Coeficiente de atrito estático do par aço AISI H13 temperado e revenido e recobrimento de cromo duro: ensaios em plano inclinado

Abstract

In this work was studied the influence of roughness parameters and mechanical properties of the steel AISI H13 in the coefficient of static friction tested in the inclined plane method. The counterbody used was a coating of hard chrome, considered ideally smooth. The coefficient of friction was related to the real area of contact, taking as input bi-dimensional roughness parameters. The routine calculation proposed by McCool (1987) was applied to obtain an estimate of contact area, using the parameters Rq (root mean square roughness) and Rdq (mean square slope). Three sets of samples were studied, with surface finish produced by grinding flat and different hardness, produced by heat treatments to the samples. The variation of hardness was obtained by different double tempering temperatures: 540, 600 and 640 ° C. The inclined plane tests were conducted at a speed of 0.33 °/s and an applied load produced by the self weight of the body. A motion sensor is attached to the equipment to detect the onset of slip and allow the measure of angle instantly. To analyze the results, each set of samples was considered different depending on the heat treatment. In addition, subsets of samples were distinguished in accordance with Rq parameter, because it is an average parameter and it is used directly to calculate the real area of contact. Thus, for each metallurgical condition was possible to see, the variation of the coefficient of static friction with mechanical and surface properties. It was verified that the hardness had no effect on the coefficient of static friction, however, the combination of mechanical and surface properties represented by the plasticity index has a direct relationship.