Wear resistance of high nodule count ductile iron

Thin wall ductile iron (DI) is being used in the industry as a way to improve the strength to weight ratios. The high cooling rate, suffered by thin walled parts as they solidify, promotes several micro-structural changes, such as, carbide precipitation, casting defects and a noticeable nodule count increment. The present work studies the effect that the increase in nodule count has on the resistance to abrasive and rolling contact fatigue (RCF) wear. Ductile cast iron test samples, with nodule counts varying between 100 and 1500 nod/mm2 were employed. The samples for abrasion tests were previously ferritized and then their wear resistance was evaluated according to the ASTM G 65 standard. The samples used in the RCF tests were first austempered and then evaluated by using a flat washer type test rig. The results show that an increase in the nodule count promotes an increase in the abrasive wear rate. Otherwise, under the RCF wear mechanism, the high nodule count was highly beneficial, promoting a noticeable life increment of about six times.