ZYTC Inconel® 690 (UNS N06690) Nickel-Chromium-Iron Alloy 

I. Product Information

• Material Name: Inconel® 690 Nickel-Chromium-Iron Alloy (UNS N06690)
• Material Definition: A nickel-chromium-iron alloy specifically engineered with high chromium content (approximately 29%)—among the highest of any nickel-based alloy commonly used for pressure equipment fabrication. This elevated chromium level provides superior resistance to oxidation, sulfidation, and nitridation.
• Core Value Proposition: Exceptional resistance to stress-corrosion cracking (SCC) in high-purity water and caustic environments, combined with outstanding high-temperature stability in oxidizing, sulfur-bearing, and nitrogen-bearing atmospheres.
• Key Metallurgical Advantages:
  • High Chromium (27-31%): Forms a stable, protective chromium oxide layer
  • Low Carbon (0.05% max): Minimizes carbide precipitation and maintains corrosion resistance
  • Not Hardenable by Heat Treatment: Used in solution-annealed condition for optimal corrosion resistance and fabricability
  • Superior SCC Resistance: Particularly in nuclear-grade high-purity water and caustic environments
• Certification & Quality: ISO 9001 and AS9120 certified, ensuring full traceability and compliance.
• Product Forms Available from ZYTC:
  • Bar & Rod | Plate, Sheet & Strip | Pipe & Tube (Seamless)
  • Forgings | Wire | Custom Fabricated Components

II. Material Standards & Specifications

III. Chemical Composition (wt%)

The defining characteristic of Inconel 690 is its high chromium content, which provides exceptional corrosion and oxidation resistance.

*Note: The combination of high chromium (27-31%) and low carbon (0.05% max) is critical for resistance to sensitization and stress-corrosion cracking.*

IV. Service Conditions & Material Selection Boundaries

Suitable Conditions (Why choose it?)

1. High-Purity Water Environments: Exceptional resistance to stress-corrosion cracking (SCC) in nuclear reactor coolant systems, steam generators, and associated piping.
2. Caustic Environments: Outstanding performance in concentrated caustic solutions at elevated temperatures.
3. Oxidizing High-Temperature Atmospheres: Superior resistance to oxidation due to stable chromium oxide layer formation.
4. Sulfidizing and Nitriding Environments: High chromium content provides excellent resistance to sulfur and nitrogen compound attack at elevated temperatures.
5. Mixed Acid Environments: Good performance in various high-temperature aqueous media with low corrosion rates.

Typical Applications:

• Nuclear Power Systems: Steam generator tubing, core support structures, reactor internals, control rod drive mechanisms
• Thermal Waste Treatment: Incinerator components, radioactive waste vitrification equipment, coal gasification units
• Chemical Processing: Furnace components, baffles, burners for petrochemical processing; ducts and reheaters for sulfuric and nitric acid production
• Pollution Control: Tail-gas reheaters in nitric acid plants, flue gas handling equipment

Material Selection Boundaries (When to consider alternatives?)

• Reducing Acid Environments: For strong reducing acids like hydrochloric, consider Inconel 625 or Hastelloy C-276
• Pitting/Crevice Corrosion: For environments requiring maximum resistance to localized corrosion, consider Inconel 625 or 686
• Extreme High-Temperature Creep (>1000°C): For applications requiring long-term creep resistance above 1000°C, consider Inconel 601 or 602 CA
• High-Strength Requirements: If higher mechanical strength is needed, consider precipitation-hardened alloys like Inconel 718

V. Manufacturing Process & Heat Treatment

Heat Treatment Process Parameters:

Fabrication Guidelines:

• Hot Working: Recommended temperature range: 1040°C - 1230°C (1900°F - 2250°F) for heavy forming. Light forming possible down to 870°C (1600°F). Avoid working in low-temperature range.
• Cold Working: Can be formed using conventional methods. Work-hardens rapidly; intermediate annealing may be required for severe deformation.
• Machining: Requires rigid tooling, positive feeds, and sharp cutting edges due to work-hardening characteristics. Similar to other nickel-based alloys.
• Welding: Excellent weldability using GTAW/TIG and SMAW/Stick processes. Use matching filler metals (ERNiCrFe-7) and electrodes (ENiCrFe-7) to maintain corrosion resistance in weld zone. No pre-heat generally required.

VI. Mechanical Properties (Typical Values)

Note: Properties shown are for solution-annealed condition. Contact our technical team for certified test reports specific to your product form.

VII. Material Comparison & Selection Guide

This comparison aids in selecting between Alloy 690 and other relevant alloys for nuclear and high-temperature applications.

Procurement Recommendation:

• Choose Inconel 690 for nuclear steam generator tubing, high-purity water systems, and environments requiring exceptional SCC resistance combined with high-temperature oxidation resistance. Its high chromium content makes it the preferred choice for oxidizing, sulfidizing, and nitriding atmospheres.
• Choose Inconel 600 for a cost-effective solution for general high-temperature service and caustic environments where the extreme SCC resistance of 690 is not required.
• Choose Inconel 625 when you need a combination of high strength and exceptional resistance to both aqueous corrosion and high-temperature environments.
• Choose 304/316 Stainless Steel for cost-sensitive applications in less aggressive environments where the superior properties of nickel alloys are not justified.

Request a Quote or Sample Today:

If your nuclear, chemical processing, or waste treatment applications demand the proven SCC resistance and high-temperature stability of Alloy 690, contact the ZYTC Alloy sales team today. We provide certified materials, technical expertise, and reliable global logistics.

Contact us to request a free sample and a competitive quote. Our technical team is ready to assist with material selection and application support.

Contact Us:

Email:daisy@zytcsteel.com

WhatsApp/WeChat: +86 17335753350