Inconel 690 Alloy for Nuclear Power Plant & Energy Equipment

（High safety Inconel 690 material for nuclear energy systems. Stable performance under high temperature and radiation environment.）

In Pressurized Water Reactor (PWR) nuclear power plants and high-temperature corrosive energy systems, material failure is not an option. Inconel 690 (UNS N06690 / W.Nr. 2.4642)​ is a high-chromium (27–31%) austenitic nickel-iron-chromium alloy specifically developed to replace Inconel 600 in steam generator (SG) applications due to its inherent immunity to Primary Water Stress Corrosion Cracking (PWSCC) and superior resistance to caustic and acidic environments. Shanghai COCESS Special Alloys Co., Ltd​ supplies nuclear-grade and industrial-grade Inconel 690 plate, tube, bar, and forgings in strict accordance with ASTM B168, B166, B167, and ASME SB standards, with full traceability, low cobalt/copper control options, and third-party inspection (SGS / TÜV / DNV) for critical energy projects.

Chemical Composition & Metallurgical Advantage (vs. Alloy 600)

The defining feature of UNS N06690 is its ~30% Chromium content, nearly double that of early austenitic stainless steels and significantly higher than Alloy 600 (15–17% Cr). This promotes a tenacious, self-healing Cr₂O₃ passive film even in high-temperature deaerated water containing trace impurities (Cl⁻, OH⁻, O₂, F⁻).

Typical Chemistry (wt%, per ASTM B168 / ASME SB168 & RCC-M M3300 series):

• Nickel (Ni):​ 58.0 – 63.0 % (Balance / Matrix)

• Chromium (Cr):​ 27.0 – 31.0 % (Key: Forms robust Cr₂O₃ scale; eliminates PWSCC susceptibility)

• Iron (Fe):​ 7.0 – 11.0 % (Austenite stabilizer)

• Carbon (C):​ ≤ 0.05 % (Nuclear grade preferably ≤ 0.02 % to avoid sensitization)

• Manganese (Mn):​ ≤ 0.50 %

• Silicon (Si):​ ≤ 0.50 %

• Sulfur (S):​ ≤ 0.015 % (Premium nuclear grade ≤ 0.005 %)

• Copper (Cu):​ ≤ 0.50 %

• Cobalt (Co):​ ≤ 1.00 % (Often restricted to ≤ 0.05–0.10 % for activated corrosion product control in PWRs)

• Al + Ti:​ Usually ≤ 0.50 % total (Not a precipitation-hardening alloy; solid-solution strengthened)

Physical & Mechanical Properties (Solution Annealed Condition)

Inconel 690 is a solid-solution strengthened alloy—no aging treatment is required. It is typically supplied in the solution-annealed (1040–1150°C rapid quench) condition for optimum corrosion resistance and formability.

Physical Constants:

• Density:​ 8.19 g/cm³ (0.296 lb/in³)

• Melting Range:​ 1349 – 1446 °C (2460 – 2635 °F)

• Thermal Conductivity (20°C):​ ~12.8 W/m·K

• Coefficient of Thermal Expansion (20–1000°C):​ ~14.4 × 10⁻⁶ /K

• Magnetic:​ Non-magnetic in annealed condition

Typical Mechanical Properties (Room Temp, Solution Annealed):

• Tensile Strength (Rm):​ ≥ 620 MPa (90 ksi); typical 690–760 MPa

• Yield Strength (Rp0.2):​ ≥ 275 MPa (40 ksi); typical 300–345 MPa

• Elongation (A5):​ ≥ 35 % (typical 40–45 % — excellent ductility for U-bending & expansion)

• Hardness:​ ≤ 100 HRB (≤ 220 HB)

• Service Temperature:​ Continuous use from cryogenic to ~1100°C in oxidizing atmosphere; in PWR primary side ~290–330°C.

Nuclear & Energy-Specific Performance Characteristics

• Immunity to PWSCC (Primary Water Stress Corrosion Cracking):​

  Extensive IGSCC and PWSCC testing confirms Inconel 690 is essentially immune to intergranular SCC in PWR primary water (320°C, 1500–2000 ppm B as H₃BO₃, 2–4 ppm Li as LiOH) due to the absence of Cr-depleted zones along grain boundaries—even after long-term service exposure.

• Resistance to Caustic SCC & Intergranular Attack:​

  In concentrated NaOH/KOH environments (secondary side crevices), 690 outperforms 600. Its high Cr content suppresses alkali-induced SCC and localized attack.

• Low Uniform Corrosion & FAC Resistance:​

  In once-through steam generator (OTSG) or recirculating SG environments, uniform corrosion rates are extremely low (< 0.1 mil/year), and Flow-Accelerated Corrosion (FAC) susceptibility on the secondary side is manageable with proper pH control.

• Radiation Stability & Low Cobalt Option:​

  For nuclear applications, Co can be controlled to ≤ 0.05 % to minimize production of Co‑60 activated corrosion products, reducing radiation field buildup during outages.

Product Forms & Typical Applications in Nuclear & Energy Sectors

Shanghai COCESS Special Alloys Co., Ltd​ stocks and processes Inconel 690 in the following forms:

Optional: Inner Surface Shot Peening (ISP) simulation capability for tube stock, 100% Eddy Current Testing (ET) / Ultrasonic Testing (UT), hydrostatic test per customer spec.

Quality Assurance for Nuclear-Grade Material

Every order from Shanghai COCESS Special Alloys Co., Ltd​ is shipped with:

• EN 10204 3.1 Mill Test Report:​ Including heat analysis, mechanical results, grain size report, and heat treatment record.

• Dimensional & Visual Inspection:​ Verified per order drawing / standard.

• NDE Options:​ 100% ET/UT on tubes, PT/MT on plates & forgings, hydraulic/pneumatic leak test.

• Elemental Control:​ Low S, low Co, low gas (O/N/H) options for nuclear specifications.

• Third-Party Witness:​ SGS, TÜV, DNV, BV, ABS available upon request.

For Inconel 690 plate, tube (including SG U-tube stock), bar, or clad strip — including current inventory, sample MTR, nuclear technical questionnaire response, or a formal quotation — please contact Shanghai COCESS Special Alloys Co., Ltd. Our technical team understands the additional documentation, elemental restrictions, and NDT rigor required for nuclear power and high-reliability energy equipment supply chains.

Website: https://en.cocessalloys.com
Email: sales@cocessalloys.com