INCOLOY® alloy 825 (UNS N08825/W.Nr. 2.4858) is a
nickel-iron-chromium alloy with additions of
molybdenum, copper, and titanium. The alloy’s
chemical composition, given in Table 1, 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.
The resistance of INCOLOY alloy 825 to general
and localized corrosion under perse 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.
Applications for alloy 825 are similar to those for
INCOLOY alloy 020.
Table 1 - Limiting Chemical Composition, % of INCOLOY alloy 825
Nickel ..........................................................................38.0-46.0
Iron...............................................................................22.0 min.
Chromium....................................................................19.5-23.5
Molybdenum ...................................................................2.5-3.5
Copper ............................................................................1.5-3.0
Titanium...........................................................................0.6-1.2
Carbon........................................................................0.05 max.
Manganese ...................................................................1.0 max.
Sulfur ..........................................................................0.03 max.
Silicon ...........................................................................0.5 max.
Aluminum......................................................................0.2 max.
Physical Constants and Thermal
Properties
Some physical constants for INCOLOY alloy 825 are
listed in Table 2. Values for thermal expansion, thermal
conductivity, and electrical resistivity at various
temperatures are in Table 3. Modulus of elasticity and
Poisson’s ratio over a range of temperatures are given in
Table 4. Modulus values, which were determined
dynamically, were used to compute Poisson’s ratio.
Table 2 - Physical Constants
Density, lb/in3.....................................................................0.294
Mg/m3 ....................................................................8.14
Melting Range, °F .....................................................2500-2550
°C .....................................................1370-1400
Specific Heat, Btu/lb•°F ....................................................0.105
J/kg•°C .........................................................440
Curie Temperature, °F.......................................................<-320
°C ......................................................<-196
Permeability at 200 oersted (15.9 kA/m)...........................1.005
Table 3 - Thermal Properties
Temperature Electrical
Resistivity
Thermal
Conductivity
Coefficient of
Expansiona
°F 10-6in/in•°F Btu-in/ft2•h•°F ohm•circ mil/ft
-250 - 55 -
-200 - 59 -
-100 - 66 -
0 - 72.6 -
78 - 76.8 678
100 - 78.4 680
200 7.8 85.0 687
400 8.3 97.5 710
600 8.5 109.6 728
800 8.7 119.7 751
1000 8.8 130.9 761
1200 9.1 141.8 762
1400 9.5 154.9 765
1600 9.7 171.8 775
1800 - 192.0 782
2000 - - 793
°C µm/m•°C W/m•°C µΩ•m
-150 - 7.9 -
-100 - 8.9 -
0 - 10.7 -
25 - 11.1 1.13
100 14.1 12.3 1.14
200 14.8 13.8 1.18
300 15.3 15.4 1.21
400 15.6 16.9 1.24
500 15.8 18.2 1.26
600 16.0 19.6 1.27
700 16.7 21.2 1.27
800 17.3 23.1 1.28
900 - 25.5 1.29
1000 - - 1.30
aMean coefficient of linear expansion between 80°F (27°C) and
temperature shown.
The data contained in this publication is for informational purposes only and
may be revised at any time without prior notice. The data is believed to be
accurate and reliable, but Special Metals makes no representation or warranty of
any kind (express or implied) and assumes no liability with respect to the
accuracy or completeness of the information contained herein. Although the
data is believed to be representative of the product, the actual characteristics or
performance of the product may vary from what is shown in this publication.
Nothing contained in this publication should be construed as guaranteeing the
product for a particular use or application.
Publication Number SMC-030
Copyright © Special Metals Corporation, 2003 (Oct 03)
INCOLOY, INCONEL, INCO-WELD and 686CPT are
trademarks of the Special Metals Corporation group of
companies.
INCOLOY ® alloy 825
2
Temperature Poisson’s
Ratio
Shear
Modulus
Young’s
Modulus
°C GPa GPa
Temperature Poisson’s
Ratio
Shear
Modulus
Young’s
Modulus
°F 103 ksi 103 ksi
73 28.14 10.51 0.34
100 28 10.46 0.34
200 27.46 10.28 0.34
300 26.96 10.08 0.34
400 26.45 9.87 0.34
500 25.88 9.68 0.34
600 25.38 9.48 0.34
700 24.86 9.26 0.34
800 24.37 9.04 0.35
900 23.93 8.82 0.36
1000 23.43 8.6 0.36
1100 22.91 8.37 0.37
1200 22.4 8.13 0.38
1300 21.93 7.89 0.39
1400 21.42 7.64 0.40
1500 20.76 7.38 0.41
1600 19.73 7.12 0.39
1700 18.57 6.8 0.37
1800 17.32 6.48 0.34
23 194.1 72.5 0.34
100 189.0 70.8 0.34
200 182.8 68.2 0.34
300 176.1 65.8 0.34
400 169.5 63.1 0.34
500 164.1 60.3 0.36
600 157.5 57.5 0.37
700 151.5 54.6 0.39
800 145.3 51.4 0.41
900 132.3 48.0 0.38
1000 116.6 43.5 0.34
Mechanical Properties
INCOLOY 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.
Tensile properties at room temperature are listed in Table 5. As indicated, the alloy can be strengthened substantially by
cold work.
High-temperature tensile properties are shown in Figure 1. The tests were conducted on cold-drawn rod of 0.75-in. (19-
mm) diameter annealed at 1725°F (940°C)/1 hr.
Compressive yield strength of the alloy is similar to tensile yield strength. Tests on annealed rod of 1.0-in. (25-mm)
diameter produced a compressive yield strength (0.2% offset) of 61,400 psi (423 MPa) compared with a tensile yield strength
of 57,500 psi (396 MPa). Ultimate tensile strength of the material was 104,500 psi (720 MPa).
