Diseño y construcción de un sistema calotest para evaluar la resistencia al desgaste de superficies duras: diseño mecánico.

Abstract

To equip the material’s laboratory with an instrument that can characterize the thickness of hard coatings and evaluate their resistance to wear, the device called "Calotest" was built. The operation of this equipment consists of rotating a steel sphere over a sample at high revolutions, a relative friction is generated between the parts due to the roughness of the materials, and as there is a single point of contact between both surfaces, a micro abrasion is produced, which has a shape of two concentric circles for flat samples and concentric ovals for cylindrical or spherical samples. By means of a geometric analysis it is deduced that there is a direct relationship between the thickness of the coating and the distances of these concentric circles or ovals. The first distance is the one measured from one point of the external diameter of the surface crater to the other end of the internal crater of the base material, the second measurement is the width between the two circles, The diameter of the sphere is multiplied by these two values, and their division yields the thickness of the substrate layer., in addition, the with the internal diameter in the substrate and the sliding distance that made the sphere in the sample can be calculated to the roughing volume. The performance of the equipment was tested with two chrome-plated steel shafts and its thickness was validated using ultrasound equipment, finding that the measurement error is less than 25%.