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Alloy 625 Inconel Supplied in Sheet, Coil, Bar & Plate - AMS 5599, 5666, UNS N06625


Inconel® 625 is a nickel-based superalloy with excellent resistance to oxidation and corrosion, in conditions ranging from jet engine propulsion systems to chemical processing of oxidizing and reducing acids. The nickel-chromium matrix of Inconel 625 is reinforced by the addition of molybdenum and niobium, which is alloyed through solid solution strengthening, and this allows it to maintain high strength and toughness at temperatures ranging from cryogenic up to 2000°F (1093°C). It is non-magnetic, austenitic, and displays high tensile strength, fabricability, and brazeability. Due to its high nickel content, this alloy is nearly immune to chloride ion stress-corrosion cracking and pitting, which is commonly found in metals in seawater applications like heat exchangers, fasteners, and cable sheathing.

Standard Inventory Specifications

625 Plate, Sheet, and Coil

  • AMS 5599
  • ASTM B 443 Gr 1
  • ASME SB 443 Gr 1

625 Bar

  • AMS 5666
  • ASTM B 446

Other industry standards we comply with

  • UNS N06625
  • UNS N06626
  • DFARS Compliant
  • RR SABRe Edition 2
  • GE-S400/1000
  • EMS95377
  • EN 2.4856
  • EN 10204

Common Trade Names

Alloy 625, Nickel 625, Inconel 625 (® Special Metals), Haynes 625 (® Haynes International)

Inventory Size Range

  • Sheet : 0.016" - 0.165"
  • Bar : 0.375" - 7.000"
  • Plate : 0.1875" - 2.000"

Now Stocking 625-LCF (Low Cycle Fatigue);

  • This material is Vacuum Induction Melted - Electroslag Remelted, Type 1
  • Available in thicknesses from .031" nom. to .078" nom.

Please contact us for more details. The technical data provided is for information only and not for design purposes. It is not warranted or guaranteed.

Chemical Composition

Chemical Composition

Element Percent by Weight
Carbon 0.010 maximum
Manganese 0.50 maximum
Phosphorus 0.015 maximum
Sulfur 0.015 maximum
Silicon 0.50 maximum
Chromium 20.00 - 23.00
Nickel Balance
Molybdenum 8.00 - 10.00
Columbium 3.15 - 4.15
Titanium 0.40 maximum
Aluminum 0.40 maximum
Tantalum 0.05 maximum
Iron 5.00 maximum

 

Physical Properties

  • Density: 0.303 lb/in3 (8.44 g/cm3
  • Specific Gravity: 8.44
  • Melting Range: 2350 - 2460°F (1280 - 1350°C)
  • Specific Heat: 0.098 Btu/lb x °F (410 Joules/kg x °K)
  • Magnetic Permeability (75°F, 200 oersted): 1.0006

Thermal Conductivity

Temperature Range Linear Coefficients of Thermal Expansion1 · 10-6 Thermal Conductivity2 3
°C °F /°C /°F W/m·K Btu/(hr/ft²/in/°F)
-157 -250 - - 7.3 4.2
-129 -200 - - 7.4 4.3
-73 -100 - - 8.3 4.8
-18 0 - - 9.2 5.3
21 70 - - 9.9 5.7
38 100 - - 10.0 5.8
93 200 12.8 7.1 10.7 6.3
204 400 13.1 7.3 12.6 7.3
316 600 13.3 7.4 14.2 8.2
427 800 13.7 7.6 15.7 9.1
538 1000 14.0 7.8 17.5 10.1
649 1200 14.8 8.2 19.0 11.0
760 1400 15.3 8.5 20.8 12.0
871 1600 15.8 8.8 22.8 13.2
927 1700 16.2 9.0 - -
982 1800 - - 25.3 14.6
  1. Average coefficient from 70°F (21°C) to temperature shown
  2. Measurements made at Battelle Memorial Institute
  3. Material annealed 2100°F (1149°C)

Electrical Resistivity

Temperature microhm-cm
°C °F
21 70 128.9
38 100 129.6
93 200 131.9
204 400 133.9
316 600 134.9
427 800 135.9
538 1000 137.9
649 1200 137.9
760 1400 136.9
871 1600 135.9
982 1800 134.9
1093 2000 133.9

Mechanical Properties and Yield Strength

Mechanical Properties and Yield Strength of Alloy 625

Temperature 0.2% Yield Strength Ultimate Tensile Strength Elongation Percent
°F °C psi MPa psi MPa
1920 1065 63,000 430 136,000 940 51.5

The technical data provided is for information only and not for design purposes. It is not warranted or guaranteed.

