Microstructure and properties of Cu-bearing carbidic austempered ductile iron

Abstract

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.%.

Improved corrosive wear resistance of carbidic austempered ductile iron by addition of Cu

“…The amount of retained austenite of CADI for different Cu content was calculated by the method from Ref [5,15], and the results showed that the amount of retained austenite gradually increased from 21.3 % to 26.9 % with the rise of Cu content from 0 wt.% to 2 wt.%. After adding Cu, the rate that undercooled austenite transformed into bainite was decreased [15,23], which led to the increase of retained austenite. The volume fraction of carbides was measured by the analysis of OM images with an Image-pro software.…”

“…The properties (e.g. hardness, impact toughness, tensile strength, and wear resistance) of carbidic austempered ductile iron (CADI) have been significantly improved after several works regarding processing design and composition control [11][12][13][14][15]. CADI is widely applied in the engineering field [16].…”

Simulation on stress of large diameter CADI grinding ball based on ANSYS

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C ADI (Carbidic Austempered Ductile Iron) is a new kind of wear-resistant material developed on the basis of ADI [1] (Austempered Ductile Iron). There are many studies concerning CADI, such as on chemical composition [2][3][4][5] , microstructure [6,7] , properties [8][9][10][11] and heat treatment [12][13][14][15] . The matrix structure of ADI is composed of the acicular ferrite with high hardness, and the strong and ductile retained austenite.

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