Heat Resistant Alloys
NAS 800 (UNS N08800), comparable to Incoloy® 800 Alloy
A high nickel-content heat-resistant steel, NAS 800 (NCF 800, UNS N08800), comparable to Incoloy® 800 Alloy, provides superior strength, corrosion resistance and acid resistance at high temperatures and is compositionally close to austenitic stainless steels. It was developed as an alloy with properties comparable to Inconel®. Nippon Yakin supplies this product in plate, sheet and strip forms.
Coil
Sheet
Plate
Chemical Composition
JIS G4902 / NCF 800
| C | Si | Mn | P | S | Ni | Cr | Cu | Al | Ti | Fe | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | 30.00 | 19.00 | ― | 0.15 | 0.15 | ― |
| Max | 0.10 | 1.00 | 1.50 | 0.030 | 0.015 | 35.00 | 23.00 | 0.75 | 0.60 | 0.60 | Balance |
ASTM B409 / UNS N08800
| C | Si | Mn | P | S | Ni | Cr | Cu | Al | Ti | Fe | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | 30.0 | 19.0 | ― | 0.15 | 0.15 | 39.5 |
| Max | 0.10 | 1.0 | 1.5 | ― | 0.015 | 35.0 | 23.0 | 0.75 | 0.60 | 0.60 | ― |
EN10095 / 1.4876
| C | Si | Mn | P | S | Ni | Cr | Cu | Al | Ti | Fe | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | 30.00 | 19.00 | ― | 0.15 | 0.15 | ― |
| Max | 0.12 | 1.00 | 2.00 | 0.030 | 0.015 | 34.00 | 23.00 | ― | 0.60 | 0.60 | ― |
Physical Properties
| Specific heat (J/kg･K) | 460 | |
| Specific resistivity (μΩ･cm) | 99 | |
| Thermal conductivity (W/m･K) | 12.6 | |
| Coefficient of thermal expansion (10-6/℃) | 25–200℃ | 15.9 |
| 25–400℃ | 16.8 | |
| 25–600℃ | 17.3 | |
| 25–800℃ | 18.1 | |
| Young's modulus (MPa) | 19.7 x 104 | |
| Curie point (℃) | -115 | |
| Ferromagnetism | None | |
| Melting point (℃) | 1357-1385 | |
Properties at High Temperatures
| Thermal conductivity (W/(m•K)) |
Coefficient of thermal expansion | Young's modulus (GPa) |
|
|---|---|---|---|
| Room temp. | 12.6 | ― | 197 |
| 100℃ | 14.1 | 14.6 | 193 |
| 200℃ | 16.1 | 15.9 | 187 |
| 300℃ | 17.8 | 16.4 | 180 |
| 400℃ | 19.3 | 16.8 | 173 |
| 500℃ | 20.6 | 17.0 | 167 |
| 600℃ | 23.2 | 17.3 | 159 |
| 700℃ | 24.4 | 17.7 | 152 |
| 800℃ | 25.1 | 18.1 | 145 |
| 900℃ | 25.9 | 18.3 | 138 |
| 1000℃ | 26.7 | 18.6 | 131 |
Mechanical Properties
Mechanical Properties at Room Temperature
JIS G4902 / NCF 800
| 0.2% Yield strength (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness | |
|---|---|---|---|---|
| (HV) | (HB) | |||
| ≥ 205 | ≥ 520 | ≥ 30 | ≤ 182 | ≤ 179 |
ASTM B409 / UNS N08800
| 0.2% Yield strength (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness | |
|---|---|---|---|---|
| (HV) | (HB) | |||
| ≥ 205 | ≥ 520 | ≥ 30 | ― | ― |
EN10095 / 1.4876
| 0.2% Yield strength (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness | |
|---|---|---|---|---|
| (HV) | (HB) | |||
| ≥ 170 | 450-680 | ≥ 30 | ― | ≤ 192 |
High-Temperature Strength
Heat Treatment
NAS 800 has an austenitic structure, and the heat treatment is similar. Typical heat treatments are as follows:
- Annealing: 980-1100℃ Rapid cooling
- Stress relief annealing: 780-870℃ Air cooling
Workability
Whether hot working or cold working, NAS 800 has a workability similar to austenitic stainless steels.
For hot working, the temperature should be between 1000 and 1230℃, though light work may be done as low as 850℃. The temperature range between 650 and 800℃ should be avoided as cracks may occur.
Although the cold workability is similar to austenitic stainless steels, work hardening tends to be slightly lower.
Weldability
Such welding techniques as TIG, MIG and shield metal arc welding can be used for NAS 800 as with standard austenitic stainless steels.
Properties at High Temperatures
Because of the high nickel and chromium content, NAS 800 resists oxidation and carburization at high temperatures. Superior to SUS 310S in resisting oxidation, NAS 800 is closer to NAS 600.
The superior heat strength is also similar to NAS 600.NAS 800 is widely used when heat resistance is required as it does not become brittle due to sigma phase precipitation during use.
While NAS 800 is generally used at temperatures below 600℃, NAS 800H / 800T are recommended when creep properties are required at higher temperatures.
Corrosion Resistance
NAS 800 has superior corrosion resistance in such oxidizing corrosive environments as nitric acid and nitric acid-sulfuric acid. It performs similarly well in sodium salt and other molten salt environments, and provides stress corrosion crack sensitivity surpassing standard austenitic stainless steels.
Applications
NAS 800 is widely used in sheathed heaters, thermocouple protection tubes, heat treatment furnaces and other high-temperature environments.
* Incoloy is a registered trademark of Special Metals Corporation.