A brief history of Inconel® 625

The patent for Inconel 625 was issued on December 8th, 1964 after long years of research into a Ni-Cr-Mo-Nb alloy (Nickel Chromium Molybdenum Niobium). It is a so-called “superalloy”, because of its ability to withstand high temperatures, stress and corrosion.

Originally developed for high pressure steam lines in power plants, it quickly became apparent that alloy 625 could handle extreme corrosion and oxidation from harsh environments. Molybdenum, chromium, and niobium give this alloy additional creep strength from stressors like high temperatures (maintaining its resistance to oxidation at temperatures up to 1800°F) and other harsh conditions that could deform less resistant alloys over time. Thermal strengthening through heat treatment improves the yield strength, but due to embrittlement at high temperatures over extended time periods, this alloy is best used in lower temperature applications where its corrosion resistance shines.

Common applications

Offshore wellheads using alloy 625 Even though researchers initially touted its creep strength at high temperatures, it was also shown that alloy 625 could remain nearly corrosion free at ambient to low temperature elevations, like seawater environments or chemical processing of acids and salts. Marine heat exchangers commonly use 625, to isolate corrosive seawater to materials that can endure them, such as 625 based plate and shell and tube heat exchangers.

It is nearly immune to chloride-ion induced stress cracking, by virtue of its high nickel content, and has been used in propellers and propulsion systems as well as wires used in cable sheathing in marine environments. In addition to saltwater corrosion resistance, the high ductility of 625 makes it ideal for fasteners like hex bolts in underwater environments.

Because of its ease of weldability, Inconel 625 has been used in weld overlays (weld overlay cladding) to improve the strength and corrosion resistance of base metals, such as those found in boiler tubes or petrochemical equipment like wellheads. Cheaper, thick layers of base materials like steel alloys can be weld cladded with alloy 625 even at economical dilutions with the right technique, giving much needed strength and protection against corrosion to these parts.

It is also used in waste-to-energy boilers, where refuse-derived-fuel is used to power steam generators with refuse boilers. Inconel 625 replaced heat resistant materials like ceramic tiles for corrosion protection, primarily as welded cladding and composite tubes, which significantly lowered the cost of maintenance on corroded refractory. By the late 1990s, this alloy was widely seen as the most corrosion resistant alloy at conditions caused by waste combustion.

Vacuum Processing of Inconel 625

N06625 vs. N06626 - one method of processing alloy 625 is through Vacuum Induction Melting (VIM), which uses a strong electric current to melt the alloy in a vacuum. Through careful control of the melting process, manufacturers can produce a more uniform microstructure with a fine grain size. Inconel 625 that has undergone this process is known as 625 LCF (Low Cycle Fatigue) – it has better thermal stability and improved resistance to mechanical fatigue. Bellows are an excellent example of a structure that undergoes cyclic temperature conditions and can be improved by the use of 625-LCF.

United Performance Metals is a supplier of both N06625 and N06626 in varying thicknesses.

Modern Innovations with Inconel 625

While Inconel 718 remains the most successful super alloy among the Inconel family (also a direct result of 625’s original research), this alloy is still finding new ways to impress the engineering world.

Solar collector tubes often use Inconel 625 for molten saltSolar power stations that use super-heated salt (potassium and sodium nitrate), have used Inconel 625 in the seamless tubing of the solar receivers. Solar Two was a collaborative project between US government and industry organizations that ran from 1996 to 1999, and provided up to 10MW of power. Molten salt, which is highly corrosive at temperatures found in these plants, powered a steam generator, and Inconel 625 tubing was used to push the molten salt through the central solar collector. Solar Tres (Solar III), a followup project under construction in Spain, will also use molten salt with Inconel 625 tubing in the collectors.

The automotive industry has used Inconel 625 in exhaust manifolds and other components, as a lightweight alternative to steel with exceptional weldability and corrosion resistance against environments like saltwater air and road salts. Tesla, perhaps learning from the experiences of SpaceX, used Inconel to replace steel in the contactors for the Model S main battery pack, increasing maximum output from 1300 amps to 1500 amps.

As a global distributor and longtime supplier of alloy 625 and 625 LCF, United Performance Metals can help meet your demand for high quality alloys. Call us today or request a quote here.


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