Inconel 725 | UNS N07725 | FMC Spec M40504 | NACE MR-0175 | ISO 15156 | ASTM B 805 | ASME Code Case 2217 | HA91

INCONEL alloy 725 (UNS N07725) is a nickelchromium- molybdenum-niobium alloy that is highly resistant to corrosion and is age hardenable for extremely high strength. It has essentially the same corrosion resistance as INCONEL alloy 625, which is widely used in a broad range of severely corrosive environments. The strength of age-hardened INCONEL alloy 725 is of the order of twice that of annealed alloy 625. Because the strength of alloy 725 is developed by heat treatment, not by cold work, ductility and toughness remain high. Also, strength can be imparted to large or non-uniform sections that cannot be strengthened by cold work.

The chemical composition of INCONEL alloy 725 is given. High levels of nickel and chromium provide corrosion resistance in reducing and oxidizing environments. The substantial molybdenum content enhances resistance to reducing media and provides a high degree of resistance to pitting and crevice corrosion. Additionally, the combination of elements makes the alloy resistant to hydrogen embrittlement and stresscorrosion cracking. The properties of INCONEL alloy 725 are useful for a range of applications that require outstanding corrosion resistance along with high strength. The alloy is used for hangers, landing nipples, side pocket mandrels and polished bore  eceptacles in sour gas service, where it resists the effects of hydrogen sulfide, chlorides and carbon dioxide. The alloy is also attractive for high strength fasteners in marine applications, where it resists corrosion, pitting and crevice attack in sea water.

Chemical Composition

Nickel……………………………………………………………….55.0-59.0
Chromium…………………………………………………………19.0-22.5
Molybdenum…………………………………………………………7.0-9.5
Niobium……………………………………………………………..2.75-4.0
Titanium……………………………………………………………….1.0-1.7
Aluminum…………………………………………………………0.35 max.
Carbon…………………………………………………………….0.03 max.
Manganese………………………………………………………0.35 max.
Silicon……………………………………………………………..0.20 max.
Phosphorus…………………………………………………….0.015 max.
Sulfur……………………………………………………………..0.010 max.
Iron……………………………………………………………………Balance*
*Reference to the ‘balance’ of a composition does not guarantee this is exclusively of the element mentioned but that it predominates and others are present only in minimal quantities.

Physical Properties

Some representative physical properties of INCONEL alloy 725 are given. Values for thermal expansion and electrical resistivity over a range of temperatures are listed. Resistivity at elevated temperature was calculated from observed percent change in the room-temperature value. Modulus of elasticity, determined dynamically. All values for physical properties are for material in the age-hardened condition.

Density,
lb/in3……………………………………………………….0.300
g/cm3………………………………………………………..8.31
Melting Range,
°F……………………………………………………………..2320-2449
°C…………………………………………………………….1271-1343
Permeability at 200 oersted (15.9 kA/m)……………….<1.001
Young’s Modulus (70°F),
ksi x 103…………………………………………………….29.6
GPa…………………………………………………………..204
Shear Modulus (70°F),
ksi x 103…………………………………………………….11.3
GPa……………………………………………………………78
Poisson’s Ratio (70°F)………………………………………….0.31

Specifications

ASTM B 805,
HA91,
ASME Code Case 2217
UNS N07725
FMC Spec M40504
NACE MR-0175/ ISO 15156
Inconel 725 (trademark)

 

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