Thermo-mechanical simulation of ultrahigh temperature ceramic composites as alternative materials for gas turbine stator blades

The efficiency of the Bryton cycle strongly depends on the maximum temperature of the cycle. However, restrictions on metallurgical problems deprive engineers from the benefit of high temperatures. Ultrahigh temperature ceramics can be considered in such cases, instead of traditional materials like M152 superalloy. In this study, SiC reinforced HfB₂ and ZrB₂ ultrahigh temperature ceramics were proposed as gas turbine stator blades. The heat transfer and stress-strain equations were solved numerically by the finite element method to obtain temperature and stress distributions. The results showed that the maximum thermal stress occurs in vicinity of the cooling ducts where the temperature gradient is maximum. The maximum displacements of 1.2 mm (for HfB₂–SiC) and 1.14 mm (for ZrB₂–SiC) occur in the upper wall. It can be noticed that the ZrB₂–SiC made blade showed lower maximum stress and displacement than those for the HfB₂–SiC made one, as a result of lower expansion coefficient of ZrB₂–SiC system. The addition of SiC to monolithic HfB₂ and ZrB₂ ceramics decreases their thermal conductivity and following that, the temperature uniformity in blades reduces. Although the thermal stresses and the probability of failure in these stator blades enhance, the ZrB₂–SiC material presented the best performance among the other investigated samples. Both Coulomb-Mohr and Von Mises failure analyses were employed. It was understood that both blades made of HfB₂–SiC and ZrB₂–SiC composites simply withstand the applied stresses with the safety factors of about 1.5.