Scope

This specification covers hot- and cold-worked precipitation-hardenable nickel alloy rod, bar, forgings, and forging stock for moderate or high temperature service (Table 1).
The values stated in inch-pound units are to be regarded as standard, The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

Chemical Composition

The material shall conform to the requirements as to chemical composition prescribed in Table 1.
If a product (check) analysis is performed by the purchaser, the material shall conform to the product (check) analysis variations prescribed in Specification B880.

Element Composition Limits, %
UNS N07718 (Formerly Grade 718)
Carbon 0.08 max
Manganese 0.35 max
Silicon 0.35 max
Phosphorus 0.015 max
Sulfur 0.015 max
Chromium 17.0-21.0
Cobalt 1.0 maxA
Molybdenum 2.80-3.30
Columbium (Nb) + tantalum 4.75-5.50
Titanium 0.65-1.15
Aluminum 0.20-0.80
Boron 0.006 max
Iron remainderB
Copper 0.30 max
Nickel 50.0-55.0
Note:

A. If determined.
B. The element shall be determined arithmetically by difference.

Mechanical Properties

1) Unless otherwise specified, the material shall be supplied in the cold worked or solution treated condition, suitable for subsequent age hardening.
The cold worked or solution treated material shall be capable of meeting the mechanical property requirements of Table 3, and the stress rupture lequirements of Table 4 (except alloys UNS N07022, N09925 and N07725), following the precipitation hardening treatment described in Table 2.
3) When the material is to be supplied in the cold worked or solution treated plus aged condition, the requirements of Table 3 and Table 4 (except alloys UNS N07022, N09925 and N()7725) shall apply, with the precipitation hardening treatment of Table 2, or as agreed upon between the purchaser and the manufacturer as part of the purchase contract,

Heat Treatment

Alloy Recommended
Annealing Treatment
Recommended Solution
Treatment
Recommended Stabilizing
Treatment
Precipitation Hardening
Treatment
N07718 ... 1700 to 1850°F (924 to 1010°C), hold 1/2 h min, cool at rate equivalent to air cool or faster. ... 1325 ± 25 °F (718 ± 14°C), hold at temperature for 8 h, furnace cool to 1150 ± 25 °F (621 ± 14°C), hold until precipitation heat treatment time has reached 18 h, air cool.

Tensile and Hardness RequirementsA

Alloy Heat Treatment Tensile Strength, min, psi [MPa] Yield Strength (0.2 % offset), min, psi [MPa] Elongation in 2 in. [50 mm] or 4D, min, % Reduction of Area, min, % Brinell Hardness
N07718 solution + precipitation harden 185 000 [1275] 150 000 [1034] 12 [6]E 15 [8]E 331 min
Note:

A. The supplier shall demonstrate that the material will meet fully heat-treated properties after full heat treatment in accordance with Table 2.
B. Forgings.
C. Up to 2.50 in. [63.5 mm], exclusive.
D. 2.50 to 4.00 in. [63.5 to 101.6 mm], exclusive.
E. These values apply for tension specimens machined tangentially from near the center of large disk forgings over 50 in.2 [3225.8 mm2] in cross section or radially from rings 3 in. [76.2 mm] or more in thickness.
F. Cold worked, solution annealed and aged, 0.625 in. [15.9 mm] to 3 in. [76.2 mm], inclusive.
G. Hot worked, solution annealed and aged, 1 in. [25.4 mm] or over.

Stress Rupture Requirements

Alloy Heat Treatment Test
Treatment
F(C)
Stress, psi
(MPa) B
Minimum Hours Elongation in 2 in. or 50mm(or 4D), min,%
N07718 solution + precipitation harden. 1200
(649)
100000
(690)
23 5

Number of Tests

Chemical Analysis—One test per lot.
Tension—One test per lot,
Hardness—One test per lot.
Stress-Rupture—One test per lot.

Test Methods

Determine the chemical composition and mechanical and other properties of the material as enumerated in this specification, in case of disagreement, in accordance with the following methods:

Test ASTM Desigination
Chemical Analysis E1473
Tension E8/E8M
Rounding Procedure E29
Stress-rupture E139
Hardness Conversion El 40

For purposes of determining compliance with the specified limits for requirements of the properties listed in the following table, an observed value or a calculated value shall be rounded in accordance with the rounding method of Practice E29,

Test Rounded Unit for Observed Or Calculated Value
Chemical composition, Nearest unit in the last righthand place of figures of the pressed in decimals), specified limit. If choices and hardness Nearest unit in the last righthand place of figures of the pressed in decimals), specified limit. If choices and hardness are possible, as when the digits dropped are exactly a 5 or a 5 followed only by zeros, choose the one ending in an even digit, with zero defined as an even digit.
Tensile strength and yield strength Nearest 1000 psi (6.9 MPa)
Elongation Nearest 1%
Rupture life 1h

Certification

When specified in the purchase order or contract, a producer's or supplier's certification shall be furnished to the purchaser that the material was manufactured, sampled, tested, and inspected in accordance with this specification and has been found to meet the requirements. When specified in the purchase order or contract, a report or the test results shall be furnished.

Referenced Documents

Standard Documents
B880 Specification for General Requirements for Chemical Check Analysis Limits for Nickel, Nickel Alloys and Cobalt Alloys
E8/E8M Test Methods for Tension Testing of Metallic Materials
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
El 39 Test Methods for Conducting Creep, Creep-Rupture, and Stress-Rupture Tests of Metallic Materials
El 4() Hardness Conversion Tables for Metals Relationship Among Brinell Hardness, Vickers Hardness, Rockwell Hardness, Superficial Hardness, Knoop Hardness, Scleroscope Hardness, and Leeb Hardness
E 1473 Test Methods for Chemical Analysis of Nickel, Cobalt and High-Temperature Alloys