Test Methods

The selection of a "most suitable" wear test method is very often difficult. An important consideration is "will the laboratory test results correlate with real life results?" Other considerations for selection of the appropriate test include cost, amount of time for a test, availability of test equipment, and availability of trained personnel to prepare the test specimens, perform the tests carefully, and properly interpret the results.

There are a number of types of wear that are of concern to the user of coatings. We will describe several popular wear tests for evaluating the following types of wear: sliding wear and friction, low-and high-stress abrasion, gouging abrasion, dry particle erosion, and slurry erosion.

Sliding Wear and Friction • Crossed Cylinder Test

The crossed cylinder test was developed to evaluate the resistance of metallic materials to metal-to-metal contact and adhesion. An ASTM standard (1), designated ASTM G83-83, was adopted for testing similar and dissimilar metals and alloys in unlubricated conditions. The method lends itself well to the study of sliding wear in metallic and nonmetallic coatings. A rotating cylinder is forced at right angle against a stationary cylinder with a force of 16 pounds while rotating at speeds 10,000, 40,000, or 80,000 revolutions, depending upon the standardized procedure used. A schematic of the test is shown in Figure 1. The volume of material loss corresponding to wear loss on each cylindrical specimen is calculated by means of the equations:

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