NAS 800H / 800T (UNS N08810 / N08811), comparable to Incoloy^® 800H Alloy

Chemical Composition

JIS G4902 / NCF 800H

	C	Si	Mn	P	S	Ni	Cr	Cu	Al	Ti	Al+Ti	Fe
Min	0.05	―	―	―	―	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 N08810

	C	Si	Mn	P	S	Ni	Cr	Cu	Al	Ti	Al+Ti	Fe
Min	0.06	―	―	―	―	30.0	19.0	―	0.15	0.15	0.85	39.5
Max	0.10	1.0	1.5	―	0.015	35.0	23.0	0.75	0.60	0.60	1.20	―

ASTM B409 / UNS N08811

	C	Si	Mn	P	S	Ni	Cr	Cu	Al	Ti	Al+Ti	Fe
Min	0.06	―	―	―	―	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	Al+Ti	Fe
Min	0.06	―	―	―	―	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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Microstructure

JIS G4902 / NCF 800H

Heat Treatment	Crystal grain size
Quench at 1100℃–1170℃	< 5

ASTM B409 / UNS N08810

Heat Treatment	Crystal grain size
≥ 1121℃	< 5

ASTM B409 / UNS N08811

Heat Treatment	Crystal grain size
≥ 1149℃	< 5

Typical microstructure of NAS 800T
Grain size number = 3

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Mechanical Properties

Mechanical Properties at Room Temperature

JIS G4902 / NCF 800H

0.2% Yield strength (N/mm2)	Tensile strength (N/mm2)	Elongation (%)	Hardness
			(HV)	(HB)
≥ 175	≥ 450	≥ 30	≤ 171	≤ 167

ASTM B409 / UNS N08810

0.2% Yield strength (N/mm2)	Tensile strength (N/mm2)	Elongation (%)	Hardness
			(HV)	(HB)
≥ 170	≥ 450	≥ 30	―	―

ASTM B409 / UNS N08811

0.2% Yield strength (N/mm2)	Tensile strength (N/mm2)	Elongation (%)	Hardness
			(HV)	(HB)
≥ 170	≥ 450	≥ 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

Creep Properties

Heat Treatment	Testing temp. (℃)	Creep rupture strength			Creep strength
		100 hr	1000 hr	10000 hr	1%/10000hr	1%/100000hr
1150℃ Solution treatment	650	228	169	110	109	76
	704	162	110	73	54	39
	760	99	66	45	31	24
	816	64	42	25	22	16
980℃ Annealing	650	214	158	103	79	54
	704	121	73	38	34	23
	760	81	43	23	20	13
	816	56	30	17	8	3

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Heat Treatment

NAS 800H/NAS 800T exhibit an austenite structure similar to austenitic stainless steels, and the heat treatment is similar. Typical heat treatments are as follows:

• Annealing 980-1100℃ Rapid cooling
• Stress relief annealing 780-870℃ Air cooling

When creep rupture strength is needed in a high-temperature environment, the following ASTM B409 heat treatment may be used:

• Solution treatment temperature between at least 1121℃/rapid cooling at least 1149℃

Workability

Whether hot working or cold working, NAS 800H / 800T have 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 800H / 800T as with standard austenitic stainless.

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 800H / 800T have superior corrosion resistance in such oxidizing corrosive environments as nitric acid and nitric acid-sulfuric acid. They perform similarly well in sodium salt and other molten salt environments, and provide stress corrosion crack sensitivity surpassing standard austenitic stainless steels.

Applications

NAS 800H / 800T are widely used in chemical plants, heat treatment furnaces and other high-temperature environments.