Effect of Iron-Aluminide Coating on the Fracture Mechanism of Ferritic-Martensitic Steel in Coal-Fired Boilers Environment

摘要

Due to the coal combustion that generates halides, steel components can confront hot corrosion during applications at high temperature. The hot-dipping aluminum (HDA) was operated on the 9Cr-Mo steel (grade 91) to form the iron aluminide layer. A hot corrosion-loading test of aluminized grade 91 (HDA-91) was carried out by covering a salt mixture of NaCl/Na2SO4 under static load ranging from 75 to 100 MPa at 600 degrees C and 700 degrees C, respectively. The failure mechanism was assessed after various elongations using scanning electron microscopy and optical microscopy. The results showed that HDA-91 presented higher hot corrosion resistance than the uncoated grade 91. The aluminide layer formed a higher ductility oxide and prevented the substrate form grain-boundary oxidation at high temperatures, resulting in durability. The results also revealed a significant improvement in reduction of area during the hot corrosion-loading test for grade 91 that underwent HDA treatment.