The fatigue crack propagation, da/dN = C × ΔKn, in hypereutectic, permanent mold ductile iron [81808-58-4] castings containing 3.6 C and 3% Si was studied along with the effect of microstructure, such as pearlite content, graphite nodularity and count, and ferrite grain size.As-cast (chill-free) condition, mold preheating temperatures and wall thickness, austenitizing temperatures (800-1000°) were used to achieve various microstructures.The crack growth increased with increasing pearlite amount but it was not significantly affected by the graphite nodularity or ferrite grain size.The stress intensity factor range (ΔK) was improved by an increase in the graphite nodule count.A decrease in pearlite content and increase in nodule count improve the resistance to fatigue crack growth.
