Topics CoveredIntroductionChemical CompositionPhysical PropertiesMechanical PropertiesOther DesignationsFabrication and Heat Treatment Machinability Forming Welding Heat Treatment Forging Hot Working Cold Working Annealing Aging HardeningApplications
Super alloys have good creep and oxidation resistance. They can function at very high temperatures and severe mechanical stress, and also where high surface stability is required. They can be strengthened by solid-solution hardening, work hardening, and precipitation hardening. They contain a number of elements in a variety of combinations to achieve the desired result.
Allvac 718™ is a nickel-chromium alloy having high corrosion resistance, temperature resistance and strength. The datasheet given below gives more details about Allvac 718™.
The following table shows the chemical composition of Allvac 718™.
The physical properties of Allvac 718™ are highlighted in the following table.
The mechanical properties of Allvac 718™ are displayed in the following table.
|Yield strength (@ strain 0.200%)
|Elongation at break
|Reduction of area
|Hardness, Brinell (estimated from Rockwell C value for Brinell test with 3000 kg load/10 mm diameter ball)
|Hardness, Knoop (estimated from Rockwell C value)
|Hardness, Rockwell C
|Hardness, Vickers (estimated from Rockwell C value)
Other designations that are equivalent to Allvac 718™ are included in the following table.
||GE B50 TF14
||GE B50 TF69
Fabrication and Heat Treatment
Allvac 718™ can be machined using conventional machining methods which are used for iron-based alloys. Machining operations are performed using commercial coolants. High -speed operations such as grinding, milling or turning, are performed using water-based coolants.
Allvac 718™ can be formed using all conventional techniques
Allvac 718™ is welded using gas-tungsten arc welding, shielded metal-arc welding, gas metal-arc welding, and submerged-arc welding methods
Allvac 718™ is heat treated by annealing at 1038°C (1900°F) followed by cooling.
Allvac 718™ is forged at 927 to 1122°C (1700 to 2050°F).
Allvac 718™ is hot worked at 899°C to 1122°C (1650 to 2050°F). If the temperature falls below 899°C (1650°F), this alloy must be reheated again.
Allvac 718™ can be cold worked using standard tooling.
Allvac 718™ is annealed at 1038°C (1900°F) followed by cooling.
Allvac 718™ has two different types aging heat treatments. In the first type of treatment, this alloy is aged at 719°C (1325°F) for 8 h followed by cooling in a furnace. It is then held at that temperature for 10 h followed by again cooling in air in order to achieve good rupture properties and highest room temperature strength. In the second type of treatment, this alloy is aged at 760°C (1400°F) followed by cooling in a furnace. It is then held at that temperature for 10 h followed by cooling in air again to achieve good transverse ductility, especially in heavy sections.
Allvac 718™ can be hardened by cold working.
Allvac 718™ is mainly used in cryogenic storage tanks and gas turbine hot section components.