Cavitation erosion is a current wear type in hydraulic turbines, on
pump impellers, on ship propellers, valves, heat-exchanger tubes and other
hydraulic structures in contact with high-velocity liquids subjected to
pressure changes. Much effort has been done to optimise the design and
operating parameters in order to avoid cavitation wear for the equipment.
But, this type of wear has also been observed in mechanical devices which
such as plain bearings, seals, orifices in which fluid goes through severe
restrictions. Cavitation damage may occur when surfaces in contact with
fluid are subjected to vibrations, e.g.: water-cooled Diesel-engine cylinder
liner. Sometimes, cavitation can initiate other types of wear such as
adhesion or abrasion because of wear particles produced at the friction
interface, making the failure analysis more difficult.
Cavitation wear mechanisms were showed through three industrial examples.
The first one is a hydrodynamic plain bearing which was heavily damaged by
cavitation wear due to flow instability. The second one concerns a low speed
translating plain bearing. Firstly, abrasion traces were observed on the
contact surface. But a deeper study showed that solid particles produced by
cavitation wear had been the main cause of the abrasion wear. The last
example presents several cases of cavitation damage in oil lubricated plain
bearing observed in medium/slow speed diesel engine for marine or power
station applications. Because of fluctuation of radial force from crankshaft
and instability of lubricant flow, variation of oil pressure can be
sufficient to produce bubble inception, collapse and microjet formation
process.