Compacted Graphite Iron: New Opportunities for Engine Design

Compacted graphite iron (CGI) provides at least 70% higher tensile strength, double the mechanical fatigue strength, and 30-40% higher elastic modulus (stiffness) than conventional grey cast iron. In comparison to the common aluminium alloys, compacted graphite iron provides double the strength and stiffness at room temperature and approximately three times higher mechanical fatigue strength. At operating temperatures of 300°C, the fatigue strength of CGI is more than five times higher than that of the common aluminium alloys. The dramatic increase in the strength of CGI relative to grey iron and aluminium provides many new design opportunities with regard to the reduction of engine weight and size, and improvement of critical operating parameters such as long-term dimensional stability, wear resistance and NVH. In addition to the many operational benefits, compacted graphite iron allows for continued use of existing grey iron foundries and machining lines with little or no capital cost requirements. CGI also provides critical advantages over lightweight materials by allowing well established ferrous metal recycling routines to be maintained along with the favourable economic profile of cast irons.

The purpose of the present paper is to provide a brief introduction to compacted graphite iron and to present the results of various engine performance tests conducted by end users around the world.