Mechanism of High Temperature Environmental Assisted Cracking by the Forward Processing of Dissipative
Kentaro Hayashi, Mikio Takemoto
AE monitoring of the sensitized and non-sensitized SUS 304 steels exposed to the molten mixed chlorides (30mol%PbCl2+30%FeCl2+20%NaCl+20%KCl) at around 600°C was attempted utilizing the new heat-resistant AE monitoring system developed in the first paper. AE waves or out-plane displacements, indicating the fast Mode-I and -II crackings, were reproducibly monitored for both the sensitized and non-sensitized SUS 304 steels. Crack generation rate estimated by the forward signal processing with accounting the wave attenuation and the responce delay of the sensor was found to be faster for the sensitized steel than that for the non-sensitized steel. The maximum crack rate for the Mode-I and -II fracture, respectively, reaches 35 and 170m/s for the sensitized SUS 304 steel at 600°C under the applied stress of 157MPa. These fast cracks are assumed to occur isolately in time and space. Possible mechanisms for such fast crackings are discussed in relation to the grain boundary decohesion.