Wet-Sand Rubber-Wheel Abrasion Test for Thin Coatings

One category of machines for determining the low-stress abrasion resistance of materials uses a rubber wheel rotating in a water-sand slurry and rubbing against a stationary specimen. Using the Wet-Sand Rubber-Wheel Abrasion Test Method being developed by the SAE produces a wear scar on the order of 0.25 mm deep in normalized 1090 steel at HRC 30, and so may be unsuitable for testing thin coatings and surface treated materials. This was confirmed in testing boride coatings on steel, the coatings being penetrated prior to completion of the test.

Modified practices were investigated in order to determine procedures more suitable for wet-sand rubber-wheel testing of coatings. Tests were conducted using the SAE Practice, with three rubber wheels of varying rubber hardness but with reduced numbers of revolutions per wheel, and using single rubber wheels and repeated increments of varying numbers of wheel revolutions. The criterion for acceptance of a modified practice was the correlation of weight loss (wear) ratios obtained for selected materials with those obtained using the SAE Practice. Results are discussed in terms of this correlation, and selected modified practices were evaluated for three highly varied coating types; electroplated chromium, a boride diffusion coating, and plasma-sprayed alumina, all on plain carbon steels.