Nickel Alloy Inconel 690-TT (Thermally treated)
Heat-treated state
UNS N06690 · EN 2.4642, NiCr29Fe
Nuclear steam-generator tubing condition (Alloy 690TT) giving maximum resistance to primary-water and caustic SCC.
Values for the TT condition
Other Inconel 690 tempers and conditions
Inconel 690 is listed in 7 conditions; see the grade overview at Inconel 690.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
TTThis page Thermally treated | Nuclear steam-generator tubing condition (Alloy 690TT) giving maximum resistance to primary-water and caustic SCC. | 320 | 700 | 45 | 165 HB | — |
ANNDefault Annealed | Standard stocked condition for plate, sheet, bar and tube — best ductility, formability and corrosion resistance. | 345 | 725 | 45 | 170 HB | — |
Hot worked / hot finished | Economical condition for heavy bar, forgings and rings where the hot-finished properties satisfy ASTM B166 minima. | 400 | 760 | 38 | 190 HB | — |
Quarter-Hard | Light cold work for slightly higher yield strength while keeping useful bending ductility in strip and tube. | 550 | 800 | 28 | 17 HRC | 1.5 % IACS |
Cold drawn + stress relieved | Cold-drawn bar/tube with residual stresses reduced for dimensional stability and lower SCC risk while keeping most cold-work strength. | 690 | 880 | 20 | 22 HRC | 1.5 % IACS |
Half-Hard | Springy strip, wire and thin-wall tube needing roughly double the annealed yield strength. | 700 | 900 | 18 | 24 HRC | — |
Full-Hard | Maximum as-drawn strength for springs, fasteners and small-diameter wire; very limited ductility and no recrystallization above ~550 °C service. | 900 | 1,070 | 8 | 32 HRC | — |
What is Inconel 690-TT?
Inconel 690-TT is Inconel 690 heat treated to TT — nuclear steam-generator tubing condition (Alloy 690TT) giving maximum resistance to primary-water and caustic SCC. Inconel 690-TT has a yield strength of 320 MPa (46.4 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 69% of nickel alloy grades. Elongation at break is 45% and the elastic modulus is 211 GPa (30.6 Msi). Inconel 690-TT has a density of 8.19 g/cm³ (0.296 lb/in³), lighter than 68% of nickel alloy grades. It melts at 1,343°C (2,449 °F). ANN is the default condition FabDigit quotes; TT is available on request or by drawing note.
Advantages
- Tough — resists crack growth — 200 MPa·√m (182 ksi·√in), better than 99% of nickel alloy grades
- Good corrosion resistance — 92/100, better than 91% of nickel alloy grades
Limitations
- Limited service temperature — 400°C (752 °F), worse than 94% of nickel alloy grades
Inconel 690-TT properties
Typical room-temperature values for Inconel 690-TT; 10 are specific to this condition. Other listed values are Inconel 690 reference data and may not represent this condition. Bars are the position among nickel alloy grades.
Physical3
Inconel 690-TT has a density of 8.19 g/cm³ (0.296 lb/in³), lighter than 68% of nickel alloy grades. It melts at 1,343°C (2,449 °F).
Mechanical16
Inconel 690-TT has a yield strength of 320 MPa (46.4 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 69% of nickel alloy grades. Elongation at break is 45% and the elastic modulus is 211 GPa (30.6 Msi).
Thermal6
Inconel 690-TT is rated for continuous service to 400°C (752 °F). It conducts heat at 13.5 W/m·K (7.8 BTU/hr·ft·°F), better than 73% of nickel alloy grades. Thermal expansion is 14 µm/m·K (7.78 µin/in·°F).
Electrical3
Inconel 690-TT conducts electricity at 1.5 % IACS, better than 59% of nickel alloy grades.
Chemical & Environmental3
Corrosion resistance is excellent (92/100), better than 91% of nickel alloy grades.
Sustainability4
Producing a kilogram of Inconel 690-TT takes about 135 MJ of energy and emits 13.5 kg of CO₂ — less than 84% of nickel alloy grades. Typical recycled content is 40%.
Manufacturability8
Inconel 690-TT's machinability is poor (25/100, better than 76% of nickel alloy grades); weldability very good (78/100); formability good (68/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Inconel 690-TT
Is Inconel 690 easy to machine?
