Alloy 825
Material
Alloy 825, UNS N08825, W.Nr.2.4858, NS1402
Overview
Alloy 825 is a titanium stabilized full austenitic nickel-iron-chromium alloy with additions of molybdenum, copper, and titanium. The alloy’s chemical composition is designed to provide exceptional resistance to many corrosive environments. The nickel content is sufficient for resistance to chloride-ion stress-corrosion cracking. The nickel, in conjunction with the molybdenum and copper, also gives outstanding resistance to reducing environments such as those containing sulfuric and phosphoric acids. The molybdenum also aids resistance to pitting and crevice corrosion. The alloy’s chromium content confers resistance to a variety of oxidizing substances such as nitric acid, nitrates and oxidizing salt. The titanium addition serves, with an appropriate heat treatment, to stabilize the alloy against sensitization to intergranular corrosion.
Character
- ◎ Good resistance to stress-corrosion cracking
- ◎ Satisfactory resistance to pitting and crevice corrosion
- ◎ Good resistance to oxidising and non-oxidising hot acids
- ◎ Good mechanical properties at both room and elevated temperatures up to approximately 550˚C (1020˚F)
- ◎ Permission for pressure-vessel use at wall temperatures up to 425˚C (800˚F)
Application
The resistance of alloy 825 to general and localized corrosion under diverse conditions gives the alloy broad usefulness. Applications include chemical processing, pollution control, oil and gas recovery, acid production, pickling operations, nuclear fuel reprocessing, and handling of radioactive wastes.
Chemical composition (wt% as per ASTM B163)
| Material | Fe | Ni | Cu | Mo | Mn | C |
|---|---|---|---|---|---|---|
| Alloy 825 | ≥22.0 | 38.0-46.0 | 1.50-3.0 | 2.5-3.5 | ≤1.0 | ≤0.05 |
| Material | Si | S | Cr | Al | Ti | |
| Alloy 825 | ≤0.50 | ≤0.030 | 19.5-23.5 | ≤0.20 | 0.60-1.20 |
Mechanical property
Alloy 825 has good mechanical properties from cryogenic temperatures to moderately high temperatures. Exposure to temperatures above about 1000°F (540°C) can result in microstructural changes (phase formation) that significantly lower ductility and impact strength. For that reason, the alloy is not normally used at temperatures where creep-rupture properties are design factors.
Alloy 825 in annealed condition as per ASTM B163
| Material | Tensile strength ksi (MPa) |
Yield strength at 0.2 offset ksi (MPa) |
Elongation in 2” % min. |
|---|---|---|---|
| Alloy 825 | ≥85 (586) | ≥35 (241) | ≥30 |
Corrosion resistance
The outstanding attribute of Alloy 825 is its high level of corrosion resistance. In both reducing and oxidize environments, the alloy resists general corrosion, pitting, crevice corrosion, intergranular corrosion, and stress-corrosion cracking. Some environments in which Alloy 825 is particularly useful are sulfuric acid, phosphoric acid, sulfur- containing flue gases, sour gas and oil wells, and sea water.
Available Process
Cold worked and bright annealed
Cold worked, bright annealed, polished (MP, EP etc.)
Common Tests
- ◎ Chemical composition
- ◎ Tension
- ◎ Hardness
- ◎ Flaring
- ◎ Flange
- ◎ Flattening
- ◎ Micro structure
- ◎ Hydrostatic
- ◎ NDT
- ◎ Intergranular Corrosion
- ◎ Surface condition
- ◎ Shape and dimension
- ◎ Positive Material Identification
Product forms
Capillary tube
- ◎ OD 0.30 ~ 3.0 mm
- ◎ WT 0.05 ~ 0.5 mm
Precision seamless tube
- ◎ OD 3.0 ~ 89 mm
- ◎ WT 0.10 ~ 10.0 mm
HP / UHP BA+ tube
- ◎ OD 3.0 ~ 76 mm
- ◎ WT 0.10 ~ 10.0 mm
Service
- ◎ Precision cutting
- ◎ Tube surface treatment, like ID surface super mirror polishing, best level could reach Ra0.0015um
- ◎ Tube deep processing, like coiling, bending, end forming, body forming, laser processing, various needles processing, built to drawing and sample, etc.