Tensile and Thermal Properties in Compacted Graphite Irons at Elevated Temperatures

Tensile and thermal properties of compacted graphite irons (CGIs), prepared with various molybdenum additions and solidification rates, have been investigated for temperatures between room temperature and 873 K (600 °C). A slower solidification rate resulted in larger and fewer graphite particles as well as in an increase of intercellular cementite, or carbides. Molybdenum is a carbide stabilizing element; i.e., increasing additions of molybdenum increased the amount of carbides. Young’s modulus decreased with increasing temperature, and a lower solidification rate increased this parameter slightly. Both increasing content of carbide and increasing nodularity increased the Young’s modulus. Strength parameters such as yield strength and ultimate tensile strength (Rm) were affected in similar ways by temperature and solidification rate. The strength values were generally quite temperature independent for temperatures below 573 K (300 °C) but decreased rapidly for higher temperatures. Increasing nodularity increased the strength, while increasing content of carbide had little influence on the values. The thermal conductivity decreased with increasing content of carbide and increasing nodularity. The thermal conductivity generally showed a maximum value at 573 K (300 °C). A contradictory linear relationship was found between yield strength and thermal conductivity.