THERMAL SHOCK RESISTANCE AND ABLATION BEHAVIOUR OF TITANIUM DIBORIDE-COPPER-NICKEL CERMET

Titanium diboride-copper-nickel cermet was fabricated from titanium, boron, copper and nickel powders by combustion synthesis under conditions of pseudo hot isostatic pressing. The TiB₂-Cu-Ni cermet was heated by using a plasma torch to investigate the thermal shock resistance and ablation behaviour. The microstructures of the cermet pre- and post-ablation were examined by SEM, EPMA and EDX. The result shows that the thermal shock resistance of the cermet is good, and the cermet does not burst apart when the material is instantly heated. However, a macro-crack is immediately formed on the surface of cermet when the ablation is just over. The mass loss of cermet after ablation for 20 s is 0.9 g and the mass loss ratio is 0.045g/s, which shows a good ablation property of the material. The ablation mechanism of TiB₂-Cu-Ni cermet is the volatilization of metal binder, hot chemical ablation and mechanical erosion.