Experimental Studies of Microstructure and Its Effect on Mechanical Properties of As-Cast Si-Mo-Cr Ductile Cast Iron Nanak Ram a,1 and Vijay Gautam a a Department of Mechanical Engineering, Delhi Technological University, Shahbad Daulatpur, Main Bawana Road, Delhi, India 110042. Abstract. In the present work, three heats of Si-Mo-Cr ductile cast iron with varying amounts of major alloying elements are produced. The effect of the microstructural features on the microhardness, tensile strength and ductility is studied. Increasing the nodule count decreases the pearlite-ferrite ratio, which results in a decrease in tensile strength but an increase in percentage elongation. The spherical nodule plays a significant role in arresting the crack and reorients the crack path around the nodule, as evident from the results of scanning electron microscopy. Keywords. Si-Mo-Cr Ductile cast iron, nodularity, microstructure, pearlite, ferrite. 1. Introduction The engines of modern automobiles are tested to meet the tough standards for environmental friendliness and fuel efficiency. These engines are generally smaller and run at high temperatures and with increased compression ratios [1]. The engine components are exposed to heavy thermal and thermo-mechanical loadings and therefore, the materials should possess high strength, fatigue, and scaling resistance at elevated temperatures [2-4]. The cast iron containing high silicon (Si) and high molybdenum (Mo), i.e. Si-Mo ductile cast iron(DCI), meets the requirements and maintains dimensional stability during very high fatigue cycles at temperatures ranging from freezing temperatures to greater than 750°C [5]. A higher amount of Si promotes the ferritic structure by raising the austenitic transformation temperature. Lower toughness and ductility due to the presence of carbides and pearlite in the microstructure may be improved by heat treatment [6]. The Si-Mo DCI should have lower carbon content to promote fluidity and prevent defects like cold shuts and shrinkage [7]. The automotive industry has shown its confidence in DCI through extensive use in the components 1 Corresponding Author, Nanak Ram, Department of Mechanical Engineering, Delhi Technological University, Shahbad Daulatpur, Main Bawana Road, Delhi, India; E-mail: nanak261980@gmail.com Advanced Production and Industrial Engineering R.M. Singari and P.K. Kankar (Eds.) © 2022 The authors and IOS Press. This article is published online with Open Access by IOS Press and distributed under the terms of the Creative Commons Attribution Non-Commercial License 4.0 (CC BY-NC 4.0). doi:10.3233/ATDE220809 653