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Specification
Sheet: Alloy 625 (UNS N06625)
Alloy 625 Nickel-Base Superalloy |
Applications
| Standards | Chemical Analysis
Corrosion and Oxidation Resistance
| Formability | Mechanical
Properties
Welding | Heat Treatment
| Physical Properties | Impact
Resistance
|
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| Alloy 625
(UNS N06625) is an austenitic nickel base superalloy possessing
excellent resistance to oxidation and corrosion over a
broad range of corrosive conditions, including jet engine
environments and in many other aerospace and chemical
process applications. The alloy has outstanding strength
and toughness at temperatures ranging from cryogenic temperature
to 2000°F (1093°C). Alloy 625 also has exceptional
fatigue resistance.
Alloy 625 derives its strength from the
solid solution strengthening effects of molybdenum and
columbium on the nickel-chromium matrix. These elements
also contribute to the alloy’s outstanding corrosion
resistance. Although the alloy was developed for high
temperature strength, its highly alloyed composition provides
a high level of general corrosion resistance to a wide
range of oxidizing and nonoxidizing environments. The
levels of chromium and molybdenum provide excellent resistance
to chloride ion pitting and the high level of nickel provides
resistance to chloride stress corrosion cracking.
The material possesses a high degree of
formability and shows better weldability than many highly
alloyed nickel-base alloys. The alloy is resistant to
intergranular corrosion even in the welded condition.
Alloy 625 can be produced by vacuum induction
melting or AOD refining. Consumable electrode remelting
procedures may be used to further refine the material.
|
| Applications
- Seawater applications
- Aerospace components
- Chemical processing equipment
- Nuclear water reaction components
|
| Standards |
| AMS........... |
5599 |
| ASTM.......... |
B 443 |
| ASME.......... |
SB 443 |
|
Chemical
Analysis
Typical
Analysis (Weight %)
| C |
Mn |
P |
S |
Si |
Cr |
Ni |
Mo |
Columbium
+ Ta |
Ti |
Al |
Fe |
| 0.05 |
0.030 |
0.010 |
0.003 |
0.25 |
22.0 |
Balance |
9.0 |
3.5 |
0.3 |
0.3 |
4.0 |
|
| Corrosion
and Oxidation Resistance
The high level of
chromium and molybdenum in Alloy 625 provides a high level
of pitting and crevice corrosion resistance to chloride
contaminated media, such as seawater, neutral salts and
brines.
Typical Data in Chloride
Solutions
| Crevice Test in 10 Percent
Ferric Chloride |
Type 316 |
Alloy 625 |
Onset Temperature °F (°C)
for Attack in ASTM Procedure G-48 |
<32 (<0) |
104-113 (40-45) |
Panel Exposures in Seawater
| Panel Location Onset Temperature |
Type 316 |
Alloy 625 |
| Flowing Seawater |
Crevice Attack
1 Month |
No Attack
18 Months |
| Tidal Zone |
Crevice Attack
1 Month |
No Attack
18 Months |
| Partial Mud Burial |
Crevice Attack
1 Month |
No Attack
18 Months |
The alloy is resistant to a variety of
corrosive media from highly oxidizing to moderately reducing.
Tests in geothermal brines indicate Alloy
625 is highly resistant to hot geothermal fluids comparable
to Titanium Grade 2.
Tests in simulated flue gas desulfurization
environments show Alloy 625 highly resistant to the environment
in comparison to alloys such as Type 316 and comparable
to Alloy 276.
The following data are illustrative. Typical
corrosion rates are in mils/year (mm/a).
Boiling Organic Acid Solutions
| Alloy |
45% Formic |
10% Oxalic |
88% Formic |
99% Acetic |
| Alloy 625 |
5.0 (0.13) |
6.0 (0.15) |
9.0 (0.23) |
0.4 (0.01) |
| Type 316 |
11 (0.28) |
40 (1.02) |
9.0 (0.23) |
2.0 (0.05) |
Dilute Reducing Acids —
Boiling Solutions*
| Alloy |
1% Sulfuric |
5% Sulfuric |
10% Sulfuric |
1% Hydrochloric |
| Alloy 625 |
2.2 (0.06) |
8.9 (0.23) |
25.3 (0.64) |
36.3 (0.92) |
| Type 316 |
25.8 (0.65) |
107 (2.72) |
344 (8.73) |
200 (5) |
* Sulfuric acid test samples activated
before tests and hydrochloric acid test samples tested
without activation.
