Coatings for Hydro Turbine Applications: A Materials Perspective

Corrosion- and wear-resistant coatings are widely applied to hydro-turbine runners through thermal spray and cladding processes to enhance component efficiency and structural integrity by mitigating material loss during operation. This work provides a critical review of both mature and emerging coating materials, with particular emphasis on cermets, Fe-based amorphous alloys, high-entropy alloys, and functionally graded coatings. Their performance is analyzed in terms of wear, corrosion resistance, and applicability under hydro-turbine service conditions, highlighting the advantages and current limitations that hinder broader industrial adoption. The review identifies key challenges associated with materials chemistry, deposition processes, coating architecture, and cost-effectiveness, emphasizing the need for further advancements to improve coating reliability and competitiveness. In addition, a shift in coating design philosophy is proposed, moving toward a performance-driven and application-oriented approach in which coating properties are tailored to meet specific service demands through optimized material selection and process control. By integrating current knowledge and identifying critical gaps in the literature, this work provides a framework to guide future research efforts aimed at developing next-generation coatings for hydro-turbine applications.