Slurry erosion behaviour of HVOF sprayed coatings on hydro turbine steel: A review

Abstract

Abstract Slurry erosion is one of the unavoidable problems in the operation of hydro power stations all over the world. Erosion mainly depends on the surface properties of the hydro turbine material and the different level of operating parameters like impact angle, impact velocity, slurry concentration, particle size and shape. Thermally sprayed hard metal coatings are widely used to protect components and surfaces against erosion wear in various applications. This study focuses on the slurry erosion behaviour of high velocity oxy-fuel (HVOF) sprayed coatings on hydro turbine steel. The HVOF sprayed coatings such as WC-CoCr, Cr3C2-NiCr, Al2O3, stellite, Cr2O3, Cr3C2–NiCr, NiCrSiB–35wt%WC–Co, WC–10Co– 4Cr and WC-12Co results in high bond strength, lower porosity and high resistance to slurry erosion. In this review paper, comprehensive and significant investigation has been made on existing literature of HVOF sprayed coatings on the material of hydro turbine components. The reported research work reveals that the predominant causes of slurry erosion of the uncoated hydro turbine steel include micro-cutting, micropores, cracks, craters, microchipping, pullout, de-bonding and spalling which can be effectively minimize by applying HVOF sprayed coatings.