Preparation, microstructure and mechanical properties of SiC-SiC and B4C-B4C laminates

Silicon carbide and boron carbide are high hardness materials with a low density but, like most ceramics, with a low toughness, that limits their use in various applications. One approach to reinforce ceramic materials consists in using crack deflection by weakening the interfaces in laminar materials. In our study, ceramic layers of different compositions were prepared by tape casting and stacked in predefined sequences. Different weak layers were tested: porous layers made with different pore forming agents for SiC; porous layers made with pore forming agent or by varying the quantity of sintering aid and weak interfaces made with graphite spray for B4C. After debinding, SiC (Al2O3, Y2O3 additions) and B4C (C addition) were pressureless sintered. For evaluation of the sintered parts, firstly the macrostructure and microstructure were characterized. Then, mechanical properties of multi-layered materials, obtained by stacking dense and porous layers that should contain enough porosity to initiate crack deflection, according to the models, were evaluated