Protect your turbine with a good coat
Thermal Barrier Coatings (TBCs) protect the first several rows of hot gas path parts from the high combustion temperatures in many advanced large frame turbines. Not all coating applications are equal, and some can even reduce the efficiency of your unit.
TBCs are designed to reduce the temperature of the buckets and stators while providing resistance to corrosion and reducing oxidation of the component. TBCs form aluminum-oxide and chromium-oxide scales and act as a physical barrier to reduce component temperatures, extending the life of the parts. These TBCs are subjected to mechanical stresses, and spallation (coating separation) can occur. If a significant amount of TBC has separated from the metal, the parent metal will be exposed to the hot combustion gases and component degradation will be accelerated.
Hot gas path components should be inspected for TBC spallation at every Hot Gas Path or Major outage. Streaks of brown lines that appear to be coming from the cooling holes are a good sign that the component is receiving adequate cooling air, and spallation is at a minimum. When receiving components from the repair shop it is important to carefully inspect the components for an even coat of TBC. Also inspect the cooling air passages for debris and proper sizing to ensure that proper air flow can pass through the tiny passages for designed cooling.