Research On Hydrogen Embrittlement Susceptibility Of Hydrogenation Reactor Material By Small Punch Test

The small punch test (SPT) is a non-destructive test which employs a small amount of material. After more than three decades of development, it has made great progress in obtaining various mechanical properties of materials, such as yield strength, tensile strength, fracture toughness and ductile-brittle transition temperature. Based on this test method, the hydrogenation reactor of 3CrlMol/4V, which has been in service for 10 years, was investigated by hydrogen charging test and SPT. The main research work and achievements are as follows:(1) A testing device for electrolytic hydrogen charging of small punch sample and a measuring device for measuring the hydrogen content in a small sample were set up.(2) The curves of the hydrogen concentration in the samples with the hydrogen charging time and current density were obtained under different hydrogen charging parameters. It was found that when the hydrogen charging current density was constant, the hydrogen concentration did not increase with the lapse of time after the hydrogen charging time exceeded 1 hour. When hydrogen charging time is constant, the hydrogen concentration increases with the increase of the current, which would reaches the maximum at 0.06A. If the current density is continuing increased, hydrogen concentration will be a downward trend.(3) The ductile-brittle transition temperature of the four kinds of materials were obtained by SPT, including the base material, the weld and de-brittle state. It was found that the ductile-brittle transition temperature of the base metal and weld metal were both increased.(4) The microstructures of the microstructures of the microstructures after hydrogen charging were investigated. In the process of decreasing the temperature from the room temperature to the liquid nitrogen temperature, the crack propagation morphology of the specimen changed from ring shape to chevron shape and linear shape. The microstructure changed from ductile fracture to cleavage fracture, and showed the typical characteristics of hydrogen embrittlement.