抄録
The characteristics of embrittlement in aquatic environments for austempered ductile cast iron (ADI) and as received ductile iron were investigated. Embrittlement of specimen was tested in water-based solution by a cantilever type apparatus by dropping 0.365 mass%HCl solution or ion-exchanged water of 0.013 ml/s intermittently. ADI fractured even in the ion-exchanged water when subject to high bending stress over a long period of time. Fracture strength decreased markedly in the specimen tested in the 0.365%HCl solution. These ADI fractured suddenly without creep deflection. The fracture strength of the as received ductile iron decreased slightly in the 0.365%HCl solution. In the cast iron, hydrogen generated from the galvanic reaction between the graphite and matrix in acid solution. The results suggest that the reduction of strength and ductility of ADI may be caused by hydrogen embrittlement. On the other hand, for as received ductile iron, sensitivity to hydrogen embrittlement was comparatively low because of its ferrite matrix.
