TiC-TiN-Mo₂C-WC-HfC-Cr₃C₂多元系複合セラミックスの強靭化機構

抄録

It has been confirmed that the dense multi-component ceramic composites consisting of 40% TiC-15% TiN-4%Mo₂C-25%WC-8%HfC-8%Cr₃C₂ showed strengthening and toughening with accompanied grain growth according to rise of sintering temperature up to 1873K, in the same way as in TiC-TiN-Mo₂C-Cr₃C₂ ceramic composite of previous work. That is to say, the toughening was occurred by multi-toughening mechanism comprising branching and deflection of cracks and micro-cracking.
Among these energy absorbing phenomena in crack propagation, branching of cracks and micro-cracking were more occurred in the composite than previous one, resulting higher fracture toughness. It was presumed that the higher fracture toughness was caused by increase in Young's modulus of matrix and enlargement of difference in thermal expansion coefficients between matrix and low chromium carbide particles, due to addition of large amounts of tungsten carbide in the composite. The fracture toughness showed good correlation with calculated sizes of plastic zone formed at tip of cracks in the both composites.
It was also clarified that strengthenings in the both composites were depending not on decrement of defect size but on enhancement of fracture stress based on R-curve behaviour.