Abstract
Researches on the hydrogen embrittlement of Ni and Ni based alloys in which phase transformation does not occur are reviewed. Characteristics of hydrogen diffusion, influence of hydrogen on the flow stress and the fracture mechanism of hydrogen embrittlement are discussed. Plastic deformation seems to play an important role in hydrogen embrittlement of Ni and Ni alloys in comparison with that of iron and steels. In spite of many efforts, however, the fracture mechanism of hydrogen embrittlement has been under the discussion. Then, different approaches may be needed.
