Investigation of Hot Section (Nozzle Guiding Vane) Distress due to Interaction of Thermal Barrier Coatings with CMAS

Abstract

An investigation of distress of hot section nozzle guiding vane (NGV) was carried out. Thermal barrier coatings (TBCs) were applied to the components of gas turbine engines to operate at higher temperatures i.e. up to 1200°C. The cause of failure was hot corrosion of TBCs by chemical entities from atmosphere like oxides of Al, Ca, Si and Mg (CMAS). Source of CMAS was dust, which was ingested to airfoil engine components. Different techniques like scanning electron microscope, boroscopy, optical microscopy, X-ray Diffraction and optical emission spectroscopy were utilized to investigate the failure of nozzle guiding vanes.

CMAS Corrosion Behavior of Nanostructured YSZ and Gd-Yb-Y-Stabilized Zirconia Coatings

“…A transition from the t'-ZrO 2 to the m-ZrO 2 can be found during cooling, probably due to the reduction of stabilizers in YSZ and n-YSZ coatings under CMAS exposure (Figure 4a,b). Unfortunately, this phase transition adversely affects the service life of the coatings [49]. In contrast, there is no phase transition in GYYSZ coatings under the same conditions (Figure 4c).…”