Spreadsheet version
An always up-to-date spreadsheet with composition, heat treatment, and mechanical properties can be obatined HERE.
Heat treatment procedures
The UNS N07718 heat treatment procedures to obtain NA718 class 120K or 140K are described below,[1]
| Solution annealing | Age Hardening a | |||
|---|---|---|---|---|
| UNS | Material Designation | Material temperature | Time | Material temperature and Time |
| N07718 | 120K | 1021 to 1052 °C | 1 to 2.5h | 774 to 802°C for 6 to 8h |
| N07718 | 140K | 1021 to 1052 °C | 1 to 2.5h | 760 to 802°C for 6 to 8h |
b Cool in air, inert gas, water, polymer or oil to ambient temperature.
Mechanical properties
The required mechanical properties of UNS N07718 class 120K and 140K are described below, YS means yield strength and TS tensile strength. [1]
| UNS | Material Designation | Section thickness | 0.2% YS Min., ksi (MPa) | 0.2% YS Max., ksi (MPa) | TS, ksi (MPa) | Elongation | Reduction of area Min. |
|---|---|---|---|---|---|---|---|
| N07718 | 120K | < 254 mm | 120 (824) | 145 (1000) | 150 (1034) | 20% | 35% |
| N07718 | 120K | > 254 mm | 120 (824) | 145 (1000) | 150 (1034) | 20% | 25% |
| N07718 | 140K | < 254 mm | 140 (965) | 150 (1034) | 165 (1138) | 20% | 35% |
| N07718 | 140K | > 254 mm | 140 (965) | 150 (1034) | 165 (1138) | 20% | 25% |
Impact toughness
The required impact toughness of UNS N07718 class 120K and 140K are described below,[1]
| UNS | Material Designation | Section thickness | Orientation | Minimum. Average, ft-lbs (J) | TMinimum Single, ft-lbs (J) | Lateral expansion, in (mm) |
|---|---|---|---|---|---|---|
| N07718 | 120K | < 76 mm | Longitudinal | 50 (88) | 45 (61) | 0.015 (0.38) |
| N07718 | 120K | ≥ 76—254 mm | Transverse | 35 (47) | 30 (41) | 0.015 (0.38) |
| N07718 | 120K | > 254 mm | Transverse | 30 (41) | 27 (37) | 0.015 (0.38) |
| N07718 | 140K | < 76 mm | Longitudinal | 50 (88) | 45 (61) | 0.015 (0.38) |
| N07718 | 140K | ≥ 76—254 mm | Transverse | 35 (47) | 30 (41) | 0.015 (0.38) |
| N07718 | 140K | > 254 mm | Transverse | 30 (41) | 27 (37) | 0.015 (0.38) |
Hardness
The hardness limits of class 120K and 140K UNS N07718 are described below, [1]
| UNS | Material Designation | Minimum Hardness, HRC (HBW) | Maximum Hardness, HRC (HBW) |
|---|---|---|---|
| N07718 | 120K | 32 (a) | 40 (a) b |
| N07718 | 140K | 34 (a) | 40 (a) b |
a The conversion of hardness readings to or from other scales is material-dependent. Rockwell C scale is the preferred hardness method for hardness testing the family of alloys covered by API 6ACRA since compliance with ISO 15156 (ANSI/NACE MR0175) is frequently required, and ISO 15156 (ANSI/NACE MR0175) specifies the maximum acceptable hardness limits using the Rockwell C scale.[2] When conversions from other hardness scales to the Rockwell C scale are required or vice versa, one of two methods shall be used:
- Hardness conversion agreed to by the equipment manufacturer and the end user
- ASTM E140 conversion.
When a conflict exists between Rockwell C scale hardness numbers and Brinell hardness numbers, the Rockwell C scale shall be the referee method.
When a conversion other than the ASTM E140 conversion is utilized, the conversion method shall be documented and traceable to test results.
In accordance with ASTM E140, when reporting converted hardness numbers, the measured hardness and test scale shall be reported in parentheses. For example, 20.0 HRC (228 HBW), where 20.0 HRC is the converted hardness value and 228 HBW is the original measurement value and test scale.
b Maximum hardness limits shall be in accordance with ISO 15156 (ANSI/NACE MR0175).
More information
UNS N07718 chemical composition is described in this post.
References
- API 6ACRA, “Age-hardened Nickel-based Alloys for Oil and Gas Drilling and Production Equipment” (Houston, TX: American Petroleum Institute, 2015).↩
- ISO 15156, “Petroleum and natural gas industries – Materials for use in H2S-containing environments in oil and gas production.” (Geneva, Switzerland: International Organization for Standardization, 2015).
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