Extensive stability studies have shown the absence of embrittlement and intermediate metallic phases such as the SIGMA phase, when Inconel 625 alloy is held at temperatures in the 538 °C (1000°F) to 982°C(1800°F) range for a long time.
Alloy 625 may be produced by the method of Vacuum Induction Melting or Argon Oxygen Decarburization (AOD). Further refining can be done by the Self-consuming Electrode Redissolution method.
3.2 Inconel 625 Approximate Grades
China GB |
USA UNS |
Germany SEW VDIUV |
UK BS |
France AFNOR |
NS3306 |
N06625 |
W.Nr.2.4856NiCr22Mo9Nb |
NA21 |
NC 22 DNb |
IV, Particular properties of Inconel625
4.1
Excellent corrosion resistance to various corrosive media in oxidizing and reducing environments.
4.2.
Excellent resistance to pitting corrosion and crevice corrosion, high nickel content to enhance the resistance to chloride stress corrosion cracking.
4.3
Excellent resistance to inorganic acid corrosion, such as nitric acid, phosphoric acid, sulfuric acid, hydrochloric acid and sulfuric acid and hydrochloric acid mixed acid, etc.
4.4
Excellent resistance to corrosion of mixed solutions of various inorganic acids
4.5
It has good corrosion resistance in various concentrations of hydrochloric acid solution when the temperature reaches 40℃.
Simulated pipeline gas desulphurization tests have shown that Inconel 625 has better corrosion resistance than stainless Steel 316 and that Inconel 625 almost with the same corrosion resistance as Hastelloy C-276.
This is illustrated by the following data. Typical corrosion rates are in mils/year (mm/a).Boiling solution of organic acids
|
45% formic acid |
10% oxalic acid |
88% formic acid |
99% acetic acid |
Inconel 625 |
5.0 (0.13) |
6.0 (0.15) |
9.0 (0.23) |
0.4 (0.01) |
SUS 316 |
11 (0.28) |
40 (1.02) |
9 .0 (0.23) |
2.0 (0.05) |
Dilution to reduce acid content - boiling solution
|
1% sulfuric |
5% sulfuric |
10% sulfuric |
1% HCl |
Inconel 625 |
2.2 (0.06) |
8.9 (0.23) |
25.3 (0.64) |
36.3 (0.92) |
SUS 316 |
25.8 (0.65) |
107 (2.72) |
344 (8.73) |
200 (5) |
Hybrid Environments
Environment |
Inconel 625 |
SUS 316 |
20% phosphoric acid |
0.36 (<0.01) |
6.96 (0.18) |
10% sulfanilic acid |
4.80 (0.12) |
63.6 (1.61) |
10% sodium bisulfate |
3.96 (0.10) |
41.6 (1.06) |
Resistance to chloride stress corrosion fission test
Test |
Inconel 625 |
SUS 316 |
42% Magnesium chloride |
No fission |
fission |
1000 hours |
<24 hours |
26% Sodium chloride |
Non-fissile |
fissile |
1000 hrs |
600 hrs |
4.6
Good workability and weldability, no susceptibility to post-weld cracking
4.7
High strength below 650°C, good molding, easy to weld; The maximum operating temperature is 1175°C in the atmosphere.
4.8
Has pressure vessel manufacturing certification for wall temperature of -196 ~ 450 ℃.
4.9
Certified by the American Association of Corrosion Engineers NACE standards (MR-01-75) in line with the highest standard class VII for use in acid gas environments.
V, Other Properties
5.1 Physical Properties:
Density g/cm3 |
8.44 |
Melting point ℃ |
1290-1350 |
Thermal conductivity λ/(W/m•°C) |
12.1(100°C) |
Specific heat capacity J/kg•°C |
430 |
Modulus of elasticity GPa |
205 |
Shear modulus GPa |
79 |
Resistivity μΩ•m |
1.28 |
Poisson's ratio |
308 |
Coefficient of linear expansion a/10-6℃-1 |
12.3 (20~100℃) |
5.2 Mechanical properties of inconel625:
Minimum value of mechanical properties tested at 20℃.
Heat treatment Solid solution treatment
Tensile strength σb/MPa |
Yield strength σp0.2/MPa |
Elongation σ5 /% |
Brinell hardness HBS |
830 |
410 |
30 |
≤290 |
VI, Process performance of inconel625
6.1 Hot processing for Inconel625
6.1.1
The cooling method is water quenching or other rapid cooling methods when the hot working temperature is from 1150°C to 900°C.
6.1.2
To get the best performance and corrosion resistance, annealing treatment should be carried out after hot working.
6.1.3
When heated, the Inconel625 material can be fed directly into the furnace that has been warmed up to the maximum working temperature, and quickly withdraw the material from the furnace after holding for a sufficient time (60 minutes per 100 mm thickness). The hot working shall be down in the specified temperature range of the high-temperature section. If the material temperature drops below the hot working temperature, it shall be reheated.
6.2 Cold working of Inconel625
6.2.1
The Inconel 625 materials shall be in the annealed state with a greater work-hardening rate than austenitic chromium-nickel stainless steels.
6.2.2
Intermediate annealing is required for cold working.
6.2.3
When the machining quantity is greater than 15%, annealing is to be carried out after hot working.
6.3 Machining
6.3.1
Inconel625 has good cold and hot forming properties, forging heating temperature is 1120 ℃.
6.3.2
The average grain size of Inconel625 is closely related to the degree of deformation of the forgings and the final forging temperature.
Inconel625 welding property is good.