Nippon Yakin Kogyo NAS825 Corrosion Resistant Alloys

Manufacturer: Nippon Yakin Kogyo Co., Ltd
Model : NAS825

NAS825 (UNS N08825)
High Corrosion Resistant Nickel Alloy

NAS825 (NCF825, UNS N08825) is a high-Ni nickel alloy with high corrosion resistance, and possesses extremely high corrosion resistance against oxidizing and non-oxidizing acids. Nippon Yakin supplies this product in plate, sheet and strip form.

Chemical Composition	40Ni 23Cr 3Mo 2Cu 0.71Ti
Product shape	Coil	Sheet	Plate
Workability	Cold and hot workability approximately equal to Type 304, 316, and other standard austenitic stainless steels.
Weldability	Shielded metal arc welding, TIG welding, MIG welding are possible. Use Alloy 625, CNiCrMo-3 welding consumables.
Machinability	Machinability equivalent to standard austenitic stainless steels. Use high-speed steel tool or super-hard tool, slow feed speed, and large cut depth are advised.
Heat Treatment	Solution annealing at 930–1030°C, followed by quenching in water or rapidly cooling.
Pickling	Nitric acid and hydrofluoric acid are used. High corrosion resistance of NAS625 makes scale removal difficult. Alkaline solution immersion before pickling recommended.
Applications	Chemical plants, Oil and gas extraction, Sheathed heater, Umbilical cable.

Steel Grade/Standard

Nippon Yakin Grade	JIS G 4902	ASTM B424	DIN 17750
NAS825	NCF825	UNS N08825	2.4858

Chemical Composition

	C	Si	Mn	P	S	Ni	Cr	Fe	Mo	Cu	Al	Ti
Specification (NCF825)	≤0.05	≤0.50	≤1.00	≤0.030	≤0.015	38.00-46.00	19.50-23.50	Bal.	2.50-3.50	1.50-3.00	≤0.20	0.60-1.20
Specification (UNS N08825)	≤0.05	≤0.5	≤1.0	—	≤0.03	38.0-46.0	19.5-23.5	≥22.0	2.5-3.5	1.5-3.0	≤0.20	0.6-1.2

Physical Properties

Density [g/cm³]	8.14
Specific heat [J/kg•K] (20°C)	444
Electrical resistivity [μΩ•cm]	112
Thermal conductivity [W/m•K]	10.9
Average coefficient of thermal expansion [10⁻⁶/°C]	20–100°C 13.4
	20–200°C 14.1
	20–500°C 15.1
	20–900°C 16.9
Young’s modulus [MPa]	19.7 × 10⁴
Magnetism	None
Melting range [°C]	1370–1400

Mechanical Properties

Mechanical Properties at Room Temperature

	0.2% proof stress (MPa)	Tensile strength (MPa)	Elongation (%)	Hardness (HRB)
Specification (NCF825)	≥235	≥580	≥30	≤207
Specification (UNS N08825)	≥241	≥586	≥30	≤207
Cold-rolled sheet (1.0mm)	263	612	47	144
Hot-rolled plate (8.0mm)	250	612	54	144
Hot-rolled plate (33.6mm)	235	588	48	137

High Temperature Strength

Corrosion Resistance

Because NAS825 has high contents of chromium, molybdenum, and copper, it provides excellent general (overall) corrosion resistance against oxidizing and non-oxidizing acids. Corrosion resistance against sulfuric acid is particularly good. Due to its high contents of chromium, molybdenum, and nickel, pitting corrosion resistance, crevice corrosion resistance, and stress corrosion cracking (SCC) resistance under chloride environments are also excellent in comparison with Type 316L. Because the carbon content of NAS825 is held to an extremely low level, sensitization during welding is minimal, and this is also an alloy with low grain boundary corrosion sensitivity.

Pitting Corrosion Resistance

Alloy	ASTM G48 Method A	ASTM G48 Method C Critical pitting corrosion temperature CPT (°C)
SUS316L	—	15
NAS329J3L	○	50
NAS254N	○	80
NAS825	○	60

Test conditions: ASTM G48 Method A (○: No pitting corrosion, X: Pitting corrosion)
– Test solution: 6% FeCl₃
– Test temperature: 22°C, 50°C (Recommended temperature in this test)
– Test time: 72h

Crevice Corrosion Resistance

Alloy	ASTM G48 Method D
SUS316L	<10
NAS329J3L	25
NAS254N	45
NAS825	10

Test conditions: ASTM G48 Method D
– Test solution: 6% FeCl₃ + 1% HCl
– Test time: 72h

Stress Corrosion Cracking Resistance

Alloy	MgCl₂ concentration (boiling point °C in brackets)	42% (153°C)	35% (146°C)	25% (119°C)
SUS316L	x	x	x	x
NAS329J3L	○	○	x	x
NAS254N	○	○	○	○
NAS825	○	○	○	○

Test conditions:
– Immersion in boiling MgCl₂ solution.
– Test time: 300h.
○: No stress corrosion cracking, x: Stress corrosion cracking.

Acid Resistance

Corrosion Rate in Sulfuric Acid at 80°C (mm/y)

Alloy	5%	10%	20%	40%	60%	80%
SUS316L	1.07	4.69	7.11	764.9	704.5	33.74
NAS329J3L	0.01	0.17	0.46	385.9	1456	108.4
NAS254N	0.02	0.05	0.08	2.16	7.73	2.03
NAS825	0.03	0.10	0.22	0.73	0.23	0.73

Corrosion Rate in Hydrochloric Acid at 80°C (mm/y)

Alloy	0.1%	1%	3%	5%
SUS316L	0.06	0.73	14.88	31.44
NAS329J3L	0.02	0.27	3.76	11.86
NAS254N	0.01	0.01	0.04	0.11
NAS825	0.01	0.22	2.26	3.14

Test time: 24h

Reference

Alloy	JIS	UNS No.	Chemical Composition
SUS316L	SUS316L	S31603	17Cr-12Ni-2Mo
NAS329J3L	SUS329J3L	S32205	22Cr-5.3Ni-3.0Mo-0.16N
NAS254N	SUS329J4L	S32506	25Cr-6.8Ni-3.5Mo-0.17N
NAS825	NCF825	N08825	40Ni-23Cr-3Mo-2Cu-0.7Ti

Workability

Cold and hot workability are approximately equal to those of standard austenitic stainless steels.

Weldability

Possible welding methods include shielded metal arc welding, TIG welding, and MIG welding, in the same manner as with standard austenitic stainless steels. As welding consumables, Alloy 625, DNiCrMo-3 should be used.

Machinability

NAS825 has machinability approximately equivalent to standard austenitic stainless steels. In machining, use of a high-speed steel tool or superhard tool and a slow feed speed and large cut depth are advised.

Heat Treatment

Solution annealing of NAS825 is normally performed at the temperature range from 930 to 1030°C followed by being quenched in water or rapidly cooled by other means.

Pickling

A mixture of nitric acid and hydrofluoric acid is used in pickling. However, due to the high corrosion resistance of NAS825, scale is somewhat difficult to remove in comparison with Type 304. Therefore, the material should be immersed in an alkaline solution before pickling, or if possible, shot blasting is extremely effective.