Nickel Alloys In Petrochemical and Refining Corrosive Environments

The petrochemical and refining industry involves processing crude oil and natural gas into a wide range of chemical products - fuels, lubricants, ethylene, ammonia, plastics, synthetic fibers, rubber, detergents, solvents, as well as raw materials used in pharmaceuticals and cosmetics. In Poland, the largest refineries are located in Płock and Gdańsk.

Many processes operate at elevated temperatures (400–1000°C) and in highly corrosive environments. At different stages, equipment is exposed to aggressive atmospheres containing compounds of oxygen, carbon, nitrogen, sulfur, and chlorine. High temperatures and pressures also demand excellent creep resistance and mechanical strength. For this reason, components such as bolts, fans, valves, reactors, piping, transmission pipelines, and pumps are commonly made from nickel-based alloys. The most suitable grade depends on the specific operating conditions and challenges.

Nickel Alloys Used in Petrochemical Industry

Alloy 800H and 800HT are standard choices for intermediate-temperature applications (620–925°C). They are used in hydrogen reformers, ethylene dichloride furnace tubes, pipelines, and high-temperature pressure vessels. These are cost-effective alloys with a high iron content.

Alloy 600 and Alloy 625 are used in halide environments.

Alloy 601 and Alloy 600 are used in high-temperature oxidizing applications.

Alloy 617 and Alloy 600 are designed for service in strongly carburizing and nitriding environments.

Alloy 617 and Alloy 625 are also used in expansion joints that require high fatigue resistance.

Oxidation Resistance - Oxidation rate in flowing air during 25-hour thermal cycles at 1095°C:

• Alloy 600 – 1.55 mm/year
• Alloy 617 – 2.24 mm/year
• Alloy 601 – 2.49 mm/year
• Alloy 800H – 3.40 mm/year
• Alloy 625 – 3.45 mm/year

Carburization Resistance - Carbon absorption after 24 hours in an Ar–5H₂–5CO–5CH₄ atmosphere at 1090°C:

• Alloy 600 – 9.9 mg/cm²
• Alloy 625 – 9.9 mg/cm²
• Alloy 617 – 11.5 mg/cm²
• Alloy 800H – 12.6 mg/cm²

Nitriding Resistance - Nitrogen absorption after 168 hours in ammonia at 1090°C:

• Alloy 600 – 0.2 mg/cm²
• Alloy 617 – 1.9 mg/cm²
• Alloy 601 – 2.6 mg/cm²
• Alloy 625 – 3.3 mg/cm²
• Alloy 800H – 5.5 mg/cm²

Resistance to Halides (Chlorine Compounds) - Mass loss after scale removal following 500 hours at 705°C:

• Alloy 600 – 97 mg/cm²
• Alloy 625 – 180 mg/cm²
• Alloy 617 – 190 mg/cm²
• Alloy 601 – 215 mg/cm²
• Alloy 800 – 890 mg/cm²

Fatigue Resistance - Rupture stress after 1,000 hours at 650°C:

• Alloy 625 – 370 MPa
• Alloy 617 – 360 MPa
• Alloy 800 – 165 MPa