Performance investigation of high velocity flame sprayed multi-dimensional Ni-TiO2 and Ni-TiO2-Al2O3 coated hydro turbine steel under slurry erosion

Abstract Slurry erosion is one of the primary reasons for performance decrement of hydropower turbines; Therefore, the present study investigates the slurry erosion performance of high velocity flame sprayed (HVFS) nickel matrix base coating compositions in which multi-dimensional sized (submicron, and nanostructured) TiO2, and Al2O3 ceramic particles were added as reinforcement. The experiments were carried out using a non-recirculating jet type slurry erosion test rig. The potential effect of influential parameters such as impact velocity, slurry concentration, and average particle size were also estimated under different erosive conditions. The results showed that the as-sprayed Ni-40TiO2 coating exhibited the highest slurry erosion resistance than Ni-20TiO2-20Al2O3 coating and uncoated steel specimens. Further, the eroded surface of uncoated steel and Ni-40TiO2 coating showed mixed behaviour (ductile and brittle) and Ni-20TiO2-20Al2O3 coating exhibited brittle behaviour as the mechanism of material removal.