Treatment and Performance Evaluation of Plasma Nitrided Brake Disks for Baja Prototype

This work aims to demonstrate how to increase the surface hardness, wear resistance and provide a longer service life to a brake disk made of drawn AISI 1045 steel, submitted to plasma nitriding, using a gas mixture of 20% hydrogen (H2) and 80% nitrogen (N2). The influence of treatment time and temperature in four different nitriding conditions were evaluated. Condition I lasted 3 h and at a temperature of $450~^{\circ }$ C; Condition II lasted 4 h at $450~^{\circ }$ C; Condition III lasted 4 h at $500~^{\circ }$ C and condition IV lasted 4 h at $400~^{\circ }$ C. Treatments I-III were carried out at a pressure of 0.8 mbar with a direct current source. For comparative effect due to the complex geometry of the brake disks, an alternative treatment was performed at a pressure of 2 mbar using a pulsed current source with duration of 4 h at $400~^{\circ }$ C. The properties of the nitrided layers obtained in the samples were evaluated by means of surface microhardness profile, X-ray diffractometry, scanning electron microscopy (SEM), and wear test carried out in situ in an off-road prototype of the baja type from Federal Rural University of the Semiarid Region (UFERSA). The results showed an effective improvement in performance, with a significant reduction in disk wear, notably in Conditions III and IV, directly related to the thickness and uniformity of the nitrided layers, as well as to the significant increase in microhardnesses in relation to the standard material, validating the plasma treatment of brake disks as a technological alternative.