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.

  • Image: Coil
    Coil
  • Image: Sheet
    Sheet
  • Image: Plate
    Plate

Designation / Standard

Nippon Yakin Grade ASTM B409 EN JIS G4902
NAS 800 UNS N08800 1.4876 NCF 800

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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

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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

 

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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

Image: High-Temperature Strength

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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.

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