Wear, 113 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA (1986) 267 - 278 267 EROSION BEHAVIOR OF HIGH SILICON BAINITIC STRUCTURES I: AUSTEMPERED DUCTILE CAST IRON S. M. SHAH* and J. D. VERHOEVEN Department of Materials Science and Engineering, Ames Laboratory, Iowa State University, Ames, IA 50011 (U.S.A.) S. BAHADUR Department of Mechanical Engineering, Iowa State University, Ames, IA 50011 (U.S.A.) (Received December 17,1985; accepted March 24,1986) summary The erosion behavior of unalloyed austempered ductile cast iron has been studied as a function of austempering time for irons austempered in the upper bainitic temperature range (370 “C). A minimum erosion rate and iron matrix hardness occurs at the end of the stage II austempering time, where the microstructure consists of bainitic ferrite and retained austenite. Experiments show that erosion induces transformation of retained austenite at early times of stage II austempering and that maximum erosion resistance correlates with maximum work hardening of the substrate during the erosion process. Scanning electron microscopy studies of the eroded surfaces and the substrate revealed that the material removal in erosion occurs because of the cutting, ploughing and flake formation mechanisms which depend upon the microstructures and their mechanical properties. 1. Introduction The remarkable combination of properties attainable from austempered ductile cast irons has made them emerge lately as a new class of ductile cast irons. The matrix of these irons is composed of bainite together with retained austenite and graphite. The morphology and the proportions of these microstructures govern the mechanical properties. Austempered cast irons have been reported to be twice as strong as the standard ductile cast irons grades at the same level of toughness [l] and are also known to exhibit greater impact strength, fatigue strength and sliding wear resistance [ 2 - 51. Because of their low production cost, austempered ductile irons have been increasingly used for industrial parts such as hydraulic valve bodies, exhaust systems, automotive gears, cylinder heads and many others. In some of these applications, erosion is an important problem and although the mechanical *R.esent address: General Motors Technical Center, Warren, MI, U.S.A. 0043-1646/86/$3.50 @ Elsevier Sequoia/Printed in The Netherlands