Phase formation during sintering of nanocrystalline zirconia/stainless steel functionally graded composite layers

Microstructural development and phase formation at the interface of yttria stabilized zirconia (3Y-TZP)/430L stainless steel composite layers produced by co-sintering method were studied by SEM, HRTEM, micro-focus XRD, and EPMA. Formation of a rich chromium boundary layer at the interface was noticed, which revealed Cr aggregation at the interface at the elevated temperatures. Misfit dislocations were also observed at the joint interface to tackle the mismatch crystallographic orientations between the ceramic and metal layer. The results of the micro-focus XRD showed formation of no new phases at the boundary zone. Microstructural studies also revealed a retarded grain growth in the nanostructured zirconia due to the pinning effect of ultra-fine pores located at the grain–boundary junctions. The shear strength of the ceramic/metal joint was found to depend on the sintering atmosphere and varied in the range of 47–66 MPa.