High-energy particle impact wear resistance of hard coatings and their application in hydroturbines

The problem of erosion due to silt in a number of Indian hydro power stations is found to be quite serious, especially in those located in the Himalayan region. Erosion is a function of different parameters such as silt size, hardness, concentration, quantity, shape, velocity and base material properties. In most cases, this can be minimised by controlling the above-mentioned parameters. During monsoon season, it becomes impossible to control these parameters which cause erosion. So, it is essential to know their effects. Wear, which occurs due to low and high-energy particle impact, can be controlled by velocity or by controlling silt size, shape and concentration. The low energy impact wear can also be controlled by providing suitable hard coatings. However, this becomes critical for high particle impact wear. An experimental study was undertaken for understanding its nature. In this study, hard coatings such as hard chrome plating, plasma nitriding, D-gun spraying and boronising were studied for high-energy impact wear resistance. Boronising appears to be excellent for this, followed by D gun sprayed WC+12Co coating. Based on this experimental study, boronising is being field-tried on a component which is prone to erosion due to high-energy particle impacts.