種々な水素発生電位下におけるSUS430ステンレス鋼の破面形態

Abstract

The morphology of fracture surface due to the hydrogen embrittlement indicates the different fracture surface by the state of applied stress, environments and materials. In the first step to elucidate the mechanism of hydrogen embrittlement, the slow strain rate tension tests were carried out under various hydrogen evolution potentials on the cathodic polarization curve which was obtained in 3% NaCl solution. This study was aimed to compare and examine the relation between the setting potential and the morphology of fracture surface. The main results obtained are summarized as follows. (1) The commencement potential of cathode reaction in SUS430 has turned out to be shifted until -0.5V (vs. S. C. E.) with increasing tensile stress also from the SEM observation. That is to say, the morphology of fracture surface in this potential have analogy with those in atmosphere. (2) The hydrogen embrittlement fracture surface of SUS430 due to the cathode reaction in 3% NaCl solution indicates the transgranular fracture or Quasi-cleavage fracture at the outside region of specimen. In addition, the micro crack result from degradation of grain binding force formed at the surface vicinity layer of specimen. This tendency is more pronounced in the conditions of lower setting potential and lower strain rate. Macroscopic rupture progress toward the internal region from the outside of specimen.