Steam turbine coatings and stelliting
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Degradation of the surface finish of airfoils can drastically reduce steam turbine efficiency. The same is true for changes to the throat area due to buildup from fouling, as well as material loss from corrosion and erosion. Sulzer offers coatings to protect against wear.
Sulzer offers coatings and Stellite® hard-facing designed to reduce losses in efficiency and help maintain steam turbine performance.
- Air spray coatings such as A21 and A24 protect airfoils against corrosion and reduce fouling. These metallic-ceramic coatings improve and maintain surface finish.
- Each coating contains an aluminum-chromate-phosphate base coat to provide sacrificial cathodic protection from corrosion.
- The active coating layer acts as an anode to protect the less active base metal. An inorganic sealer improves surface finish and extends the life of the coating.
- A24 contains a third inorganic layer impregnated with Polytetrafluoroethylene (PTFE) to provide anti-fouling characteristics.
- Thermal spray coatings, such as High Velocity Oxygen Fuel (HVOF) chrome carbide, improve erosion protection.
- Chrome carbide coatings have a hardness level over 60 HRc.
- Stellite® and other hard facings can also be coated, welded, or brazed onto steam turbine blades in order to resist erosion.