Enhanced hydrogen embrittlement of Pd-coated niobium metal membrane detected by in situ small punch test under hydrogen permeation

The hydrogen embrittlement of pure niobium metal membrane was investigated under a hydrogen atmosphere by using a newly developed in situ small punch apparatus. The boundary for the ductile-to-brittle transition of the palladium-coated pure niobium was determined from a series of the in situ small punch tests. The measured boundary was found to be shifted greatly to the lower hydrogen content region as compared to that of palladium non-coated niobium membrane. The present result will provide us a clue to the design of niobium-based permeable membrane against the hydrogen embrittlement.