RA 602 CA® (UNS N06025)
RA 602 CA® alloy is the most oxidation resistant/high strength nickel alloy available. It is capable of extreme temperature use up to 2250°F (1232°C). For thermal processing applications where minimal product contamination is necessary, the oxidation/scaling resistance of RA 602 CA is extremely desirable. A high chromium content, along with aluminum and yttrium additions, allows the alloy to develop a tightly adhering oxide scale.
A relatively high carbon content combined with the alloying additions of titanium and zirconium results in high creep rupture strength. RA 602 CA provides 150% of the strength of other commonly used nickel alloys such as alloy 600.
ASME Code Case 2359, ASME SB 166, ASME SB 168
ASTM B 166, ASTM B 168
W. Nr./EN 2.4633
RA 602 CA® Plate, RA 602 CA® Round Bar, RA 602 CA® Sheet, RA 602 CA® Welding Products
Common Trade Names
- Outstanding resistance to cyclic oxidation through 2250°F (1232°C)
- Excellent high temperature creep strength
- Resistant to carburizing and nitriding environments
- Highly resistant to grain growth in service
- Superior behavior in oxidizing/chloridizing environments
- Good resistance to metal dusting
Extended exposure to methane (CH4), carbon monoxide (CO), and other carbon rich gases can lead to carburization. As heat resistant alloys absorb carbon, their ductility will gradually decrease. Alloys that are high in nickel, such as RA 602 CA possess excellent resistance to carburization attack.
Metal dusting is a form of carburization that can lead to the rapid corrosion of heat resistant alloys. The combination of high aluminum and chromium additions to RA 602 CA results in a resistance to metal dusting superior to alloys such as RA330, alloy 600, alloy 601, and 800H/AT alloy.
It is suggested to weld RA 602 CA with RA 602 CA weld consumables. These are available from Rolled Alloys in spooled wire (GMAW, MIG), bare wire (GTAW, TIG), and coated electrodes (SMAW).
For joints less than 3/16 inch thick, 100% argon is acceptable for a shielding gas. For heavier joints it is recommended to use AR Ni5He5CD300 gas from AirGas which was designed to reduce the likelihood of weld solidification cracks. For GTAW welding the use of 98% Argon, 2% Nitrogen for the shielding gas is suggested to minimize the likelihood of weld solidification cracking. More detailed information on welding is available in the RA 602 CA data sheet.
RA 602 CA has a high carbon content, and work hardens rapidly. RA 602 CA may be bent 120° around a diameter equal to three times the material thickness (3T bend) for material up to 0.4” (10 mm) thick. This grade cannot be bent to as tight a radius as the lower carbon alloys, e.g, RA600 or RA330. As with other nickel alloys, the shear drag (burr) should be removed, or placed on the inside of the bend. During bending this heavily cold-worked burr may initiate cracking. Sawed plate may be preferred for severe forming operations.
RA 602 CA may be hot-worked in the temperature range 1200 to 900°C (2190 to 1650°F), followed by water quenching or rapid air cool. As with other austenitic alloys, do not attempt to form in the 600-800°C (1100-1500°F) temperature range. Do not heat RA 602 CA, or any other nickel alloy, with a torch to bend it. The lack of temperature control will often result in cracking.
RA 602 CA is one of the most oxidation resistant nickel alloys available. Chromium (25%) supplemented with aluminum (2.2%) and a micro-alloying addition (0.1%) yttrium form a very thin protective oxide scale. The aluminum addition allows for the formation of a continuous homogenous self repairing AI2O3 subscale. The addition of yttrium improves the adhesion and spalling resistance of the chromium and aluminum oxide scales. The extremely low scaling rate of RA 602 CA makes it an excellent candidate for applications such as high purity alumina calciners, where minimal contamination from scaling is permissible.