Thermal fatigue characteristics of plasma duplex treated nodular cast irons

The correlation between the thermal fatigue resistance and microstructure of untreated and plasma surface engineered nodular cast irons was investigated. Both the ferrite and pearlite matrix nodular cast irons were evaluated. During the tests, 60 mm long cylinders with 20 mm diameter were subjected to 1000 high frequency induction heating and water cooling cycles, lasting 7 and 5 s, respectively. The thermal fatigue damage was evaluated by analyzing the crack dimensions and distributions. The results showed that the plasma surface treatment increased thermal fatigue resistance. When thermal cracking occurred, the cracks always nucleated at the surface of the specimen. In addition, the nodular cast iron with a pearlite matrix had a better resistance to thermal fatigue than that of the ferrite matrix.