RETRACTED: Influence of cobalt phase on thermal shock resistance of Al2O3–TiC composites evaluated by indentation technique*

Cobalt-coated Al 2 O 3 and TiC powders were prepared using an electroless method to improve resistance to thermal shock. The mixture of cobalt-coated Al 2 O 3 and TiC powders (about 70 wt.% Al 2 O 3 ¯Co + 30 wt.% TiC-Co) was hot-pressed into an Al 2 O 3 -TiC-Co composite. The thermal shock properties of the composite were evaluated by indentation technique and compared with the traditional Al 2 O 3¯ TiC composite. The composites containing 3.96 vol.% cobalt exhibited better resistance to crack propagation, cyclic thermal shock and higher critical temperature difference (∇T c ). The calculation of thermal shock resistance parameters (R parameters) shows that the incorporation of cobalt improves the resistance to thermal shock fracture and thermal shock damage. The thermal physic parameters are changed very little but the flexure strength and fracture toughness of the composites are improved greatly by introducing cobalt into Al 2 O 3¯ TiC (AT) composites. The better thermal shock resistance of the composites should be attributed to the higher flexure strength and fracture toughness.