Heat Treatment Forging Cold Working Annealing AgingApplications
Introduction
Super alloys or high performance alloys have an ability to function at very high temperatures and mechanical stress, and also where high surface stability is required. They have good creep and oxidation resistance, and can be produced in a variety of shapes. They can be strengthened by solid-solution hardening, work hardening, and precipitation hardening.
Super alloys consist of a number of elements in a variety of combinations to achieve the desired result. They are further classified into three groups such as cobalt-based, nickel-based, and iron-based alloys.
Discaloy™ is an age-hardenable alloy containing chromium and nickel as the principle alloying element. The following datasheet gives an overview of Discaloy™.
Chemical Composition
The chemical composition of Discaloy™ is outlined in the following table.
| Element |
Content (%) |
| Nickel, Ni |
24-28 |
| Chromium, Cr |
13-15 |
| Molybdenum, Mo |
2.5-3.5 |
| Titanium, Ti |
1.5-2 |
| Manganese, Mg |
1.5 max |
| Silicon, Si |
1 max |
| Copper, Cu |
0.5 max |
| Aluminum, Al |
0.35 |
| Carbon, C |
0.08 |
| Phosphorus,P |
0.04 max |
| Sulfur, S |
0.03 max |
| Boron, B |
0.01-0.001 |
Physical Properties
The following table shows the physical properties of Discaloy™
| Properties |
Metric |
Imperial |
| Density |
7.7-8.03 g/cm³ |
0.278-0.290lb/in³ |
| Melting point |
1455°C |
2650°F |
Mechanical Properties
The mechanical properties of Discaloy™ are displayed in the following table.
| Properties |
Metric |
Imperial |
| Tensile strength |
1158 MPa |
167954 psi |
| Yield strength |
1034 MPa |
149969 psi |
| Elastic modulus |
190-210 GPa |
27557-30458 ksi |
| Poisson's ratio |
0.27-0.30 |
0.27-0.30 |
| Elongation |
15% |
15% |
| Reduction |
53% |
53% |
| Hardness |
335 |
335 |
Thermal Properties
The thermal properties of Discaloy™ are given in the following table.
| Properties |
Conditions |
| T (ºC) |
Treatment |
| Thermal conductivity |
42.7 W/mK |
100 |
- |
Other Designations
Other designations that are equivalent to Discaloy™ include:
- AMS 5733
- ASTM A453 (662)
- ASTM A638 (662)
Fabrication and Heat Treatment
Machinability
Discaloy™ is machined using conventional machining methods which are used for iron-based alloys. It has machining properties similar to that of austenitic stainless steels. Work-hardening of this alloy can be reduced by using a heavy duty machining equipment and tooling. Water-based coolants are used in machining operations.
Forming
Discaloy™ is formed using conventional techniques.
Welding
Discaloy™ is welded using gas tungsten arc welding, shielded metal-arc welding, and metal-arc welding methods. Submerged-arc welding is not preferred for this alloy. Slag should be completely removed using a wire brush after completing this process.
Heat Treatment
Discaloy™ is heat treated by annealing and cold working.
Forging
Discaloy™ has good forgeability.
Cold Working
Discaloy™ can be cold worked using standard tooling. Soft die materials such as zinc alloys and bronze are used to produce good finishing and reduce galling problems.
Annealing
Discaloy™ is annealed at 1010°C (1850°F) for 2 h followed by quenching in oil.
Aging
Discaloy™ is aged by annealing at 1010°C (1850°F) for 2 h followed by quenching in oil, and then at 733°C (1350°F) for 20 h followed by cooling in air, and finally at 649°C (1200°F) for 20 h followed by cooling in air.
Applications
Discaloy™ is mainly used in gas turbine hot section components.