Abstract
The relationships between the ferrite morphology and the fracture mode at low temperature have been studied about the weld metal of Fe-18Cr-8Ni type stainless steel used.
Firstly, a new etching technique was used in order to observe the three dimensional ferrite morphology. The point of technique is that the austenite matrix was preferentially dissolved at certain potential by using a potentio-statt. The electrical potential was -0.15 volt vs HgCl electrode.
Secondly, the technique was applied to fractographic observation of the fracture surface at low temperature. The results indicated that the cleavage fracture initiated at the continuous film like ferrite which caused the loss of fracture toughness. On the other hand, the dimple fracture occurred at the austenite matrix including the globular or discontinuously vermicular type ferrite.
