Nickel is a versatile metal element, which can mix with various metals to yield valuable nickel alloys. Nickel alloys are non-ferrous metals possessing high strength and toughness. They show superior corrosion resistance and have excellent elevated temperature properties. Nickel alloy 625 (UNS N06625) is a popular nickel-chromium alloy known as Inconel® 625. It is highly valuable for its high strength, excellent fabricability, and adequate corrosion resistance.
Nickel Alloy 625 Composition
The chemical composition of nickel alloy 625 tubing includes:
- Nickel: 58.00 min
- Chromium: 20.0-23.0
- Molybdenum: 8.0-10.0
- Iron: 5 min
- Columbium and Tantalum: 3.15-4.15
- Cobalt: 1 .00 max
- Manganese: 0.50 max
- Silicon: 0.50 max
- Aluminum: 0.40 max
- Titanium: 0.40 max
- Carbon: 0.10 max
- Sulfur: 0.015 max
- Phosphorus: 0.015 max
Uses Of Nickel Alloy 625
Nickel alloy 625 is helpful in the following applications:
- Oceanographic equipment
- Nuclear reactor cores and control-rod components
- Combustion system transition liners
- Aircraft ducting systems, engine exhaust systems, and thrust-reverser systems
- Rings and tubing for environmental control systems
- Wire rope for mooring cables
- Propeller blades for motor patrol gunboats
- Meets ASME code for Boiler and Pressure Vessels
Exceptional Material Strength
In the nickel-chromium alloy base, the stiffening combination of molybdenum and niobium provides Inconel 625 with its high strength. The interaction of niobium with molybdenum strengthens the alloy matrix without any requirement for precipitation-hardening treatment. The superalloy has a tensile strength of 690 MPa and possesses a yield strength of 275 MPa.
Inconel 625 shows outstanding and versatile corrosion resistance under various temperatures and pressures. Hence, it is highly suitable for the chemical processing field. The unique composition of Inconel 625 optimizes its corrosion resistance capabilities. It also shows resistance to stress cracking and excellent pitting resistance in 500°-600°F (260-316°C) water. The superalloy is suitable for use in saline seawater and milder environments like fresh water and standard atmospheric conditions. When exposed to oxidizing agents, the nickel-chromium alloy matrix protects the superalloy. Molybdenum offers protection against pitting corrosion.
The thermal expansion coefficient of Inconel 625 at 20°C is 1.28 x 10-5 1/K, and it has a melting point of about 1300°C. The superalloy can resist cryogenic to extremely high temperatures. In 15% sulfuric acid, the superalloy undergoes corrosion at a minimal rate of 0.188 mm per year. When exposed to oxidizing agents at high temperatures, the titanium, and niobium compositions of the oxide film on the superalloy drastically increase to form a protective covering on the material.
Nickel alloy 625 shows excellent fabricability. Due to its ease of fabrication, it is generally helpful in making various components for plant equipment. Inconel 625 can retain high strength at elevated temperatures and can resist deformation at hot-working temperatures. You can quickly fabricate it by hot forming, provided that you use powerful equipment. The composition of the alloy gives it better weldability than earlier alloys. It does not crack on exposure to strain and temperature changes post-welding. Because of its high creep resistance and yield strength, it is suitable for tubing, piping, and plant equipment that needs welding.
These are a few essential aspects of Inconel 625. The combination of elements in the superalloy significantly augments its essential properties and makes it worthwhile across various industries.