Re-sintering Influence on Tribological and Structural Characteristics of Iron-Based Composites for Automotive Applications

Iron-based sintered composites can be used for manufacturing different friction applications for the automotive industry (i.e. brake pads). The present research is a study concerning the influence of the re-sintering on the tribological and structural characteristics of three iron-based friction materials with application in vehicle brake systems. These composites were elaborated by powder metallurgy methods. The chemical composition of the materials contained iron, copper, graphite, nickel, titanium dioxide and/or barium carbonate. First, the three mixtures were homogenized. Green compacts were formed at a compaction pressure of 600 MPa. The sintering was done at 1050 °C, in vacuum for 30 min. The obtained samples were further re-sintered in vacuum, at 1050 °C for 20 min to improve their tribological characteristics. The elaborated materials were characterized by the tribological and structural point of view. The re-sintered samples presented, in general, a higher porosity than the sintered samples. An increase in the friction coefficient was marked out for all three re-sintered materials. Instead, a continuous increase or decrease in the wear rate was not observed. The material that contains titanium dioxide presented the best tribological properties in both sintered and re-sintered states.