Nov 23 2012
Topics Covered
IntroductionChemical CompositionPhysical PropertiesMechanical PropertiesThermal PropertiesFabrication and Heat Treatment Machinability Forming Welding Heat Treatment Forging Hot Working Cold Working Annealing HardeningApplications
Introduction
Super alloys or high performance alloys have high creep and oxidation resistance. They can be strengthened by solid-solution hardening, work hardening, and precipitation hardening. They can be used in environments with high temperatures and mechanical stress, and also where high surface stability is required. There are three groups of alloys such as cobalt-based, nickel-based, and iron-based alloys.
Incoloy(r) alloy 925™ is a precipitation-hardenable nickel-iron-chromium alloy. It can be age-hardened by adding aluminum and titanium. On the other hand, copper and molybdenum are added to increase its resistance to corrosive media. The datasheet given below discusses about Incoloy(r) alloy 925™ in detail.
Chemical Composition
The following table shows the chemical composition of Incoloy(r) alloy 925™.
| Elements |
Content (%) |
| Nickel, Ni |
44 |
| Iron, Fe |
28 |
| Chromium, Cr |
21 |
| Molybdenum, Mo |
3 |
| Titanium, Ti |
2.1 |
| Copper, Cu |
1.8 |
| Aluminum, Al |
0.3 |
| Carbon, C |
0.01 |
Physical Properties
The physical properties of Incoloy(r) alloy 925™ are given in the following table.
| Properties |
Metric |
Imperial |
| Density |
8.05 g/cm³ |
0.291 lb/in³ |
| Melting point |
1343°C |
2450°F |
Mechanical Properties
The mechanical properties of Incoloy(r) alloy 925™ are outlined in the following table.
| Properties |
Metric |
Imperial |
| Tensile strength (precipitation hardened, value at room temperature) |
1210 MPa |
175000 psi |
| Tensile strength (@ 550°C/1020°F, precipitation hardened prior to test) |
970 MPa |
141000 psi |
| Yield strength (@ strain 0.200%, precipitation hardened. value at room temperature) |
810 MPa |
117000 psi |
| Yield strength (@ strain 0.200%, temperature 550°C/1020°F, precipitation hardened prior to test) |
700 MPa |
102000 psi |
| Poisson's ratio |
0.281 |
0.281 |
| Elongation at break (precipitation hardened) |
24% |
24% |
Thermal Properties
The thermal properties of Incoloy(r) alloy 925™ are displayed in the following table.
| Properties |
Metric |
Imperial |
| Thermal expansion co-efficient (@ 20-100°C/68-212°F) |
13.2 µm/m°C |
7.33 µin/in°F |
Fabrication and Heat Treatment
Machinability
Incoloy(r) alloy 925™ can be machined using conventional machining methods which are used for iron based alloys. Tooling and heavy duty machining equipments are used to reduce work-hardening of this alloy. Machining operations can be performed by using commercial coolants. High speed operations such as grinding, turning, or milling, are usually performed using water-based coolants.
Forming
Incoloy(r) alloy 925™ can be easily formed using all conventional techniques. Heavy-duty lubricants are used while cold forming.
Welding
Shielded metal-arc welding, gas metal-arc welding, gas-tungsten arc welding, and submerged-arc welding methods are preferred for welding Incoloy(r) alloy 925 ™.
Heat Treatment
Incoloy(r) alloy 925™ is heat treated by annealing at 983 to 1038°C (1800 to 1900°F) followed by cooling.
Forging
Forging of Incoloy(r) alloy 925™ is done at 927 to 1177°C (1700 to 2150°F).
Hot Working
Incoloy(r) alloy 925™ is hot worked at 872 to 983°C (1600 to 1800°F). Temperature should not exceed above 983°C (1800°F) in order to restore corrosion resistance of this alloy.
Cold Working
Incoloy(r) alloy 925™ 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(r) alloy 925™ is annealed at 1010°C (1850°F) for 2 h followed by air cooling.
Hardening
Incoloy(r) alloy 925™ is hardened by heat treatment and cold working.
Applications
Incoloy(r) alloy 925™ can be used in high-strength piping systems and petroleum industry.