Hangbo Alloy Group
Shanghai · Est. 2012
N07725 technical guide: nominal chemical composition, mechanical and physical properties, corrosion resistance, welding, product forms and ASTM standards...
Inconel 725 (UNS N07725) is a precipitation-hardenable nickel-chromium alloy. 625 chemistry + Ti hardening → ~2× strength of 625. Excellent pitting & chloride SCC resistance. This guide covers its nominal chemical composition, typical mechanical and physical properties, corrosion behaviour, welding, common applications, available product forms and the ASTM standards that apply — everything a specifier needs to evaluate Inconel 725 for a project.
Inconel 725 belongs to the precipitation-hardenable nickel-chromium alloy class of materials. It is 625 chemistry + ti hardening → ~2× strength of 625. It is excellent pitting & chloride scc resistance. It is nace mr0175 sour-service qualified.
Nominal (wt%) composition of Inconel 725 (UNS N07725):
| Element | Composition (wt%) |
|---|---|
| Nickel (Ni) | ≥ 55.0 |
| Chromium (Cr) | 19.0 – 22.5 |
| Molybdenum (Mo) | 7.0 – 9.5 |
| Niobium + Tantalum (Nb+Ta) | 2.75 – 4.00 |
| Titanium (Ti) | 1.0 – 1.7 |
| Aluminium (Al) | 0.35 – 0.70 |
| Iron (Fe) | ≤ 11.0 |
| Carbon (C) | ≤ 0.03 |
| Manganese (Mn) | ≤ 0.35 |
| Silicon (Si) | ≤ 0.20 |
| Sulphur (S) | ≤ 0.010 |
| Copper (Cu) | ≤ 0.20 |
Typical physical properties:
| Property | Value |
|---|---|
| Density | 8.31 g/cm³ |
| Melting Range | 1270 – 1340 °C |
| Thermal Expansion (20–1000 °C) | 13.3 µm/m·K |
| Thermal Conductivity (100 °C) | 11.0 W/m·K |
| Electrical Resistivity | 1.10 µΩ·m |
| Modulus of Elasticity | 206 GPa |
Typical room-temperature mechanical properties (annealed / specified condition unless noted):
| Property | Typical Value |
|---|---|
| Tensile Strength (Rm), aged | 1035 MPa (150 ksi) |
| Yield Strength, 0.2% (Rp0.2), aged | 760 MPa (110 ksi) |
| Elongation in 50 mm, aged | 25% |
| Hardness (Rockwell C), aged | 30 – 40 HRC |
| Property | Value |
|---|---|
| Service temperature | Cryogenic to ≈ 540 °C |
| Stress-corrosion threshold (NaCl) | High resistance |
725 has a higher strength version of the 625 chemistry with added titanium for precipitation hardening. It delivers the same outstanding resistance to pitting, crevice corrosion and chloride stress-corrosion cracking as 625, but at roughly double the strength after ageing.
Welded with matching ERNiFeCr-2 filler. Welds are normally solution-annealed and aged to restore full strength and corrosion resistance; avoid sensitising in the 540–760 °C range without ageing.
The grade is supplied to the following common specifications:
| Standard | Product Form / Scope |
|---|---|
| ASTM B805 | Precipitation-hardenable Ni-Cr-Mo-Nb alloy bar/forgings |
| NACE MR0175 / ISO 15156 | Sour (H2S) service |
| ASTM B446 (equiv. cond.) | Bar & wire reference |
Standards & References. Specifications cited on this page; confirm current revisions with the issuing body.
General references: Nickel Institute · AMPP (corrosion) · SAE International · ASTM International
725 is a precipitation-hardenable version of the 625 chemistry with added titanium. After ageing it reaches about 1035 MPa tensile and 760 MPa yield – roughly twice the strength of annealed 625 – while keeping 625-class resistance to pitting and chloride stress-corrosion cracking.
Yes. 725 is covered by NACE MR0175 / ISO 15156 for H2S-containing (sour) service, which is why it is widely used for subsea connectors, hangers and down-hole hardware.
In the aged condition: tensile strength ≈ 1035 MPa, yield ≈ 760 MPa, elongation ≈ 25 %, hardness 30–40 HRC.
With matching ERNiFeCr-2 filler, followed by solution anneal and age to recover strength and corrosion resistance. Keep welds out of the 540–760 °C sensitising band unless aged.
Choose 725 when you need 625-level corrosion resistance at roughly double strength (fasteners, connectors, springs). Choose 625 when fabricability and moderate strength with the same corrosion profile are enough.
Round bars, forgings, seamless tubes and pipes, wire/springs and plate/sheet, supplied in the solution-annealed or fully aged condition per ASTM B805.
As a dedicated nickel alloy manufacturer serving oil & gas, marine, aerospace sectors, Hangbo Alloy Group supplies the grades discussed here across all standard product forms with full ASTM/ASME documentation and EN 10204 3.1 certification. Our material is specified for applications where corrosion resistance, high-temperature strength, and traceable quality are non-negotiable. See our production & testing facilities for more on how every heat is verified.