Super Alloy Pyromet 625 (UNS N06625)

Topics Covered

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

Introduction

Pyromet 625 alloy is a nonmagnetic, corrosion- and oxidation-resistant, nickel-base alloy with outstanding strength and toughness in high temperatures up to 1093°C (2000°F). The alloy has excellent stress-corrosion cracking resistance to chloride ions and fatigue strength.

The following section will provide an overview of Pyromet 625 alloy.

Chemical Composition

The chemical composition of Pyromet 625 alloy is outlined in the following table.

Element Content (%)
Chromium,Cr 20-23
Molybdenum, Mo 8-10
Iron, Fe 5
Niobium, Ni 3.15-4.15
Cobalt, Co 1
Silicon, Si 0.5
Manganese, Mn 0.5
Titanium, Ti 0.4
Aluminum, Al 0.4
Carbon, C 0.1
Phosphorus, P 0.015
Sulfur, S 0.015

Physical Properties

The following table shows the physical properties of Pyromet 625 alloy.

Properties Metric Imperial
Density 8.44 g/cm3 0.305 lb/in3
Melting point 1329°C 2425°F

Mechanical Properties

The mechanical properties of Pyromet 625 alloy are displayed in the following table.

Properties Metric Imperial
Tensile strength (annealed) 880 MPa 128000 psi
Yield strength (annealed) 460 MPa 66700 psi
Elongation at break (annealed prior to test) 50% 50%

Thermal Properties

The thermal properties of Pyromet 625 alloy are given in the following table

Properties Metric Imperial
Thermal expansion co-efficient (@20-100°C/68-212°F) 12.8 µm/m°C 7.11 µin/in°F
Thermal conductivity 9.8 W/mK 68 BTU.in/hrft².°F

Fabrication and Heat Treatment

Machinability

Pyromet 625 alloy can be machined by conventional means. However, rigid tooling is required to prevent chatter and work hardening in front of the tool edge.

Welding

The alloy can be readily welded using alloy filler metal.

Heat Treatment

The alloy is heat treated at 1177°C (2150°F) and then air cooled.

Forging

Hot forging can be carried out by heating the alloy at 1149 to 1177°C (2100 to 2150°F).

Hot Working

The alloy may be hot worked at 1177°C (2150°F).

Cold Working

The alloy can be cold formed by conventional means and tooling.

Annealing

Annealing of Pyromet 625 alloy can be performed 982 to 1093°C (1800 to 2000°F) and air cooled.

Hardening

The strength of the alloy can be improved by cold working.

Other Designations

Other designations that are equivalent to Pyromet 625 alloy include the following:

  • MIL E-21562
  • GE B50TF133
  • DIN 2.4856
  • ASTM B366
  • ASTM B443
  • ASTM B444
  • ASTM B446
  • ASTM B704
  • ASTM B705
  • AMS 5581
  • AMS 5599
  • AMS 5666
  • AMS 5837
  • AMS 5879

Applications

The following are the list of applications of Pyromet 625 alloy:

  • Heat shields
  • Furnace hardware
  • Gas turbine engine ducting
  • Chemical plant hardware and special seawater applications
  • Combustion liners and spray bars
  • Aerospace and marine engineering.

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