Effect of CeO2 on the TiB2 + TiC evolution and water droplet erosion resistance of laser-clad Ni60A coatings

Abstract

In this study, CeO2-doped Ni60A coating was fabricated on the surface of Ti6Al4V alloys. During the fabrication, heterogeneous nucleation occurred between TiB2 and TiC phases within Ni60A coatings, and the TiB2  +  TiC eutectic structure was thereby generated. Ce2O3 phases were formed in-situ by the decomposition of CeO2 powder in the molten pool. On the grain boundary of the CeO2-doped Ni60A coating, Ce2O3 particles were distributed, which inhibited the growth of hard phases TiC and TiB2. Compared with the coating without adding CeO2 powder, the CeO2-doped Ni60A coating had significantly lower crack sensitivity, and the TiB2 phase in the CeO2/Ni60A coating had a far smaller grain size due to the grain refinement effect. In addition, the TiC  +  TiB2 eutectic structure acted as the skeleton in the coating, enabling the coating to effectively resist the shear effect caused by high-speed water particles. After coating Ni60A and CeO2/Ni60A on the Ti6Al4V alloy, the water droplet erosion depth of the alloy was reduced by 38.7% and 53.2%, respectively. Therefore, adding CeO2 powder into Ni60A coatings has great application value in improving the water droplet erosion resistance of steam turbine blades.