Effect of Y2O3 addition on the microstructure and liquid LBE cavitation erosion behaviors of Fe-Cr-Al-Ti-C-xY2O3 laser clade coatings

Abstract

Fe-Cr-Al containing alloys with high resistance to lead-bismuth eutectic (LBE) is considered as one of the candidate materials for the protective coating. But it remains challenge in improving the mechanical properties and resistance to cavitation erosion under the environment of flowing LBE. In this study, Fe-Cr-Al-Ti-C coatings were synthesized with different Y2O3 additions by laser cladding, aiming at improving toughness and cavitation erosion resistance. The results showed that the Fe-Cr-Al-Ti-C coating mainly contained Fe2AlCr and TiC phases, and the addition of Y2O3 led to the formation of Y2TiO5 and Y2Ti2O7, modifying the distribution of TiC. Y2Ti2O7 and Y2TiO5 played a toughening role by purifying impurity oxygen at the grain boundary (GB), and various secondary phases are coordinated. When the addition of Y2O3 is 0.2 wt.%, the cladding coating was well formed, and showing the highest hardness and adhesive strength, which directly affected the resistance to LBE cavitation erosion. When the addition of Y2O3 was more than or equal to 0.8 wt.%, severe segregation of TiC appeared at the GBs, resulting in the decrease of mechanical properties. At 500°C LBE cavitation erosion test, the main damage mechanism of the coating was lamellar spalling. Cracks would initial at the surface under the impact of cavitation erosion and expand into the materials. The addition of Y2O3 reduced the size of crack and improved the LBE cavitation erosion resistance of the cladding coating.