The wear resistance of three different types of gray cast iron (gray iron grade 250, high-carbon gray iron and titanium alloyed gray iron), used in brake disc rotors, was studied and compared with the results obtained with a compact graphite iron (CGI). The wear tests were carried out in a pin-on-disc wear-testing machine, the pin being manufactured from friction material usually used in light truck brake pads. The rotating discs (500 rpm) were subjected to cyclical pressures of 0.7, 2 and 4 MPa and forced cooled.The wear was measured by weighing discs and pads before and after the test. The operating temperatures and friction forces were also monitored during each test.The results showed that compact graphite iron reached higher maximum temperatures and friction forces as well as greater mass losses than the three gray irons at any pressure applied. However, when compact graphite iron was tested with lower applied pressures and same friction forces sustained by the gray iron rotors, CGI presented the same performance, as did the gray cast iron.

CGI -Compacted Graphite

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It is discussed the use of ADI (Austempered Ductile Iron) for gears. The gears were produced from continuous cast iron bars, heat treated for grade 3 of ASTM ADI Standard A897M-06 (UTS >1200 MPa), and compared to carburized steel AISI 8620 and to induction hardened steel AISI 4140. Tests on gears were made using equipment developed at UTFPR, measuring the time for pitting and spalling on the surface of the gears. The results show very good potential of using ADI for gears, replacing induction hardened steels. The results show too that the nodule size affects the life of gears, independently of the mechanical properties of the matrix. The ADI with smallest nodules show higher life for pitting formation. It is discussed additionally the mechanisms of crack propagation under the surface of the gears, for all tested materials.