Cyclic Oxidation Resistance of MoSi2 Added FeCrAlTiY Coatings on ST41 Steel at 700oC Prepared by a Flame Spraying Technique

Abstract

Advanced power generation will be operated at higher temperatures and pressure to achieve higher efficiency and reduce CO2 emission. This may significantly impact the use of carbon steel that previously has been used in boiler fabrication. In this study, a flame spraying technique was applied to develop a highly resistant coating of MoSi2 added FeCrAlTiY on ST41 steel to improve its oxidation resistance. Four variations of MoSi2 concentration as 0, 10, 20 and 30 in mass% were prepared to investigate the effect of its addition on the cyclic oxidation resistance of FeCrAlTiY coating at 700oC for 8 cycles. The phase composition and microstructure of the coating before and after the oxidation test were analyzed using XRD and SEM, respectively. While the element distribution along the coating was characterized using an EDX. According to the results, partially and fully melted particles, oxides and pores are present in the coatings. It becomes more porous with the increase of MoSi2 concentration. The oxidation test results indicate that the FeCrAlTiY with 10 mass% MoSi2 addition exhibits the lowest mass gain (0.217 mg/mm2) compared to that of MoSi2-free coating (0.261 mg/mm2) and FeCrAlTiY coating with 20 and 30 mass% MoSi2 (0.297 and 0.308 mg/mm2, respectively). As the MoSi2 concentration increases, its addition leads to the deterioration of FeCrAlTiY coating oxidation resistance. The results suggest that FeCrAlTiY-10 mass% MoSi2 is the most resistant coating to cyclic oxidation at 700oC in air and can be applied as a protective coating in advanced power generation.

Keywords

• carbon steel
• fecraltiy
• flame spraying
• mosi2
• oxidation