Crack formation and development in thermal barrier coatings made up of functionally gradient materials

Explores the rule of formation of thermal shock cracks in thermal coatings and studies position of dangerous coating sections in thermal shocks. Functionally gradient coatings of Al/Ni-ZrO₂ are prepared on aluminum base. Formation of cracks was observed upon different thermal shocks by sudden heating and cooling cycles, using a device for thermal capability measurement. Appearances of horizontal cracks were observed after 15 cycles of thermal shock at about 80 μm above the interface between the layer of 100% ZrO₂ and that of 80% ZrO₂ and 20% Al/Ni, while appearance of segmentation cracks was observed after 50 thermal shock cycles. It is concluded that the most dangerous section lies at about 80 μm above the interface between 100% ZrO₂ and the 80% ZrO₂, where the thermal stress reaches a maximum.