Alloy 602CA (UNS N06025) is a wrought nickel alloy with a combination of excellent corrosion
resistance and high strength. These attributes make it ideal for use in high temperature
processing of minerals. One particular application where this alloy is widely used is in
fabricating calciner shells. The UNS N06025 has been used in calciners at continuous operating
temperatures up to 1200°C (2192°F) in the processing of a variety of process streams. Corrosion
resistance is achieved by alloying with high chromium levels (25% Cr) in combination with
significant aluminum levels (2.2% Al); rare earth elements (Y and Zr) are also added to maintain
adherence of the protective scale. This not only allows long life for the equipment, but also the
minerals being processed are not contaminated by scale from alloy, which for example is
particularly important when processing high purity alumina used for catalyst substrates. The
high strength is achieved through a unique strengthening mechanism which uses a fine
dispersion of primary carbides to achieve essentially a composite structure. The corrosion
resistance of UNS N06025 is compared to other alloys in a variety of high temperature
environments and several application examples are also given as a demonstration of the benefits
provided by the features of this alloy.
KEYWORDS: Alloy 602CA, Oxidation, Carburization, Strength, Castings, Calciner