Treat like a gummy austenitic superalloy: rigid setups, positive-rake sharp carbide or ceramic tools, heavy constant feed to cut under the work-hardened layer, low SFM and copious high-pressure coolant.
Can Inconel 690 be welded?
Readily GTAW/GMAW/SMAW welded without preheat or PWHT; use matching ERNiCrFe-7/7A or ERNiCr-3 style high-Cr fillers, keep interpass temperature low and heat input modest to avoid hot cracking.
Can Inconel 690 be formed, bent or molded?
Cold forms well in the annealed temper but work-hardens fast — allow extra power, generous radii and intermediate anneals at 1040–1090 °C; hot work at 1090–1230 °C with finishing above ~950 °C.
What surface finishes work on Inconel 690?
Pickle or grind off the tenacious chromium oxide before welding and before any brazing/plating; electropolishing or fine mechanical polishing gives the low-crud surfaces required for nuclear service.
Inconel 690 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Ni58 % minimum per ASTM B168 | ≥ 58 | 60 |
| Cr | 27 – 31 | 29 |
| Fe | 7 – 11 | 9.5 |
| C0.015–0.025 typical for TT nuclear tubing | ≤ 0.05 | 0.02 |
| Mn | ≤ 0.5 | 0.2 |
| Si | ≤ 0.5 | 0.3 |
| Cu | ≤ 0.5 | 0.02 |
| S | ≤ 0.02 | 0 |
| Tispecified in nuclear tubing orders | ≤ 0.5 | 0.25 |
| Alsupplementary/producer limit | ≤ 0.5 | 0.2 |
Inconel 690-TT — frequently asked
What is Inconel 690-TT used for?
Inconel 690-TT is typically used for nuclear steam generator tubing, pressurised water reactor primary-side components, reactor vessel head penetrations and nozzles, tube plugs and sleeves, nuclear waste vitrification melter parts and nitric and mixed-acid process equipment. In short: nuclear-grade SCC resistance; high-Cr upgrade of Alloy 600; good weldability, poor machinability.
What is the yield strength of Inconel 690-TT?
Inconel 690-TT has a typical yield strength of 320 MPa (46.4 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 69% of nickel alloy grades. Strength varies by condition: see the 7 listed tempers.
Is Inconel 690-TT easy to machine?
Not especially — machinability is rated poor (25/100, better than 76% of nickel alloy grades). Treat like a gummy austenitic superalloy: rigid setups, positive-rake sharp carbide or ceramic tools, heavy constant feed to cut under the work-hardened layer, low SFM and copious high-pressure coolant.
Can Inconel 690-TT be welded?
Yes — weldability is rated very good (78/100). Readily GTAW/GMAW/SMAW welded without preheat or PWHT; use matching ERNiCrFe-7/7A or ERNiCr-3 style high-Cr fillers, keep interpass temperature low and heat input modest to avoid hot cracking.
What surface finishes work on Inconel 690-TT?
Pickle or grind off the tenacious chromium oxide before welding and before any brazing/plating; electropolishing or fine mechanical polishing gives the low-crud surfaces required for nuclear service.
Can Inconel 690-TT be formed, bent or molded?
Cold forms well in the annealed temper but work-hardens fast — allow extra power, generous radii and intermediate anneals at 1040–1090 °C; hot work at 1090–1230 °C with finishing above ~950 °C.
What is the maximum service temperature of Inconel 690-TT?
Inconel 690-TT is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Inconel 690-ANN and Inconel 690 CW-FH?
ANN is the default condition — standard stocked condition for plate, sheet, bar and tube — best ductility, formability and corrosion resistance. CW-FH: maximum as-drawn strength for springs, fasteners and small-diameter wire; very limited ductility and no recrystallization above ~550 °C service. Yield strength is 345 MPa in ANN versus 900 MPa in CW-FH.
Sources
- INCONEL alloy 690 technical bulletin — Special Metals Corporation (2009)
- ASTM B168 — Ni-Cr-Fe alloy plate, sheet and strip — ASTM International (2019)
- ASTM B166 — Ni-Cr-Fe alloy rod, bar and wire — ASTM International (2019)
- ASME SB-163 / SB-167 (N06690 tubing, incl. thermally treated) — ASME (2021)
- GB/T 15007 / NS3105 (2017)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.