Hangbo Alloy Group
Shanghai · Est. 2012
N08840 technical guide: nominal chemical composition, mechanical and physical properties, corrosion resistance, welding, product forms and ASTM standards...
Incoloy 840 (UNS N08840) is a nickel-iron-chromium alloy. Low-carbon 800-type for emission-control hardware. Good oxidation & thermal-fatigue 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 Incoloy 840 for a project.
Incoloy 840 belongs to the nickel-iron-chromium alloy class of materials. It is low-carbon 800-type for emission-control hardware. It is good oxidation & thermal-fatigue resistance. It is weld-sensitization resistant.
Nominal (wt%) composition of Incoloy 840 (UNS N08840):
| Element | Composition (wt%) |
|---|---|
| Nickel (Ni) | 30.5 – 34.0 |
| Chromium (Cr) | 20.5 – 23.0 |
| Iron (Fe) | Balance |
| Titanium (Ti) | 0.6 – 1.2 |
| Aluminium (Al) | 0.3 – 0.8 |
| Carbon (C) | 0.03 – 0.08 |
| Manganese (Mn) | ≤ 1.0 |
| Silicon (Si) | ≤ 1.0 |
| Sulphur (S) | ≤ 0.015 |
| Copper (Cu) | ≤ 0.75 |
Typical physical properties:
| Property | Value |
|---|---|
| Density | 7.94 g/cm³ |
| Melting Range | 1300 – 1400 °C |
| Thermal Expansion (20–1000 °C) | 15.5 µm/m·K |
| Thermal Conductivity (100 °C) | 12.0 W/m·K |
| Modulus of Elasticity | 195 GPa |
Typical room-temperature mechanical properties (annealed / specified condition unless noted):
| Property | Typical Value |
|---|---|
| Tensile Strength (Rm) | 560 MPa (81 ksi) |
| Yield Strength, 0.2% (Rp0.2) | 240 MPa (35 ksi) |
| Elongation in 50 mm | 40% |
| Hardness (Rockwell B) | 75 – 88 HRB |
| Property | Value |
|---|---|
| Service temperature | Up to 900 °C |
| Sensitization-resistant (low C) | 0.03 – 0.08 % C |
840 is a low-carbon variant of the 800 family optimised for automotive emission-control hardware. The low carbon plus titanium/aluminium gives good high-temperature oxidation and thermal-fatigue resistance and avoids sensitised welds in thin-wall tubing.
Welded with matching or 800H-type fillers; the low carbon makes it resistant to weld sensitising, so post-weld heat treatment is rarely needed for emission-control fabrications.
The grade is supplied to the following common specifications:
| Standard | Product Form / Scope |
|---|---|
| ASTM B407 | Seamless pipe & tube |
| ASTM B408 | Bar & wire |
| ASTM B409 | Plate, sheet & strip |
Standards & References. Specifications cited on this page; confirm current revisions with the issuing body.
General references: Nickel Institute · AMPP (corrosion) · SAE International · ASTM International
840 is a low-carbon Ni-Fe-Cr alloy in the 800 family tuned for automotive emission-control parts. Compared with 802, the carbon is much lower (0.03–0.08 %) so it resists weld sensitising while keeping good oxidation and thermal-fatigue resistance to about 900 °C.
Annealed: ≈ 560 MPa tensile, ≈ 240 MPa yield, 40 % elongation, 75–88 HRB.
840 has a lower, tighter carbon range (0.03–0.08 %) aimed at thin-wall welded emission-control tubing, whereas 800H carries controlled higher carbon + Ti/Al for creep strength.
Yes, with 800H-type fillers; the low carbon avoids HAZ sensitisation, so post-weld heat treatment is usually unnecessary.
Exhaust manifolds, EGR coolers, emission-control tubing and after-treatment housings, plus thin-wall high-temperature tubing.
ASTM B407 (seamless pipe/tube), B408 (bar/wire), B409 (plate/sheet/strip).
As a dedicated nickel alloy manufacturer serving power generation, chemical processing, 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.