Effect of Graphite Phase on the Water-Assisted Deterioration in Vibration Fracture Resistance of Ferritic Spheroidal Graphite Cast Iron

摘要

The vibration fracture behavior of various ferritic spheroidal graphite cast irons was investigated in different ambient environments. The overall D-N curve is strongly ambient environment dependent and can be generalized into three characteristic regions. Significant deterioration of vibration fracture resistance of ferritic S.G. cast irons can be attributed to the effect of an aqueous ambient environment. Increases in the graphite area fraction and the coarsening of graphite nodules will intensify the water-assisted deterioration. Patterns observed on the fractograph demonstrate that vibration loading can cause intergranular fractures in the vicinity of the surface, and many intergranular cracks could be seen around the graphite nodules. The intergranular fractures became deeper as the area fraction or nodule size of the graphite phase was increased. This provides further evidence that the water-assisted deterioration of vibration fracture resistance is closely related to the nodular graphite phase.