Cavitation erosion is a severe form of surface damage that affects pumps, valves, turbines and other fluid-handling equipment. Unlike abrasion, it is not caused by solid particles, but by the liquid itself.
Over time, cavitation erosion can reduce efficiency, increase vibration and noise and significantly shorten component life. This makes it a key integrity challenge in high-pressure hydraulic systems.
When a liquid flows through a system at high velocity or through areas where the pressure drops sharply, the local pressure can fall below the liquid’s vapour pressure. At this point, the liquid begins to vaporise and form tiny bubbles, a process called cavitation. These bubbles are carried into regions of higher pressure downstream, where they collapse or implode suddenly.
This implosion generates extremely high local pressures and shock waves in the fluid, which can exert significant mechanical stress on nearby solid surfaces. In many engineering environments, this process repeats many thousands of times per second, creating severe load cycles on component surfaces.
At the center of cavitation erosion is the collapse of vapour cavities right beside a solid boundary. These collapses produce microjets and shockwaves that impact the surface at very high speeds and pressures. Over time, these repetitive, high-energy impacts cause surface fatigue, pitting and, eventually, the loss of material from the surface.
The process has similarities with impact fatigue but is uniquely driven by fluid dynamics instead of repeated solid contact. It typically begins with microscopic pits that grow as cavitation continues, increasing surface roughness and making the component more susceptible to further damage.
Cavitation erosion is especially prevalent in high-speed fluid environments. Common locations include:
Even in the absence of solid particulate matter, cavitation erosion can rapidly degrade component surfaces and significantly shorten service life. This damage leads to reduced efficiency, increased vibration and noise, more frequent maintenance, and in severe cases, catastrophic failure of the component or system.
The extent and severity of cavitation erosion depend on several interacting factors:
No material is completely immune to cavitation erosion, and the interplay between mechanical properties and flow dynamics makes prediction and mitigation challenging.
In practical applications, cavitation erosion can manifest as pitting, loss of surface material, distortion of hydraulic profiles, and changes to flow characteristics. For instance, a pump impeller suffering from cavitation erosion may exhibit reduced flow efficiency, increased energy consumption and a noisy “marbles in the casing” sound that signals the onset of damaging cavitation conditions.
Operators often address these issues through system design changes (such as improved suction conditions, pressure management or flow redistribution) and by selecting materials or surface treatments that better resist the energetic impacts of collapsing vapour bubbles.
Because cavitation erosion is driven by extremely high-energy, repetitive microimpacts at the fluid/solid interface, the resistance of a component against this form of damage is strongly influenced by the surface structure and mechanical resilience of its material. Surfaces with high toughness, minimal porosity and strong mechanical cohesion tend to resist pit initiation and propagation more effectively.
Advanced chemical vapour deposition (CVD) coatings with pore-free, tough microstructures have shown promise in improving cavitation erosion resistance by combining surface hardness with structural integrity. Hardide’s CVD coatings are engineered to deliver that combination of properties, offering enhanced protection for fluid-handling components exposed to aggressive cavitation conditions.
To find out more about the importance of advance coatings to maximise component lifespan, download our guide below.