INCOLOY alloy 825 has good impact strength at room temperature and retains its strength at cryogenic temperatures.
Table 6 gives the results of Charpy keyhole tests on plate.
Table 5 - Typical Room-Temperature Tensile Properties
Tubing, Annealed 112 772 64 441 36
Tubing, Cold Drawn 145 1000 129 889 15
Bar, Annealed 100 690 47 324 45
Plate, Annealed 96 662 49 338 45
Sheet, Annealed 110 758 61 421 39
Form and
Condition
Elongation,
%
ksi MPa ksi MPa
Tensile Strength Yield Strength
(0.2% Offset)
Figure 1. High-temperature tensile properties of annealed bar.
Indicates the typical usage range.
0
0 100 200 300 400 500 600 700 800 900
120
100
80
60
40
20
0
700
600
500
400
300
200
100
0
200 400 600 800 1000 1200 1400 1600 1800 2000
1000
Stress, ksi Elongation, %
Temperature, °F
Temperature, °C
Stress, MPa
Table 4 - Modulus of Elasticity (Hot Rolled and Annealed Bar)
Tensile Strength
Elongation
Yield Strength
(0.2% Offset)
Orientation
°F °C ft-lb J
Temperature Impact Strengtha
Table 6 - Charpy Keyhole Impact Strength of Plate
Room Room Longitudinal 79.0 107
Transverse 83.0 113
-110 -43 Longitudinal 78.0 106
Transverse 78.5 106
-320 -196 Longitudinal 67.0 91
Transverse 71.5 97
-423 -253 Longitudinal 68.0 92
Transverse 68.0 92
a
Average of three tests.
INCOLOY ® alloy 825
3
Corrosion Resistance
The outstanding attribute of INCOLOY 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 INCOLOY alloy 825 is particularly useful are sulfuric acid, phosphoric acid, sulfurcontaining flue gases, sour gas and oil wells, and sea water.
For details on the corrosion resistance of alloy 825, refer to Special Metals publication “Restistance to Aqueous
Corrosion”, on the website, www.specialmetals.com.
All standard machining operations are readily performed on
INCOLOY alloy 825. The alloy normally has optimum
machining characteristics in the annealed temper. Tooling
and procedures described for Group C alloys should be used;
for more information refer to Special Metals publication
“Machining”, on the website, www.specialmetals.com.
Hot and Cold Forming
The hot-working range for INCOLOY alloy 825 is 1600 to
2150°F (870 to 1180°C). For optimum corrosion resistance,
final hot working should be done at temperatures between
1600 and 1800°F (870 and 980°C).
Cooling after hot working should be air cool or faster.
Heavy sections may become sensitized during cooling from
the hot-working temperature, and therefore be subject to
intergranular corrosion in certain media. A stabilizing anneal
(see above) restores resistance to corrosion. If material is to
be welded or subjected to further thermal treatment and
subsequently exposed to an environment that may cause
intergranular corrosion, the stabilizing anneal should be
performed regardless of cooling rate from the hot-working
temperature.
Cold-forming properties and practices are essentially
the same for INCOLOY alloy 825 as for INCONEL alloy
600. Although work-hardening rate is somewhat less than
for the common grades of austenitic stainless steels, it is still
relatively high. Forming equipment should be well powered
and strongly built to compensate for the increase in yield
strength with plastic deformation.
Additional information on hot and cold forming can be
obtained by visiting the website www.specialmetals.com.
Joining
INCOLOY alloy 825 has good weldability by all
conventional processes. For most applications, INCONEL®
Welding Electrode 112 for shielded metal-arc welding and
INCONEL Filler Metal 625 for gas-shielded processes are
used. For applications that require highest resistance to
corrosion, INCO-WELD® Welding Electrode 686CPT® and
INCO-WELD Filler Metal 686CPT are used. Information on
surface preparation, joint design, and welding technique can
be obtained in the Special Metals publication “Joining”, on
the website, www.specialmetals.com.
Fabrication
INCOLOY alloy 825 products are heat treated during manufacturing at the mill to develop the optimum combination of
corrosion resistance, mechanical properties, and formability. To maintain these properties during fabrication, subsequent
anneals should be performed between 1700 to 1800°F (930 to 980°C) followed by rapid air cooling or water quenching.
General procedures for heating, forming, pickling, and finishing are found in the SMC bulletin “Fabricating”. Welding,
brazing, and soldering techniques are discussed in “Joining”. These bulletins are available on the website
www.specialmetals.com.
Available Products and Specifications
INCOLOY Alloy 825 is designated as UNS N08825 and Werkstoff Number 2.4858. It is listed in NACE MR0175 for oil and
gas service. Alloy 825 is available as pipe, tube, sheet, strip, plate, round bar, flat bar, forging stock, hexagon and wire.
Rod, Bar, Wire and Forging Stock - BS 3076NA16, ASTM B 425, ASTM B 564, ASME SB 425, ASME SB 564, ASME
Code Case N-572, DIN 17752, DIN 17753, DIN 17754, VdTÜV 432, ISO 9723, ISO 9724, ISO 9725
Plate, Sheet and Strip - BS 3072NA16, BS 3073NA16, ASTM B 424, ASTM B 906, ASME SB 424, ASME SB 906, DIN
17750, VdTÜV 432, ISO 6208
Pipe and Tube - BS 3074NA16, ASTM B 163, ASTM B 423, ASTM B 704, ASTM B 705, ASTM B 751, ASTM B 775,
ASTM B 829, ASME SB 163, ASME SB 423, ASME SB 704, ASME SB 705, ASME SB 751, ASME SB 775, ASME SB
829, ASME Code Case 1936, DIN 17751, VdTÜV 432, ISO 6207
Others - ASTM B 366, ASME SB 366, DIN 17744