The objective of this study was to ensure the safety use of brazing parts of Coriolis flowmeter in high-pressure hydrogen gas. Thermal desorption analysis measured that the hydrogen diffusion coefficient of brazing filler metal, Ni-30Cr-4Si- 6P, was one third as small as that of the material of brazed pipe; austenitic stainless steel, XM-19 (HRX19). In order to investigate the effects of hydrogen on the strength of brazed parts, four types of tensile tests using brazed specimen were conducted as follows: (i) test of non-charged specimen in air, (ii) test of non-charged specimen in 0.7-MPa hydrogen gas, (iii) test of non-charged specimen in 95-MPa hydrogen gas, and (iv) test of hydrogen-charged specimen in air. The fracture was occurred from the brazing parts in all the cases, and the tensile strengths obtained were nearly the same in all the cases, i.e. the tensile strength was not degraded due to hydrogen.
Ceramic/metal brazing was investigated to produce light-weight and highly-efficient ceramic thrusters. Silicon nitride ceramic and metal bars were brazed using an Ag-based brazing material. Four-point bend tests were conducted at room and high temperatures to evaluate the strength of the brazed joints. Computational fluid dynamics (CFD) and finite element method (FEM) analyses were also performed to investigate the effect of the construction and shape of the joints on the stress distribution around them. It was demonstrated that brazing was a great candidate as the joining technique, and a 20 N ceramics/metal brazed thruster was successfully produced.