Effects of Copper and Austempering on Corrosion Behavior of Ductile Iron in 3.5 Pct Sodium Chloride
- PDF / 1,004,017 Bytes
- 7 Pages / 593.972 x 792 pts Page_size
- 90 Downloads / 231 Views
DUCTION
IT is well known that ductile irons have been widely used in many industrial areas worldwide such as pressure pipes, agriculture, automotive and machine parts, and so on. In recent years, ductile iron has been identified rapidly as the right material for many wind mill parts, because of its major advantages, such as higher castability, lower density, and improved machinability, versus steel, in addition to offering the required mechanical properties.[1] The material can acquire various desired mechanical properties through alloy addition and/or heat treatment. For example, the addition of alloying elements, such as copper, nickel, cobalt, and molybdenum, can change the microstructure of ductile irons and increase fatigue strength and fracture toughness.[2,3] Also, ductile irons via austempering treatment can form acicular ferrite and retained austenite in microstructure; hence, the unique microstructure allows the material to have the excellent strength and wear resistance comparable with wrought steels while retaining the low cost and design flexibility of cast irons.[4] Austempered ductile irons (ADIs) are the subject of much R&D with current emphasis on heavy machinery and transportation equipment.[5,6] Despite this trend, most studies have focused on the exploration of mechanical properties; related information on the corrosive property of the material appears to be limited. Ductile irons are economic in service, but the material corrodes under certain applied environments containing chlorine medium.[1] Therefore, this becomes a significant
CHENG-HSUN HSU, Professor, and KUAN-TING LIN, Graduate Student, are with the Department of Materials Engineering, Tatung University, 40 ChungShan North Road, 3rd Sec, Taipei 10451, Taiwan, ROC. Contact e-mail: [email protected] Manuscript submitted April 25, 2013. Article published online October 18, 2013 METALLURGICAL AND MATERIALS TRANSACTIONS A
challenge while attempting to improve the corrosion resistance of ductile iron parts assembled in the wind power requirements along the seashore. Previous studies[7,8] found that ADI with copper addition improved toughness while nickel addition improved corrosion resistance. This study aims to explore the combinatory effect of copper addition and austempering treatment on the corrosion behavior of ductile irons, to understand the relationship between both the processing factors and the corrosion protection on the iron.
II.
EXPERIMENTAL PROCEDURES
A. Material Preparation and Austempering Treatment Y-block ductile iron castings of 30-mm thickness were produced for this study. The experimental irons were divided into two groups: unalloyed ductile iron (DI), and 1 wt pct copper alloyed ductile iron (1 pctCu-DI). To produce the 1 pctCu-DI, pure copper wires were added in the ladle and fully stirred before pouring the molten metal into green sand molds. Nodularizer and inoculant were added in 1.1 and 0.3 wt pct, respectively, in the casting process. Chemical compositions of the nodularizer, the inoculant, and the experimental irons
Data Loading...
