Deformation, Internal Stress and Delamination during Co-Sintering of Metal-Ceramic Laminates

During the co-sintering process of MCLs, undesirable deformations often occur, frequently leading to delamination, curvature, crack formation or even complete fracture. Experimental work to determine the possible causes of fracture relies heavily on the time-consuming principle of "trial and error". However, the interaction of multiple events makes it difficult to analyse the causes and failure mechanisms from an experimental point of view. The main objective of this work is to develop a thermo-mechanical–metallurgical model which is capable of predicting the densification, deformation and delamination of MCLs during the co-sintering process. In addition, this work aims to gain a better understanding of the causes of delamination during the co-sintering process by analysing the evolution of internal stresses in MCLs based on the developed model. To achieve these objectives, the inhomogeneous relative density distribution and the phase transformation of the steel tape are successfully considered in the newly developed model. Furthermore, the mixed inter-layer in MCLs is modelled as cohesive elements to simulate the delamination process. The developed model is systematically validated by experimental measurements and observations. It is found that the developed model is able to predict the densification, deformation and delamination of the investigated laminate variants during the co-sintering process with a satisfactory accuracy. Phase transformation accompanied by volume change plays a crucial role in the occurrence of delamination when the interface is weak. At high sintering temperatures, on the other hand, delamination does not proceed due to complete stress relaxation despite large differences in sintering shrinkage.