Phase transformation and microstructural development of zirconia/stainless steel bonded with a Ti/Ni/Ti interlayer for the potential application in solid oxide fuel cells

Abstract

The 8 mol% yttria-stabilized zirconia (8Y-ZrO2) was bonded to stainless steel 316L at 900 degrees C for 1 h in a protective Ar atmosphere using an interlayer of Ti/Ni/Ti. Interfacial microstructures were characterized using both secondary electron microscope (SEM) and transmission electron microscope (TEM), each with an attached energy dispersive spectroscope (EDS). A layer sequence of sigma-phase/TiFe2/TiFe + beta-Ti/Ti2Fe was observed at the stainless steel 316L/Ti interface, whereas a layer sequence of Ti2Ni/Ti2Ni + TiNi/TiNi3 was found at the Ti/Ni interface. Furthermore, TiO and c-ZrO2-x formed at the Ti/8Y-ZrO2 interface. An acicular alpha-Ti and a fine omega-phase existed along with beta-Ti in the residual Ti foil adjacent to the stainless steel 316L, but alpha-Ti and Ti2Ni were observed within beta-Ti in the other residual Ti foil adjacent to the 8Y-ZrO2. The orientation relationships of the omega-phase and beta-Ti were ${left[ {1bar 10} right]_{{rm{ beta {hbox-} Ti}}}}//{left[ {1bar 210} right]_{rm{omega }}}$ and ${left( {111} right)_{{rm{beta {hbox-} Ti}}}}//{left( {0001} right)_{rm{omega }}}$ , respectively. The microstructural development was elucidated with the aid of Fe-Ti and Ni-Ti binary phase diagrams.