Cavitation Erosion in Hydraulic Turbine Components and Mitigation by Coatings: Current Status and Future Needs

Cavitation erosion is a frequently observed phenomenon in underwater engineering materials and is the
primary reason for component failure. The damage due to cavitation erosion is not yet fully understood, as
it is influenced by several parameters, such as hydrodynamics, component design, environment, and
material chemistry. This article gives an overview of the current state of understanding of cavitation erosion
of materials used in hydroturbines, coatings and coating methodologies for combating cavitation erosion,
and methods to characterize cavitation erosion. No single material property fully characterizes the resistance
to cavitation erosion. The combination of ultimate resilience, hardness, and toughness rather may be
useful to estimate the cavitation erosion resistance of material. Improved hydrodynamic design and
appropriate surface engineering practices reduce damage due to cavitation erosion. The coatings suggested
for combating the cavitation erosion encompasses carbides (WC Cr2C3, Cr3C2, 20CrC-80WC), cermets of
different compositions (e.g., 56W2C/Ni/Cr, 41WC/Ni/Cr/Co), intermetallic composites, intermetallic matrix
composites with TiC reinforcement, composite nitrides such as TiAlN and elastomers. A few of them have
also been used commercially. Thermal spraying, arc plasma spraying, and high velocity oxy-fuel (HVOF)
processes have been used commercially to apply the coatings. Boronizing, laser surface hardening and
cladding, chemical vapor deposition, physical vapor deposition, and plasma nitriding have been tried for
surface treatments at laboratory levels and have shown promise to be used on actual components.