Thermal fatigue resistance of alloyed, pearlitic flake, graphite irons

Twenty three compositions of flake graphite irons containing various alloying additives were produced and cast into finned, disc-shaped specimens. The thermal fatigue resistance of these specimens was determined in four different thermal cycles (700-40°C, 600-40°C, 500-40°C and 720-290°C), testing being carried out in a fully automatic thermal fatigue testing machine designed and fabricated for the purpose. Specimens were heated in a liquid neutral salt bath and cooled by either water quenching or forced air. The aim of the experiments was to obtain a better understanding of the influence of various parameters on the thermal fatigue resistance of flake graphite irons, with a view to producing materials able to meet the ever increasing demands on peak operating temperatures on flake graphite iron components subjected to repeated thermal shocks. It is concluded that the thermal fatigue resistance of flake graphite iron largely depends on graphite morphology, degree of pearlite refinement and chemical composition. High carbon irons have superior thermal resistance and alloy additions such as molybdenum, molybdenum + chromium and chromium + 3% copper impart outstanding thermal fatigue resistance to flake graphite irons.