Abstract
Research was conducted to develop a criterion for selecting weld overlay coatings for erosion mitigation in circulated fluidized beds (CFBs). Initially, 11 weld overlay alloys were deposited on 1018 steel substrates using the plasma arc welding process and erosion tested at 400°C. Erosion resistance was evaluated by determining the steady state erosion rate, and the microstructure of each coating was characterized before erosion testing. The steady state erosion rates for several weld overlay coatings (Ultimet, Inconel-625 and 316L SS) were considerably lower than the other coatings evaluated (Armacor-M, B-60, TS-2, Stellite-6, Hastelloy-22, high Cr iron and 420 SS). No correlations were found between the room temperature hardness of the weld overlay coatings and their erosion resistance at elevated temperature. Microhardness tests were performed on the eroded samples below the erosion surface in order to determine the size of the plastically deformed zone, and it was found that some coatings deformed plastically as a result of erosion while others did not. Possible erosion mechanisms for these groups of coatings were analyzed.
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