Performance of different coating materials against slurry erosion failure in hydrodynamic turbines: A review

The socio-economic development of any country is completely dependent on the energy and the demand for energy is not completely fulfilled from a single source. As a result, renewable sources of energy like solar, wind, and hydro come into the picture. Countries like India and Nepal are naturally gifted with the potential of hydrodynamic energy, where a large number of small and medium hydro-power plants have been installed on the rivers coming from the Himalayas. Most of the hydrodynamic plants are situated in the Himalayan belt and have to deal with the problem of silt erosion in the hydrodynamic machinery. The hydraulic turbine is the heart of any hydropower plant and once it gets damaged due to silt erosion, not only the efficiency of the plant gets affected but it also increases the associated maintenance cost. Over the last two decades, researchers have been continuously working on this problem and focusing extensively to minimize the erosion rates with different materials processed by using surface modification techniques. To prevent the degradation of materials, protective coatings are used, which act as a barrier between the material and the working environment. The current manuscript reviews the performance of modified surfaces, which have been developed by using various surface engineering techniques to combat the slurry erosion failure in hydrodynamic turbines. The deposition of the coating by using different techniques and the evaluation of enhancement in the coating characteristics (mechanical and micro-structural) as well as coating efficiency under different slurry erosion conditions are reported. The effects of different operating parameters such as the angle of impingement, erodent size and shape, and slurry concentration on the performance of coating materials have been studied and discussed in detail.