A new alloy with high chromium has shown excellent resistance to corrosion in combustion atmospheres like those produced in low NOx coal-fired power boilers. This new material is Alloy 33 (UNS R20033) and contains approximately 33% chromium. Chromium is well known as a key alloy addition to improve resistance to sulfidation, which is the major corrosion mechanism in coal-fired boilers using low NOx combustion technologies. In addition, the alloy 33 shows less segregation of alloying elements than currently used materials when in the welded condition; segregation in welds has been suggested as playing a contributing role in boiler tube corrosion and corrosion assisted cracking mechanisms. The improved corrosion resistance of Alloy 33 demonstrated in this study is expected to result in longer life of the weld overlay used to protect boiler tubes. Because of the complex nature of boiler environments, a field test is now being perused to demonstrate the benefit of alloy 33 under actual service conditions.

Subject
Materials, Corrosion resistant alloys, Corrosion rate, Materials performance, Tubes, Molybdenum alloys, Atmosphere, Weight change, Corrosion scales, Sulfidizing, Boilers, Corrosion resistance, Alloys
Keywords:
Alloy 33, Alloy 622, Alloy 50, low NOx, boiler, weld, weld overlay, sulfidation
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2004
Association for Materials Protection and Performance (AMPP)
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