Study on Modification of Hydrogen Embrittlement and Hydrogen Permeability of Nb Solid Solution by W Doping

Abstract:

Doping is an effective way to eliminate the problem of hydrogen brittleness of Nb metal. Phase structure, hydride formation enthalpy, hydrogen diffusion coefficient (DH) and mechanical properties of W-doped Nb100-xWx (x=2,5,8,10,16) alloys have been investigated by XRD, SEM, PCT analysis, electrochemical method and three-point bending test respectively. The results indicated that melting-prepared Nb100-xWx samples are Nb-based solid solutions with bcc structure. W-doping will induce the lattice distortion and shrink, the distortion behavior is more obvious with the increase of W-doping content. Non-equilibrium transformation microstructure is observed in these Nb100-xWx samples, which presents dendritic morphology with W-poor region dispersed in W-rich matrix. Dense and refined dendritic morphology is observed obviously in Nb100-xWx (x=10, 16) samples. W-doping results in the increase of the value of hydride-formation enthalpy, and benefits H-release of corresponding hydride. Higher H-diffusion coefficient (DH=1.66×10-9 cm2·s-1) is obtained in Nb84W16 sample, which is about 1.8 times that of Nb98W2 sample. W-doping also improve the anti-hydrogen embrittlement capacity, Nb84W16 sample has the largest maximum load (78.4N) and maximum displacement (0.83mm), which is about 1.9 and 1.8 times that of Nb98W2 sample respectively, indicating that the improvement of mechanical properties is related to its microstructure.

Key words:Nb-based solid solution, W-doping, Hydrogen-permeation properties, H diffusion coefficient, Anti-hydrogen embrittlement