APPARATUS FOR MATERIALS TESTING IN HIGH-PRESSURE HYDROGEN AT LOW-TEMPERATURES

A new type of apparatus for materials testing in high-pressure hydroge n up to 10 MPa at low temperatures down to 20 K was developed. The app aratus consists of the pressure vessel, cooled by a two-step external cooling method, and the hydraulic loading system. In the first cooling step the specimen in the pressure vessel is cooled to 84 K using a co oling tube between the coolant shroud filled with liquid nitrogen and the pressure vessel. In the second cooling step the specimen is cooled to 20 K using a helium refrigerator. The apparatus is designed to mea sure the actual load on the specimen with an external load cell irresp ective of the axial load caused by high pressure and friction at the s liding seals. As an example of the application of the apparatus, the t ensile properties of type 304L stainless steel in 1 MPa hydrogen and h elium at low temperature are measured and hydrogen environment embritt lement of the steel is briefly discussed. (C) 1997 American Institute of Physics. [S0034-6748(97)03311-X].