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The current investigation compares the friction behavior between specimens extracted from engine blocks of grey cast iron (class FC 250 ABNT NBR 6589 standard) and compacted graphite iron (class GJV450 ISO 16112 standard). The effect of wall thickness was evaluated, by extracting samples from regions equivalent to two levels of thickness. The piston ring used was a nitrided martensitic stainless steel with an asymmetric profile, and the lubricant oil was the SAE 30 CF. The tribological tests were conducted at 75 N normal load for a duration of 1 hour, a frequency of 5 Hz and a stroke of 10 mm. The tests were carried out at a controlled temperature of 40° C. In a general way, the compacted graphite irons presented smaller friction coefficients when compared to that observed for the lamellar ones; and the wall thickness showed relevance only for the compacted graphite iron, being the lowest values found for the thinner wall.

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.