Abstract: 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-ZrO 2 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% ZrO 2 and that of 80% ZrO 2 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% ZrO 2 and the 80% ZrO 2, where the thermal stress reaches a maximum.