Effect of SiC microfibers as a self-healing agent and their influence on oxidation and adhesion resistance of thermal barrier coatings exposed to cyclic thermal oxidation treatments

Abstract High-temperature coatings are commonly used in components working at high temperatures, such as turbine blades and combustion chambers to increase their efficiency. The durability of the high-temperature coatings is governed mainly by the growth of the thermally grown oxide (TGO) layer. In the present study, the effect of the addition of SiC microfibers on microstructural stability, adhesion and oxidation resistance of thermal barrier coatings (TBC) subjected to thermal cycles at high temperature was investigated. High-velocity oxy-fuel (HVOF) and air plasma spraying (APS) thermal spraying processes were used to produce bond coat (BC-NiCoCrAlY) and ceramic (yttria-stabilized zirconia-8YSZ) respectively. The adhesion test was determined accordingly to ASTM-C-633 Standard Test Method for Adhesion or Cohesion Strength of Thermal Spray Coatings. X-ray diffraction (XRD), scanning electron microscopy (SEM) techniques were employed to characterize the morphology, microstructure, and phases of the coatings. After 10 cycles at 25 h at 1100 °C, reinforced samples with 3 wt% SiC microfibers showed better oxidation resistance compared to those without the addition of SiC microfibers. Also, was noted that Si compounds were distributed along some cracks at the interface of the TGO-TBC, enhancing its adherence.