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    Effect of the cooling in the austempering process on the abrasive wear behavior of austempered ductile iron
    (2006) Çetin, M.; Gül, F.
    In this study, ductile iron was austenised at 900°C for 1 h and austempered at 400°C for 2 h in single step austempering process, whereas it was austenised at 900°C for 1 h and immediately quenched in a salt bath at 400°C for 10 minutes and then the temperature of bath was decreased by 1.88°C per minutes down to 250°C in two-step austempering process. The upper ausferritic austempered ductile iron (ADI) specimens produced by conventional single step austempering process and the upper and lower ausferritic specimens produced by two-step austempering process were abraded on the pin on disc apparatus under the normal load of 10, 20, 30 N, by rubbing the specimens on abrasive Al 2O 3 grains with diameters of 180 Mesh (80 ?m). Although the ductile iron austempered in two steps had higher hardness than the ductile iron austempered in single step, they showed similar abrasive wear behavior. In addition, the abrasive wear resistance of two step austempered specimen increased with increasing applied load.
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    Effect of the matrix structure on the friction coefficient and pin tempureture of ductile iron under dry sliding conditions
    (2007) Çetin, M.; Gül, F.
    In this study, the effect of the matrix structure on the dry sliding wear behaviour, friction coefficient and pin temperature of ductile irons was investigated. Wear tests were carried out at normal atmospheric conditions and room temperature on a pin on disc type tester at constant sliding speed (1ms-1) and sliding distance (3.6 km) under various sliding loads in a range of 20 to 60 N. The worn surfaces were examined by scanning electron microscopy (SEM). Wear rate of as-cast ferritic ductile irons increased with increasing test load, whilst that of as-cast pearlitic irons decreased. Tests revealed that, as-cast pearlitic ductile iron exhibited higher friction coefficient and friction temperature than as-cast ferritic ductile iron. The experimental results showed that the friction temperature increased with decreasing the friction coefficient of as-cast ferritic and pearlitic ductile irons.