Corrosion Resistant Alloys
NAS 825 (UNS N08825), comparable to Incoloy® 825 Alloy
A powerful corrosion-resistant alloy with a high nickel content, NAS 825 (NCF 825, UNS N08825), comparable to Incoloy® 825 Alloy, provides strong resistance against oxidizing and non-oxidizing acids. Nippon Yakin supplies this product in plate, sheet and strip forms.
Coil
Sheet
Plate
Chemical Composition
NCF 825
| C | Si | Mn | P | S | Ni | Cr | Fe | Mo | Cu | Al | Ti | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | 38.00 | 19.50 | Balance | 2.50 | 1.50 | ― | 0.60 |
| Max | 0.05 | 0.50 | 1.00 | 0.030 | 0.015 | 46.00 | 23.50 | Balance | 3.50 | 3.00 | 0.2 | 1.20 |
UNS N08825
| C | Si | Mn | P | S | Ni | Cr | Fe | Mo | Cu | Al | Ti | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | ― | ― | ― | ― | ― | 38.0 | 19.5 | 22.0 | 2.5 | 1.5 | ― | 0.6 |
| Max | 0.05 | 0.5 | 1.0 | ― | 0.03 | 46.0 | 23.5 | ― | 3.5 | 3.0 | 0.2 | 1.2 |
Physical Properties
| Specific heat (J/kg･K) | 20℃ | 444 |
| Specific resistivity (μΩ･cm) | 112 | |
| Thermal conductivity (W/m･K) | 10.9 | |
| Coefficient of thermal expansion (10-6/℃) | 20–100℃ | 13.4 |
| 20–200℃ | 14.1 | |
| 20–500℃ | 15.1 | |
| 20–900℃ | 16.9 | |
| Young's modulus (MPa) | 19.4 x 104 | |
| Ferromagnetism | None | |
| Melting point (℃) | 1370-1400 | |
Mechanical Properties
Mechanical Properties at Room Temperature
NCF 825
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness (HB) |
|---|---|---|---|
| ≥ 235 | ≥ 580 | ≥ 30 | ≥ 207 |
ASTM B424
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness (HB) |
|---|---|---|---|
| ≥ 241 | ≥ 586 | ≥ 30 | ― |
Examples
| 0.2% proof stress (N/mm2) |
Tensile strength (N/mm2) |
Elongation (%) |
Hardness (HB) |
|
|---|---|---|---|---|
| Cold-rolled sheet, 1.0-mm thick |
262 | 612 | 46.6 | ― |
| Hot-rolled plate, 8.0-mm thick |
253 | 615 | 54 | 144 |
| Hot-rolled plate, 33.5-mm thick |
255 | 616 | 48 | 137 |
High-Temperature Strength
Corrosion Resistance
Because of its high chromium, molybdenum and copper content, NAS 825 provides superior general corrosion resistance against oxidizing and non-oxidizing acids. In particular, NAS 825 is particularly resistant to sulfuric acid. The high chromium, molybdenum and nickel content also provides more powerful resistance to pitting corrosion, crevice corrosion and stress corrosion than SUS 316L in chloride environments. We have held the carbon content to as low as possible to minimize sensitization during welding as well as lower the susceptibility to grain boundary corrosion.
Corrosion resistance to sulfuric acid
Pitting and Crevice Corrosion Resistance
Stress Corrosion Cracking Resistance
Stress corrosion cracking test in boiling magnesium chloride solution – U-bending test, immersion for 300 hours
| SUS 316L | NAS 329J3L | NAS 825 | NAS 254N | |
|---|---|---|---|---|
| Boiling 42% MgCl2* | × | × | × | × |
| Boiling 35% MgCl2* | × | × | ○ | ○ |
| Boiling 25% MgCl2* | × | ○ | ○ | ○ |
| Boiling 20% MgCl2* | ○ | ○ | ○ | ○ |
○: No stress corrosion cracks
×: Stress corrosion cracks
* JIS G0576 – Stainless steel stress corrosion crack test method
Intergranular Corrosion Resistance
Grain boundary corrosion test (JIS G0572) – immersion in a boiling test solution of 50% H2SO4-Fe2(SO4)3 for 120 hours, sensitization heat treatment: 650° C for 2 hours
Workability
NAS 825 can be cold- and hot-worked nearly the same as standard austenitic stainless steels.
Weldability
Such welding techniques as TIG, MIG and shield metal arc welding can be used for NAS 825 as with standard austenitic stainless steels. We recommend Inconel® 625 and DNiCrMo-3 for consumables.
Machinability
NAS 825 is very similar to standard austenitic stainless steels when it comes to machinability. An effective approach to cutting is using a high-speed or ultra-hard cutting tool and combining a slower feed rate with a greater cutting depth.
Heat Treatment
Heat treatment is as with a stable austenitic stainless steel such as SUS 321. Use a solution treatment slightly cooler than SUS 304 and water cool between 920 and 1030℃.
- Solution treatment 1125–1175℃ Water cooling
Pickling
A mixture of nitric and hydrofluoric acids is used in pickling. To the extent that NAS 825 is more resistant to corrosion than SUS 304, descaling is more difficult. Alkaline immersion for a short time before acid pickling and shot blasting if possible are effective at descaling.
* Incoloy and Inconel are registered trademarks of Special Metals Corporation.
