Standard Test Method for Erosion of Solid Materials by Cavitating Liquid Jet

Importancia y uso:

5.1 This test method may be used to estimate the relative resistances of materials to cavitation erosion, as may be encountered for instance in pumps, hydraulic turbines, valves, hydraulic dynamometers and couplings, bearings, diesel engine cylinder liners, ship propellers, hydrofoils, internal flow passages, and various components of fluid power systems or fuel systems of diesel engines. It can also be used to compare erosion produced by different liquids under the conditions simulated by the test. Its general applications are similar to those of Test Method G32.

5.2 In this test method cavitation is generated in a flowing system. Both the velocity of flow which causes the formation of cavities and the chamber pressure in which they collapse can be changed easily and independently, so it is possible to study the effects of various parameters separately. Cavitation conditions can be controlled easily and precisely. Furthermore, if tests are performed at constant cavitation number (σ), it is possible, by suitably altering the pressures, to accelerate or slow down the testing process (see 11.2 and Fig. A2.2).

5.3 This test method with standard conditions should not be used to rank materials for applications where electrochemical corrosion or solid particle impingement plays a major role. However, it could be adapted to evaluate erosion-corrosion effects if the appropriate liquid and cavitation number, for the service conditions of interest, are used (see 11.1).

5.4 For metallic materials, this test method could also be used as a screening test for applications subjected to high-speed liquid drop impingement, if the use of Practice G73 is not feasible. However, this is not recommended for elastomeric coatings, composites, or other nonmetallic aerospace materials.

5.5 The mechanisms of cavitation erosion and liquid impingement erosion are not fully understood and may vary, depending on the detailed nature, scale, and intensity of the liquid/solid interactions. Erosion resistance may, therefore, arise from a mix of properties rather than a single property, and has not yet been successfully correlated with other independently measurable material properties. For this reason, the consistency of results between different test methods (for example, vibratory, rotating disk, or cavitating jet) or under different experimental conditions is not very good. Small differences between two materials are probably not significant, and their relative ranking could well be reversed in another test.

5.6 Because of the nonlinear nature of the erosion-time curve in cavitation erosion, the shape of that curve must be considered in making comparisons and drawing conclusions. Simply comparing the cumulative mass loss at the same cumulative test time for all materials will not give a reliable comparison.

Subcomité:

G02.10

Referida por:

G0032-16R21E01, G0073-10R21

Volúmen:

03.02

Número ICS:

19.060 (Mechanical testing)

Palabras clave:

cavitating jet; cavitation; cavitation erosion; erosion by liquids; erosion of solids; erosion test; flow cavitation;