INCONEL 718 TECHNICAL DATA


Type Analysis | Description | Physical Constants | Heat Treatment
Workability | Typical Mechanical Properties

Type Analysis

Element

Min

Max

Carbon

--

0.08

Manganese

--

0.35

Silicon

--

0.35

Phosphorus

--

0.015

Sulfur

--

0.015

Nickel + Cobalt

50.0

55.0

Chromium

17.0

21.0

Cobalt

--

1.00

Iron

Balance

Aluminum

0.35

0.80

Molybdenum

2.80

3.30

Titanium

0.65

1.15

Boron

0.001

0.006

Copper

--

0.15

Cb + Ta

4.75

5.50

Description

Alloy 718 is a precipitation hardenable nickel-based alloy designed to display exceptionally high yield, tensile and creep-rupture properties at temperatures up to 1300°F. The sluggish age-hardening response of alloy 718 permits annealing and welding without spontaneous hardening during heating and cooling. This alloy has excellent weldability when compared to the nickel-base superalloys hardened by aluminum and titanium. This alloy has been used for jet engine and high-speed airframe parts such as wheels, buckets, spacers, and high temperature bolts and fasteners.


Physical Constants

Density                                                                                  Electrical resistivity 
   lb/cu in .............................. 0.293                                       ohms-cir mil/ft ................................ 728
   kg/cu m .............................. 8220                                       microhm-mm ................................. 1210 
Melting Range
  °F ................................ 2200-2450
  °C .................................1210/1344

Modulus of Elasticity (E)

Temperature

psi x 10(6)

MPa x 10(3)

°F

°C

70
200
400
600
800
1000
1200
1400
1600
1750

21
93
204
316
427
538
649
760
871
954

29.6
29.2
28.8
27.6
26.5
25.5
24.5
23.1
18.1
11.1

208
205
202
194
186
179
172
162
127
78

Coefficient of Thermal Expansion

Temperature Range

10(-6)/°F

10(-6)/°C

77°F to

25°C to

200
400
600
800
1000
1200
1400

93
204
316
427
538
649
760

7.1
7.5
7.7
7.9
8.0
8.4
8.9

12.8
13.5
13.9
14.2
14.4
15.1
16.0


Heat Treatment

The following heat treatment should be used to obtain the best combination of tensile properties and stress rupture properties:
1 hr 1750°F to 1800°F (954 to 982°C) air cool + 8hr 1325°F (718°C) cool 100°F /hr to 1150°F (56 °C/hr to 621°C), hold 8 hrs and air cool.
To obtain the best room temperature and cryogenic tensile properties, the following heat treatment should be used:
1 to 2 hr 1950°F (1066°C), air cool + 8 hr 1325°F (718°C) cool 100°F/hr to 1150°F (56°C/hr to 621°C), hold 8 hr and air cool.


Workability

Hot Working
Hot-working is carried out using a 2050°F (1121°C) maximum furnace temperature. Hot-cold working in the range 1700/1850°F (927/1010°C) will improve the strength of the forging if the service temperature is below about 1100°F (593°C). Prolonged soaking at the forging temperature is not desirable. The material should be given uniform reductions to avoid the formation of duplex grain structures.

Machining
The alloy can be readily machined in either the annealed or the age-hardened condition. The age-hardened condition gives better chip action on chip breaker tools and produces a better finish. The annealed condition will give a slightly longer tool life.

Welding
Alloy 718 can be welded in either the annealed or the age condition. Welding in the aged condition will cause the formation of a softened heat-affected zone.


Typical Mechanical Properties

Elevated Temperature Tensile Tests
1/2" bar stock

Test
Temperature

0.2%
Yield Strength

Tensile
Strength

%
Elongation 2"

°F

°C

ksi

MPa

ksi

MPa

200
400
600
800
1000
1200
1400

93
204
316
427
538
649
760

170
163
159
156
155
149
110

1172
1124
1096
1076
1069
1027
758

204
198
195
191
185
168
110

1407
1365
1344
1317
1276
1158
758

21.0
20.0
20.0
19.0
18.0
19.0
27.0

Heat Treatment: 1 hr - 1800°F, air cool + 8 hr-1325°F, cool 100°F/hr to 1150°F, hold 8 hr, air cool.

Stress Rupture Data

Test
Temperature

Stress for Rupture

°F

°C

100 Hours

1000 Hours

Smooth

Notch

Smooth

Notch

ksi

MPa

ksi

MPa

ksi

MPa

ksi

MPa

1100
1200
1300
1400

593
649
704
760

170
110
75
44

1172
758
517
303

220
195
130
63

1517
1344
896
434

130
85
55
25

896
586
379
172

205
170
80
35

1416
1172
552
241

Heat Treatment: 1 hr - 1850°F, air cool + 8 hr - 1325°F, furnace cool to 100°F/hr to 1150°F, hold 8 hr, air cool.

Inconel 718 - Current Inventory Stock

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