Partial Constrained Sintering of Ceramic Layers on Metallic Substrates: A Comparison Between Modeling and Experiments

Abstract

Metallic substrates incorporated in multilayered systems have a nonlinear creep behavior at the sintering temperature. This behavior was taken into account in a continuum mechanical model to predict camber, densification, and stress development. Model predictions match semiquantitatively the experimental results obtained from alumina films deposited on platinum foils, which show very large camber rates at 1200°C. Such ceramic layers sintered on metallic substrates are only partially constrained, because the compatibility stresses represent only a few percent of the stress developing under perfect geometrical constraint due to creep of the platinum substrate.

Effect of the Substrate on the Constrained Sintering of BaLa4Ti4O15 Thick Films

“…(d) shows that there is a good adhesion between the film and the substrate, without delamination. This has to be contrasted with the poor adhesion of alumina layers sintered at 1200°C, which could be easily detached from similar platinum foils . Moreover, no residual porosity is left near the substrate, in contrast to that observed for alumina layers sintered on alumina substrates .…”

“…Nevertheless, no macroscopic curvature after sintering could be measured, even if the geometry of the bi‐layer is obviously asymmetrical, thus potentially leading to camber. As a comparison, 50 μm thick alumina/Pt bi‐layers showed extreme curvature values already at 1200°C, due to the important creep deformation in the metal layer . Several explanations can be given to rationalize this effect.…”

“…When the film is fully constrained, large elongated pores oriented along the thickness direction develop . Furthermore, the densification retardation commonly observed for constrained films is reduced when the multilayer is allowed to bend, for example by using platinum foil which can easily deform by creep at the sintering temperature …”

Constrained Sintering of Alumina Stripes on Rigid Substrates: Effect of Substrate Roughness and Coating

“…Such imperfections are expected to propagate throughout thermal barrier coatings by model calculations, resulting in rough film surfaces with a high propensity to mud‐cracking. Concerning the substrate material, platinum foil substrates have been found to reduce the degree of constraint of alumina films bonded to them . Warpage of these layer structures was observed.…”

Correlative Studies on Sintering of Ni/BaTiO3 Multilayers Using X‐ray Computed Nanotomography and FIB‐SEM Nanotomograhy

“…During the firing of these multilayered parts, strain mismatch between different materials that are cosintered at different rates arises and may lead to a variety of issues, including warpage, cracks, and delamination . In addition, anisotropic pore orientation and density gradients have been found in cosintered thin films and multilayers …”