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Nickel Alloy 686, designated under the UNS N06686, is a remarkable material that stands out due to its exceptional physical and chemical properties. It is specifically engineered to perform under high-stress conditions and is widely recognized for its excellent resistance to chemical corrosion and high-temperature environments.

Physical Properties in the Annealed Condition

Nickel Alloy 686 maintains its impressive properties over a temperature range from -20°F to +100°F. When in the annealed condition, it showcases substantial tensile and yield strengths, making it an ideal choice for demanding applications. The tensile strength of Alloy 686 is approximately 100,000 psi (690 MPa) which translates to about 100 ksi. This strength is complemented by a yield strength of 45,000 psi (310 MPa) or 45 ksi.

The elongation of Nickel Alloy 686 is a minimum of 45% in 2 inches, indicating significant ductility which is beneficial in applications needing deformation without fracture. The alloy boasts a modulus of elasticity of 30 x 10^6 psi, allowing it to withstand significant tensile stresses without deformation. Furthermore, it has a mean coefficient of thermal expansion of 6.7 IN./IN./°F x 10^-6, and a thermal conductivity of 118 BTU-in/ft^2-h-°F, making it an efficient conductor of heat.

Chemical Composition and Structural Integrity

Nickel Alloy 686 is predominantly composed of nickel, ensuring robustness and resistance to a wide array of corrosive environments. Its chromium content ranges between 19.0% to 23.0%, providing excellent oxidation resistance. The alloy also comprises molybdenum (15.0% to 17.0%), contributing to its strength and corrosion resistance, particularly in reducing environments.

The inclusion of up to 4.40% tungsten enhances its high-temperature strength and provides resistance against pitting and crevice corrosion. With minimal iron content (maximum 5.0%) and controlled amounts of elements like manganese and silicon, the alloy maintains its structural stability without compromising its corrosion resistance.

Industry Applications and Standards

Nickel Alloy 686 is highly sought after in industries such as chemical processing, pollution control, and oil and gas due to its resilience in harsh environments. It is primarily supplied in the form of tubing and piping, conforming to specifications such as ASTM B619 and B626. These standards ensure that the material meets the necessary criteria for pressure vessel and piping applications, providing assurance of its performance and reliability.

Its designation as Werkstoff NR. 2.4606 further cements its place within globally recognized standards, ensuring interoperability and compliance across various industrial applications. Additionally, the material must adhere to stringent specifications set by ASTM and ASME, ensuring it meets the rigorous demands of high-stress environments.

Conclusion

Nickel Alloy 686 is a durable, corrosion-resistant material designed to withstand extreme conditions while maintaining structural integrity and high performance. Its balanced chemical composition and robust physical properties make it a preferred choice across a variety of industries requiring materials that offer both strength and corrosive resistance under severe environmental conditions. Whether in chemical processing or high-temperature industrial applications, Nickel Alloy 686 continues to meet and exceed industry standards, making it an indispensable asset in advanced engineering solutions.