| Introduction to the Ball Cratering
The Ball Cratering Tester is widely used for analyzing coatings with thickness typically between 0.1 to 50 microns. The motorized shaft on which the ball rotates is held by an adjustable arm which allows greater flexibility in how the ball is positioned on a sample. For samples which are too big to be mounted in the sample holder the complete arm and motor assembly can be removed and directly clamped to the side of the sample using the magnetic foot provided. This test provides quick, simple and inexpensive determination of coating thickness. A rotating sphere with a know diameter (Ø ball) is pressed on the coating surface with a pre-selected load. Both the position of the sphere relative to the sample and the contact load are constant.Upon adding abrasive paste to the contact zone, a depression with the shape of a spherical cap is abraded into both the coating and the substrate. Optical inspection of the depression reveals the projected surfaces of the abraded coating and substrate sections. By measuring the parameters X and Y, the thickness of the coating D can be calculated by a simple geometrical equation. By comparing the geometry of the crater for different periods of wear time, the wear rate of coatings and substrates can be evaluated. |
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