A numerical study on stresses in graded multilayers during sintering and cooling

Effects of material properties and layered structures on internal stress generation in metal/ceramic graded powder compacts during firing process, which can be the cause of cracking, are studied by numerical analysis. Nonlinear variation of the sintering rate or the thermal shrinkage through the layers, due to mixing different materials, generates tensile internal stresses on the surface of the top ceramic layer. To extinguish the tensile stresses in both sintering and cooling periods together by adjusting the graded structure, a way of modifying the sintering properties is clarified. The multilayer is converted into the equivalent, essential three layers on calculation, for ease. Decreasing tensile bending stress and increasing compressive mismatch stress on the surface, by relatively gaining the sintering rate as well as the thickness of the middle layer, can be a solution for surface cracking during sintering, and may not conflict with design for thermal stress relief.