HVOF Sprayed WC Based Cermet Coating for Mitigation of Cavitation, Erosion & Abrasion in Hydro Turbine Blade

Abstract

Considerable advancement has been made over the last decades in various thermal spray technologies, practices and applications. However, like other technologies, they have to continuously evolve to meet new troubles and industrial requirements. WC-based hard metals are widely used in industry mainly are being developed for a wide variety of applications to resist wear, erosion and cavitation due to their high hardness and toughness. Slurry erosion, abrasive wear andcavitation erosion problems are found in turbine runners as well as in other parts of the system. Slurry erosion complications are especially important during rainyPeriods in hydroelectric power plants owing the growth in the number of abrasive particles impacting the exteriors, especially in systems where the comprehensive clarification process is not possible. Portions in interaction with fluids usually needdistinctmaintenanceincluding time consuming heat treatments processing, welding, use of super alloy etc. Thermal spray coatings are appears as a practical alternative to the costly and health hazardous hard chrome plating to repair components and prevent excessive wear because during the deposition process no significant changes to the microstructure of substrates. The term thermal spray describes a family of processes that use chemical or electrical energy to melt (or soften) and accelerate particles of a material which is then deposited on a surface. HVOF sprayed cermet coatings have very low porosity, high hardness, high abrasive resistance, good wear resistance. The review presents the concerns related to materials and the fabrication process of protective wear resistant coatings by thermal spraying methods used for the protection of hydro turbine system.