Super Alloy Pyromet 718 (UNS N07718)

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Fabrication and Heat Treatment
     Machinability
     Forming
     Welding
     Heat Treatment
     Forging
     Hot Working
     Cold Working
     Annealing
     Hardening
Other Designations
Applications

Introduction

Pyromet 718 is a precipitation hardenable nickel-base alloy that exhibits exceptionally high yield, tensile and creep-rupture properties at temperatures up to 704°C (1300°F). The alloy allows annealing and welding without spontaneous hardening during heating and cooling. It has excellent weldability when compared to the nickel-base superalloys.

The following section will provide an overview of Pyromet 718 alloy.

Chemical Composition

The chemical composition of Pyromet 718 alloy is outlined in the following table.

Element Content (%)
Nickel, Ni 50 - 55
Chromium, Cr 17-21
Niobium, Nb 4.75-5.5
Molybdenum, Mo 2.8-3.3
Cobalt, Co 1
Titanium, Ti 0.65-1.15
Silicon, Si 0.35
Manganese, Mn 0.35
Copper, Cu 0.3
Aluminum, Al 0.2-0.8
Carbon, C 0.08
Sulfur, S 0.015
Phosphorus, P 0.015
Boron, B 0.006
Iron, Fe Balance

Physical Properties

The following table shows the physical properties of Pyromet 718 alloy.

Properties Metric Imperial
Density 8.22 g/cm3 0.297 lb/in3
Melting point 1204-1343°C 2200-2450°F

Mechanical Properties

The mechanical properties of Pyromet 718 alloy are displayed in the following table.

Properties Metric Imperial
Tensile strength (Precipitation hardened) 1375 MPa 199400 psi
Yield strength (Precipitation hardened) 1100 MPa 160000 psi
Elongation at break (Precipitation hardened) 25% 25%

Thermal Properties

The thermal properties of Pyromet 718 alloy are given in the following table

Properties Metric Imperial
Thermal expansion co-efficient (@20-100°C/68-212°F) 13 µm/m°C 7.22 µin/in°F
Thermal conductivity 11.4 W/mK 79.1 BTU.in/hrft².°F

Fabrication and Heat Treatment

Machinability

Pyromet 718 alloy can be machined using conventional machining techniques used for iron based alloys.

Forming

This alloy has good ductility, and hence it can be formed using all conventional methods.

Welding

Pyromet 718 alloy can be welded using gas-tungsten arc welding, shielded metal arc welding, submerged-arc welding and gas metal-arc welding methods.

Heat Treatment

This alloy is age-hardenable, and can be heat-treated at (1900°F) followed by air cooling.

Forging

Forging of Pyromet 718 alloy is carried out in the range of (1700 to 2050°F).

Hot Working

This alloy can be hot-worked in the temperature ranging from (1650 to 2050°F).

Cold Working

The alloy can be cold-worked using standard tooling.

Annealing

Annealing of Pyromet 718 alloy can be performed at 1900°F followed by air cooling.

Hardening

The alloy can be hardened using cold working techniques.

Other Designations

Other designations that are equivalent to Pyromet 718 alloy include the following:

AMS 5589 ASTM B637 GE B50TF15
AMS 5590 ASTM B670 PWA 1009
AMS 5596 DIN 2.4668 PWA 1010
AMS 5597 DIN 2.4688 PWA 1033
AMS 5662 GE B14H89 RBO 170-153
AMS 5663 GE B50 TF14 SPS M275
AMS 5664 GE B50 TF69 SPS M637
AMS 5832

GE B50TF14



Applications

The following are the list of applications of Pyromet 718 alloy:

  • Gas turbines
  • Turbo pump seals
  • Spacecraft
  • Rocket motors
  • Nuclear reactors
  • Tooling

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