Miscellaneous Environments
| Environment |
Alloy 625 |
Type 316 |
| 20% Phosphoric Acid |
.36 (<0.01) |
6.96 (0.18) |
| 10% Sulfamic Acid |
4.80 (0.12) |
63.6 (1.61) |
| 10% Sodium Bisulfate |
3.96 (0.10) |
41.6 (1.06) |
Chloride
Stress Corrosion Cracking Resistance
| Test |
Alloy 625 |
Type 316 |
Alloy 20 |
| 42% Magnesium Chloride |
No Cracks
1000 Hours |
Cracks
<24 Hours |
Cracks
<100 Hours |
| 26% Sodium Chloride |
No Cracks
1000 Hours |
Cracks
600 Cracks |
No Cracks
1000 Cracks |
Oxidation
Resistance
 Alloy
625 has excellent oxidation and scaling resistance at
temperatures up to 2000°F (1093°C). It is superior
to many other high temperature alloys under cyclic heating
and cooling conditions. The following graph compares the
weight loss of several stainless steel alloys to Alloy
625 under cyclic oxidation at 1800°F (982°C).
|
| Formability
Alloy 625 is capable of
being formed like the standard austenitic stainless steels.
The material is considerably stronger than conventional
austenitic stainless steels and consequently requires
higher loads to cause the material to deform. During cold
working, the material work hardens more rapidly than austenitic
stainless steels. The combination of high initial strength
and work hardening rate may necessitate need for intermediate
anneals if the cold deformation is extensive.
Effect of Cold Reduction
on Properties of Plate Annealed at 2150°F (1177°C)
Cold
Reduction |
Hardness
Rockwell C |
Yield Strength
(02.% Offset) |
Tensile Strength |
Elongation |
Reduction of Area |
| % |
|
psi |
(Mpa) |
psi |
(Mpa) |
% |
% |
| 0 |
88Rb |
49,500 |
341 |
115,500 |
796 |
67.0 |
60.4 |
| 5 |
94Rb |
77,500 |
534 |
121,000 |
834 |
58.0 |
58.1 |
| 10 |
25 |
102,500 |
707 |
130,000 |
896 |
47.5 |
54.6 |
| 15 |
32 |
112,500 |
776 |
137,000 |
945 |
39.0 |
51.9 |
| 20 |
34 |
125,000 |
862 |
143,000 |
986 |
31.5 |
50.0 |
| 30 |
36 |
152,000 |
1048 |
165,000 |
1137 |
17.0 |
49.3 |
| 40 |
39 |
167,000 |
1151 |
179,500 |
1238 |
12.5 |
41.9 |
| 50 |
40 |
177,000 |
1220 |
189,500 |
1307 |
8.5 |
38.0 |
| 60 |
44 |
180,500 |
1245 |
205,000 |
1413 |
6.5 |
32.7 |
| 70 |
45 |
201,000 |
1386 |
219,000 |
1510 |
5.0 |
25.4 |
|
| Mechanical
Properties
Typical
Short Time Tensile Properties as a Function of Temperature
Typical room temperature
tensile properties of material annealed at
1920°F (1065°C) follow.
| Yield Strength (0.2%
Offset) |
Ultimate Tensile Strength |
Elongation (% in 2") |
| 63,000 psi (430 MPa) |
136,000 psi (940 MPa) |
51.5 |
The typical room temperature tensile properties
of material solution annealed at 2150°F (1177°C)
follow.
| Yield Strength (0.2%
Offset) |
Ultimate Tensile Strength |
Elongation (% in 2") |
| 49,500 psi (340 MPa) |
115,500 psi (800 MPa) |
67 |
The short time elevated temperature tensile
properties of Alloy 625 annealed at 1950°F (1066°C)
are shown in the following graph.
|
| Welding
Alloy 625 can be readily welded by conventional processes
used for austenitic stainless steel, including fusion
and resistance methods. The material should be in the
mill annealed condition and thoroughly descaled and cleaned
before welding. Preheating is not required and post-weld
treatment is not needed to maintain or restore corrosion
resistance.
|
Heat
Treatment
Alloy 625 is furnished
with one heat treatment for optimum properties up to
1200°F (649°C) and another for optimum properties
above 1200°F (649°C). The standard anneal at a
minimum of 1600°F (871°C) is used for service
temperatures up to 1200°F (649°C). When optimum
high temperature creep and rupture properties are required,
as for service above 1200°F (649°C), a solution
anneal at
2000°F (1093°C) minimum is used. In the solution
annealed condition, a subsequent stabilization anneal
at 1800°F (982°C) minimum is sometimes specified
to further increase resistance to sensitization.
