Caracterización de la dureza del acero Chronit 400 sometido a fricción rotacional a 70rpm y 700 rpm con una carga aplicada de 5 kg en intervalos de tiempos de 1 a 6 horas

Abstract

This research focused on characterizing the hardness and friction resistance of Chronit 400 steel, aiming to predict its performance and service life under prolonged service conditions, especially in harsh environments with abrasive substances that accelerate wear. To this end, the friction resistance of steel specimens was evaluated by applying controlled stresses. The experimentation consisted of subjecting circular specimens with a central groove to friction tests against hardened spheres. The rotation of the specimens in a lathe, at speeds of 70 and 700 rpm, generated friction under a constant force of 5 kgf for consecutive periods of 1 to 6 hours. Subsequently, the hardness of the specimens was measured to analyze the effects of wear and characterize their resistance to plastic deformation. The results revealed a significant increase in material hardness after machining, with hardness increasing from 42.9 HRC (as-supplied condition) to 56.7 HRC (a 32.17% increase). Friction hardening was even more pronounced at 700 rpm, reaching a maximum hardness of 66.6 HRC, compared to 59.56 HRC obtained at 70 rpm (an 11.82% difference between the two studies). It was also observed that most of the work hardening occurred within the first 3 hours of friction, subsequently stabilizing at both rotation speeds. However, the speed directly influenced the maximum hardness value achieved, as a higher rotation speed resulted in a higher plastic deformation rate, confirming this as the main hardening mechanism. Similarly, the test curves allowed for the development of numerical approximations using 4th-degree polynomials, with high correlation coefficients (R² of 0.99 and 0.98 for each experiment, respectively), enabling the inference of behavior at higher speeds and the prediction of hardness during service life. It was found that Chronit 400 steel tends to harden by deformation, especially in the surface layers (58 HRC to 66 HRC), exceeding the hardness of the inner layers and, therefore, increasing its wear resistance. It is worth noting that no excessive material detachment was observed during friction at low speeds.