Influence of Thermal Degradation on the Mechanical Properties of Coatings [8YSZ/Al2O3]n Subjected to Thermals Cycles

Abstract

This study is based on the thermal degradation presented in the multilayer coatings [8YSZ/α-Al2O3]n when subjected to thermal cycles, focusing mainly on the analysis of the mechanical properties before and after these. To determine thermal degradation, the coatings were analyzed by XRD before and after thermal cycling. From these results, the presence of a tetragonal phase and an alpha phase belonging to (8YSZ and Al2O3) respectively was determined before the thermal cycles. After the cycles, show new peaks attributed to 2 important factors, the appearance of a monoclinic and cubic phase belonging to 8YSZ and peaks due to the presence of substrate oxides produced by a delamination of the coating and that decreased in intensity as increase in the bilayers number. Mainly, it was determined for the 70 bilayers coating, which presented the best mechanical properties before the thermal cycles, a decrease of 34.44% and 6.41% for hardness and elasticity modulus respectively, after the thermal cycles. From this research, it was concluded that the coating [8YSZ/α-Al2O3]n with 70 bilayers, presented the highest resistance to thermal wear generated in the coatings.