Interlayer of Al 2O 3–Cr functionally graded material for reduction of thermal stresses in alumina–heat resisting steel joints

Abstract

The present paper analyses the influence of an interlayer's construction and thickness on thermal residual stresses generated in ceramic–metal joints. Numerical calculations (the finite elements method—FEM) of the state of thermal residual stresses, as well as the verifying technological tests, were made for the following pair of materials: the Al 2O 3 ceramics–heat resisting steel. The model reference system was the direct joint of these materials. The results presented in this paper concern the influence of the type of a gradient material (various thickness, various construction profile—understood as the number of layers, various Al 2O 3–Cr composition and mutual position) on the state of residual stress in the joint. The numerical calculations carried out on the state of residual stresses showed that for the assumed composition and thickness of the gradient material it is possible to further lower the level of stresses in the ceramic element of the analyzed joint by modifying the profile of a gradient material's inner structure. It was found that the dangerous stresses concentration area was shifted from the bonding line ceramic/FGM layer (of relatively low strength) further into the FGM's layer, i.e. to the dividing line layer I (75Al 2O 3/25Cr)/layer II (50Al 2O 3/50Cr), of much higher strength.