An experimental investigation in effects of thermal fatigue and constant bending loading on failure of a sample of thermal barrier coatings

In this study, the effects of thermal cyclic loading in the presence of a constant mechanical load were evaluated experimentally on failure of thermal barrier coatings. For this purpose, specimens of Inconel 617 with approximate dimensions of 100×10×6.2 mm that coated by two-layered thermal barrier coatings include a Ni22Cr10Al1Y bond coat and ZrO2.8wt%Y2O3 using air plasma spraying (APS), were considered. These specimens were tested under low cycle thermal fatigue experiment with maximum temperatures of 1000oC, 1100oC and 1170oC for thermal cycles and constant bending loads of 4500 Nmm, 6000 Nmm, 7500 Nmm and with no load by using a made test rig with the ability of four point bending load. In a thermal cycle, a specimen heating time was 10 minutes and cooling time was 5 minutes approximately. The results obtained in this study, showed that different loads change thermal barrier coatings failure mechanisms and service life cycles of coating reduce exponentially by rising maximum temperature of thermal cycle. Also increases in mechanical load have significant effect on the reduction of thermal barrier coatings life during thermal fatigue loading.