Microstructure And Hydrogen Transport Properties Of Nb(W,Mo)-Ti-Ni Hydrogen Permeable Alloys

The hydrogen separation alloys Nb₄₅Ti_27.5Ni_27.5 and Nb₅₆Ti₂₃Ni₂₁ based on theory of "multiphase composition,functional sharing" have good hydrogen permeation properties,but they have insufficient hydrogen embrittlement resistance.In this paper,new hydrogen separation alloy Nb?W,Mo?-Ti-Ni were formed by using elemental W and Mo to replace part of Nb in the based alloy Nb-Ti-Ni.The microstructure and hydrogen transport properties were studied.The effects of elements W and Mo on the properties of the alloys were investigated,and hydrogen permeation materials with high hydrogen permeation properties and good hydrogen embrittlement resistance were developed.The results of XRD,SEM and EDS analysis of Nb?W,Mo?-Ti-Ni show that the main phases composition of the alloy are Bcc-Nb phase and B2-Ti Ni phase.the microstructure mainly of alloy maintains the primary Bcc-Nb phase and the eutectic phase [BccNb + B2-Ti Ni].W and Mo mainly exist in the primary phase in a solid solution,and their primary effect on the tissue is that the secondary dendritic arms of the primary phase become less developed and the eutectic phase transitions from the lamellar to the rod.The results of Hydrogen dissolution experiment show that the addition of element W or Mo can effectively reduce the hydrogen solubility of the alloy,while W and Mo have a certain synergistic effect Better than the addition of single elements,and the higher the content of added elements the more reduction of hydrogen solubility.The The results show that the addition of 5% Mo can effectively improve the permeability of the alloy,while 5% W h as little effect on the permeability of the alloy.When the addition of W and Mo each 2.5%,the hydrogen permeation performance is the best.When W and Mo each 5% will significantly reduce the permeability of the alloy.The addition of W can effectively improve the low temperature diffusion properties of the alloy,Mo can improve the high temperature diffusion performance,W and Mo 2.5% when the overall diffusion performance of the alloy has improved significantly,when the W and Mo 5% will significantly reduce the diffusion properties of the alloy.Nb40W2.5Mo2.5 Ti27.5Ni27.5 exhibits the best comprehensive hydrogen transportation performance.At 673 K,the hydrogen permeation coefficient is 3.46 × 10-8 mol H2 m-1s-1Pa-0.5,which is 1.37 times that of Nb₄₅Ti_27.5Ni_27.5 under the same conditions,which is 2.16 times of pure Pd.And The maximum hydrogen uptake at 673 K is 31.4% lower than that of Nb₄₅Ti_27.5Ni_27.5 under the same conditions,and has good hydrogen embrittlement resistance.It is found that the microstructure of?Nb,W,Mo?₅₆-Ti₂₃-Ni₂₁ alloy still maintains Biphasic structure by adding W and Mo to the Nb₅₆Ti₂₃Ni₂₁ alloy.The addition of W and Mo causes the secondary dendritic arms of the primary phase in the tissue to become less developed and the eutectic phase transitions from the lamellar to the rod.The results show that the Nb₅₆Ti₂₃Ni₂₁ alloy has good hydrogen permeation performance and poor hydrogen embrittlement resistance.The addition of equilibrated W and Mo can effectively reduce the hydrogen solubility of the alloy and improve the hydrogen embrittlement resistance,and the higher the content of the element The more obvious.The addition of W and Mo 5% can effectively improve the low temperature hydrogen permeation and diffusion properties of the alloy,and the high temperature performance is reduced.When W and Mo reach 7.5%,the alloy penetration and diffusion properties are obviously reduced.In this group of three alloys,Nb46W5Mo5Ti23Ni21 has a good overall performance,which can significantly improve the hydrogen embrittlement resistance of the alloy at the expense of partial hydrogen permeation.