Alloy 602 CA - High Temperature and High Pressure Resistant

Alloy 602 CA is a high-temperature alloy material that exhibits excellent creep and oxidation resistance at temperatures up to 1200°C (2192°F). The alloy is supplied in the solution-annealed condition, with the surface being either oxidized or descaled.

Chemical Composition:

Material Characteristics

The features of this alloy in the solution-annealed condition (Grade 1) are:

• Excellent high-temperature creep strength

• Outstanding oxidation resistance, even under high-temperature cyclic conditions

• Excellent corrosion resistance in carburizing and oxidizing/chlorinating environments

• Certified for pressure vessel fabrication within the following temperature ranges, depending on the pressure vessel code:

  - TÜV Material Data Sheet 540: -10°C to 1150°C (14°F to 2102°F)

  - ASME Pressure Vessel Code Section I: Up to 899°C (1650°F), with applications up to 982°C (1800°F) per ASME VIII Div. I

Microstructural Characteristics

Alloy 602 CA has a face-centered cubic crystal structure. The precipitation of primarily M23C6 or M7C3 carbides provides good mechanical properties at high temperatures, especially above 1000°C (1832°F). Additionally, the formation of a γ-phase can occur at temperatures below 800°C (1472°F).

Mechanical Properties

The following are the properties of Alloy 602 CA in the solution-annealed condition within the specified size ranges:

• Plate ≤ 50 mm (≤ 1.97 in)

• Strip ≤ 3 mm (≤ 0.12 in)

• Bar and Forgings ≤ 100 mm (≤ 3.94 in)

• Wire ≤ 12 mm (≤ 0.47 in)

ISO V-Notch Impact Toughness

For plate material up to 50 mm (1.97 in) thick, in the solution-annealed condition at 20°C (68°F) with a grain size ≥ 70 μm, as per TÜV Material Data Sheet 540:

Transverse: > 56 J/cm2

Longitudinal: > 69 J/cm2

Creep Resistance

Based on TÜV Material Data Sheet 540, the solution annealing temperature of this alloy is 1220°C (2228°F) with a grain size ≥ 70 μm. Using the Rp1.0 creep limit (minimum transformation temperature) as a basis and a safety factor of S=1.5, the long-term creep strength design value is suitable for temperatures above approximately 625°C (1157°F). For lower temperatures, even higher creep strength values can be expected.

Corrosion Resistance

This alloy has excellent oxidation resistance, even better than Alloy 601, with a maximum application temperature of 1200°C (2192°F). Due to its tightly adherent, non-spalling aluminum oxide layer, the alloy maintains this performance even under cyclic heating and cooling conditions.

High-temperature oxidation tests also show the lowest mass loss of this alloy compared to other high-temperature materials under cyclic stress conditions. The chromium and aluminum content provide excellent corrosion resistance in high-temperature oxidizing sulfur-containing atmospheres. Alloy 602 CA further enhances the good carburization and metal dusting resistance of Alloy 601.

Material Applications

This alloy is widely used in high-temperature applications in the power generation, chemical, and automotive industries, such as:

• Radiant tubes

• Furnace insulation shields

• Rotary and shaft-type furnaces

• Kiln rollers and other furnace equipment

• Glass containers for melting radioactive waste

• Methanol and ammonia synthesis

• Hydrogen production

• Reformer reactors in the chemical and petrochemical industries

• Automotive exhaust system components

• Glow plugs for diesel engines

• Coolers for syngas in biofuel production

Fabrication

Alloy 602 CA is readily cold and hot formed and machined. Care must be taken to ensure the workpiece is clean and free of contaminants (e.g., marking paints, indicators, lubricants, fuels) during heat treatment, which can be performed using gas, oil, or electric heating equipment in a ventilated, protective atmosphere, or vacuum environment. Low-sulfur natural gas (< 0.1%) and fuel oil (< 0.5%) are suitable for mild oxidizing furnace atmospheres.

The alloy can be hot formed between 1200°C and 900°C (2192°F and 1652°F), and it is recommended to perform a heat treatment after hot forming to achieve optimal properties. The material should be in the solution-annealed condition prior to cold working. The alloy has a higher work-hardening rate than austenitic stainless steels, which should be considered in the selection and design of forming equipment and processes. Intermediate annealing is required for extensive cold working, and solution annealing is recommended if the deformation exceeds 7%. When bending and shearing plate material, the bend radius should be greater than three times the thickness to avoid material damage.

Heat Treatment

The alloy exhibits the best creep strength in the solution-annealed condition. Solution annealing is performed at 1220°C (2228°F) with a grain size ≥ 70 μm. If further processing is required after solution annealing, rapid cooling using water or compressed air is recommended for material thicknesses ≤ 3 mm.

The alloy is highly susceptible to stress-relief cracking in the temperature range of 600°C to 750°C, and stabilization annealing is required for long-term use in this temperature range. Stabilization annealing should be performed at 950°C (1742°F) for at least three hours, with a slow cooling rate to avoid distortion.

Descaling and Pickling

The protective oxide layer that forms on high-temperature materials during use has better adherence on this alloy compared to stainless steel, and the heat tint around welds is also more adherent. Therefore, it is recommended to use fine-grained abrasive belts or wheels for grinding to avoid damaging the material. If pickling is required, the time and temperature should be carefully controlled to avoid corrosion of the material.

Machining

The alloy is best machined in the solution-annealed condition. Due to the work-hardening tendency of the alloy, lower cutting and feed speeds should be used. The heat generated during machining should be controlled using water-based coolants.

Welding Recommendations

Welding should be performed in a dedicated area, and gas-shielded welding processes should be used to prevent drafts at the welding site. Tools previously used for other materials must not be used for welding nickel alloys and stainless steels. Mechanical methods, such as turning, milling, or planing, should be used to prepare the welding groove. Striking the arc should only be done within the weld area, such as at the groove edges or on a backing bar.

After welding, the material can be cleaned with a wire brush while still hot, without the need for pickling, to remove any heat tint and restore the desired surface condition. If the welded component is to be used in the temperature range of 600°C to 750°C (1112°F to 1382°F), stabilization annealing may be required.

Available Products

Shanghai COCESS Special Alloys Co., Ltd. can supply Inconel 602CA in the form of bars, plates, strips, tubes, and wires. Please contact us for more product details.