|
| Physical
Properties
|
Density :
0.305 Ib/in3
8.44 g/cm3
Specific Gravity
:
8.44
Melting Range
2350°-2460°F
1280°-1350°C
Magnetic Permeability
75°F, 200 oersted 1.0006
Specific Heat
:
0.098 Btu/lb.-°F
410 Joules/kg-°K
|
Electrical
Resistivity:
0.098 Btu/lb.-°F
410 Joules/kg-°K
| Temperature |
Electrical
Resistivity
microhm-cm |
| °F |
(°C) |
| 70 |
21 |
128.9 |
| 100 |
38 |
129.6 |
| 200 |
93 |
131.9 |
| 400 |
204 |
133.9 |
| 600 |
316 |
134.9 |
| 800 |
427 |
135.9 |
| 1000 |
538 |
137.9 |
| 1200 |
649 |
137.9 |
| 1400 |
760 |
136.9 |
| 1600 |
871 |
135.9 |
| 1800 |
982 |
134.9 |
| 2000 |
1093 |
133.9 |
|
Thermal Properties
| Temperature |
Linear Coefficient
of Thermal
Expansion (a) (Units of 10-6) |
Thermal Conductivity
(b) (c) |
| °F |
°C |
/ °F |
/ °C |
Btu-ft / ft2 h-°F |
W/m-°K |
| -250 |
-157 |
– |
– |
4.2 |
7.3 |
| -200 |
-129 |
– |
– |
4.3 |
7.4 |
| -100 |
-73 |
– |
– |
4.8 |
8.3 |
| 0 |
-18 |
– |
– |
5.3 |
9.2 |
| 70 |
21 |
– |
– |
5.7 |
9.9 |
| 100 |
38 |
– |
– |
5.8 |
10.0 |
| 200 |
93 |
7.1 |
12.8 |
6.3 |
10.7 |
| 400 |
204 |
7.3 |
13.1 |
7.3 |
12.6 |
| 600 |
316 |
7.4 |
13.3 |
8.2 |
14.2 |
| 800 |
427 |
7.6 |
13.7 |
9.1 |
15.7 |
| 1000 |
538 |
7.8 |
14.0 |
10.1 |
17.5 |
| 1200 |
649 |
8.2 |
14.8 |
11.0 |
19.0 |
| 1400 |
760 |
8.5 |
15.3 |
12.0 |
20.8 |
| 1600 |
871 |
8.8 |
15.8 |
13.2 |
22.8 |
| 1700 |
927 |
9.0 |
16.2 |
– |
– |
| 1800 |
982 |
– |
– |
14.6 |
25.3 |
(a) Average coefficient from 70°F
(21°C) to temperature shown.
(b) Measurements made at Battelle Memorial Institute.
(c) Material annealed 2100°F (1149°C).
Modulus Data
| Temperature |
Modulus of Rigidity
(G) |
Elastic Modulus
(E) |
Poisson's Ratio (a) |
| °F |
°C |
Units of 106 psi |
Units Gpa |
Units of 106 psi |
Units Gpa |
(µ) |
| 70 |
21 |
11.4 |
79 |
29.8 |
205 |
0.308 |
| 200 |
93 |
11.2 |
77 |
29.2 |
200 |
0.310 |
| 400 |
204 |
10.8 |
75 |
28.4 |
195 |
0.312 |
| 600 |
316 |
10.5 |
72 |
27.5 |
190 |
0.313 |
| 800 |
427 |
10.1 |
70 |
26.6 |
185 |
0.312 |
| 1000 |
538 |
9.7 |
67 |
25.6 |
175 |
0.321 |
| 1200 |
649 |
9.2 |
63 |
24.4 |
170 |
0.328 |
| 1400 |
760 |
8.7 |
60 |
23.1 |
160 |
0.329 |
| 1600 |
871 |
8.2 |
57 |
– |
– |
– |
(a) Poisson’s ratio (m) computed
from the relation: µ = E-2G/2G
|
Impact
Resistance
Alloy 625
maintains high impact resistance at low temperatures as
shown below.
Typical Alloy 625 Impact
Properties
| Test
Temperature |
Orientation |
Impact
Energy (a) |
| °F |
°C |
Ft-lbs |
Joules |
| 85 |
30 |
Longitudinal |
49 |
66 |
| 85 |
30 |
Transverse |
49 |
66 |
| -110 |
- 79 |
Longitudinal |
44 |
60 |
| -110 |
- 79 |
Transverse |
41.5 |
56 |
| -320 |
-196 |
Longitudinal |
35 |
47 |
| -320 |
-196 |
Transverse |
35 |
47 |
(a) Charpy Keyhole Specimens (Mean Value
of 3 Tests)
Impact properties may be expected to decrease
with extended service in the 1200° to 1600°F
(649° to 871°C) range.
|
| NOTE
This technical data and information represents our best
knowledge at the time of printing. However, it may be
subject to some slight variations due to our ongoing research
program on corrosion resistant grades. We, therefore,
suggest that information be verified at time of inquiry
or order. Furthermore, in service, real conditions are
specific for each application. The data presented here
is only for the purpose of description and may only be
considered as guarantees when our Company has given written
formal approval.
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