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In this paper, the effects of copper addition (0–2.0 wt.%) on the microstructure and properties of carbidic austempered ductile iron were studied using an optical microscope, a scanning electron microscope, a Rockwell hardness tester, a pendulum impact tester, an X-ray diffractometer, a block-on-ring wear testing machine and an electrochemical tester. The amount of carbides and graphite nodules simultaneously decreased with the increase in Cu content. Cu also improved the nodularity of graphite, made the graphite nodules grow, increased the pearlite content and refined the pearlite. After austenitizing (900°C / 100 min) and austempering (300°C / 100 min), the amount and size of the acicular ferrite significantly reduced with the addition of Cu. In contrast, the amount of retained austenite dramatically increased, and the carbon content in retained austenite slightly increased. The hardness of carbidic austempered ductile iron had no obvious change with the increase in Cu content. The wear resistance of carbidic austempered ductile iron first increased and subsequently decreased, and the impact toughness and corrosion resistance were improved with the increase in Cu content. The comprehensive properties of carbidic austempered ductile iron were optimal, with the Cu content of 1.0 wt.%.

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In the present study, the authors investigated the effect of the austenitizing temperature (860 to 1020 °C) on the microstructure evolution, hardness, wear resistance and corrosion resistance of Cu-bearing carbidic austempered ductile iron (CADI) by means of an optical microscope (OM), a scanning electron microscope (SEM), a Rockwell hardness tester, a microhardness tester, an X-ray diffractometer (XRD), a block-on-ring wear testing machine and electrochemical tester. The results show that with an increase in the austenitizing temperature, the amount of acicular ferrite decreases, size expands, and the volume fraction of high-carbon austenite increases gradually as does carbon content. Part of the carbide dissolves into the matrix, and the amount is significantly reduced. The hardness of Cu-bearing CADI first increases and subsequently decreases, and the hardness is highest at 940 °C. With an increase in austenitizing temperature, the wear loss of Cu-bearing decreases and its wear resistance increases. When the austenitizing temperature is 940 °C, wear loss is lowest and wear resistance is optimal. Electrochemical corrosion experiments show that as the austenitizing temperature increases, the corrosion potential of Cu-bearing CADI is slightly improved, the corrosion current density is gradually reduced, and the corrosion resistance of Cu-bearing CADI is improved. Considered comprehensively, the austenitizing temperature of Cu-bearing CADI should be determined to be 940 °C.