This paper deals with the effects of the addition of 0.00031, 0.00064, 0.001 and 0.0042 wt.% Bi on the matrix structure of ductile iron castings consisting of 7 sections of different thicknesses (3, 12, 25, 38, 50, 75 and 100 mm) and contain low content of Si (2.11 wt.%) and pearlite promoting element (0.018 wt.% Cu, 0.0055 wt.% Sn, 0.00041 wt.% Sb, 0.098 wt.% Mn). The Bi contents of 0.00031, 0.00064 and 0.001 wt.% were not significantly affected the share of ferrite and pearlite in the section thicknesses of 12, 25, 38, 50, 75 and 100 mm compared to the casting which does not contain Bi. In all these sections the share of pearlite was increased and the share of ferrite was decreased by the addition of 0.0042 wt.% Bi. All of the above-mentioned Bi contents were resulted in the formation of iron carbides in the section thickness of 3 mm. The share of carbides increases with increasing Bi content.
Keyword: matrix structure
In this study, the effects of matrix structure (pearlitic, tempered martensitic, lower ausferritic, and upper ausferritic), boronizing temperature (800, 825, and 850°C) and time (3, 4.5 and 6 hours) on the wear behaviour of Cu-Ni-Mo alloyed ductile iron were investigated. Wear tests were performed on ball-on-disc type wear tester under the load of 6.8 N, at sliding speed of 6.5 mm/s, at room temperature and dry sliding conditions. The mass losses were measured after wear tests and the friction coefficients were obtained during wear tests. The hardnesses and thicknesses of boride layers, microstructures and worn surface examinations (SEM) of the matrix structures and borided layers were performed. The surface hardnesses of borided samples were obtained three or four times more than that of the matrix structures. The best wear performance was observed for the sample borided at 850°C for 6 h. The mass loss of this boronizing condition is 0,2 mg and this value is nine times less compared with that of the as-cast pearlitic structure.