Cavitation Erosion Testing

What is Cavitation?

Cavitation is a form of erosion caused by the implosion of gas bubbles on a surface resulting in damage and material loss. We use vibratory apparatus to simulate the formation and collapse of cavities in a test liquid. This enables us to study, rank and compare the nature and progression of cavitation damage against other materials.

We have the facilities and expertise to provide cavitation erosion testing in accordance with the ASTMG32 standard.

How we test Cavitation resistance

Testing is carried out according to the ASTM G32 Standard, “Test Method for Cavitation Erosion Using Vibratory Apparatus” in either pure or salt water. To plot cumulative erosion vs exposure, we periodically interrupt the test and measure mass loss for 8 to 12 hours. If the material density is known we can convert to a mean depth of erosion to directly compare materials.

Cavitation erosion testing

3D imaging of wear surface

How we analyse the surface

As well as testing cavitation, we can identify cavitation-related failure mechanisms and evaluate the level of damage present on working equipment such as pumps and impellers. We use materials characterization techniques to analyse the damage.

Sample and Horn

The equipment uses a 20 kHz transducer with 16 mm diameter horn with a peak to peak amplitude of 50 microns. A sample size of 25 x 25 x 5 mm is inserted in to the test tank with deionized water at 25 degrees centigrade and a stand off distance set to 0.5 mm.
Hourly monitoring

The mass loss is monitored at hourly intervals. Images are also captured hourly to reveal the progression of damage as can be seen in aluminium (top) and tungsten carbide (bottom).
Cumulative Erosion

According to ASTM G32, the erosion goes through several stages; incubation, acceleration, maximum rate and deceleration. If the density of the material under test is known, the mean depth of erosion can be calculated and the stages can be estimated.
Cavitation Performance
Optical microscopy

A more in depth study can reveal the stages of cavitation over time using characterization techniques. Often these include optical and scanning electron microscopy along with non contact profilometry.
Materials Characterization
Profilometry

The Alicona infinite microscope can provide 3D images of the damage caused by cavitation as well as a profile of the surface. Pictured is a tungsten carbide sample with the surface profile analysed at 1, 2, 4 and 8 hours.
Materials Characterization
Scanning electron microscopy

SEM images taken at various stages can also reveal the progression of the cavitation damage over time.
Materials Characterization
Scanning electron microscopy

A cross section through the material can also reveal interesting images.
Materials Characterization