Maximizing the Lifespan of Gas Turbine Coatings
Eroded Gas Turbine Blade
When gas turbine coatings reach the end of their life, they lose their ability to protect the underlying metal. Coatings act as a barrier to oxidation and erosion, shielding the base material from extreme heat, corrosive elements, and abrasive particles. Over time, oxidation consumes the aluminide coatings used in turbines, forming a beta-aluminide layer. Once this protective layer is depleted, the base material is exposed to damage, leading to potential performance issues or even catastrophic failure.
Visual indicators, such as discoloration, particularly green hues, signal consumed coating. Hot spots—areas of higher heat concentration—tend to deplete the coating faster, leaving critical areas vulnerable. If left unchecked, this can result in erosion, corrosion, and material loss, significantly reducing the turbine's efficiency and lifespan.
The operating environment plays a pivotal role in how quickly a coating depletes in the hot section. High temperatures accelerate oxidation, while exposure to corrosive combustion gases increases chemical degradation. For turbines operating in extreme conditions, such as those in marine environments or power plants burning lower-grade fuels, coatings must withstand intense heat and corrosive byproducts.
Arleigh Burke-class destroyer sailing in Tokyo Bay
While external erosion from airborne particles like sand or grit primarily affects cold-section components, the hot section faces erosion from high-velocity combustion gases and molten deposits. To counteract this, coatings are specifically formulated to withstand high temperatures and chemical attack. For instance, platinum is often added to coatings to improve oxidation and corrosion resistance, while aluminum-silicon coatings help mitigate both erosion and thermal degradation, extending the coating's lifespan.
Liburdi employs a combination of advanced technologies to monitor turbine coatings and ensure they perform as intended:
Visual Inspection: Operators look for signs like discoloration, erosion, or coating cracks to identify early signs of degradation in high-temperature components.
A Liburdi Technician Performing a Visual Inspection of a Turbine Blade
Metallurgical Analysis: Destructive testing under a microscope reveals whether the beta-aluminide layer is depleted. This allows Liburdi to assess the remaining lifespan and how to best ensure strength and longevity. This can be as simple as a coating reapplication or recommending other maintenance steps.
Micrographs of Aluminide Coating in Various Stages of Degradation
Regular Maintenance: Components are routinely stripped and re-coated during scheduled maintenance intervals. This prevents coating end-of-life from allowing base material damage.
Liburdi continuously improves hot section coating technologies to meet the demands of modern turbine operations. Earlier generations of aluminide coatings degraded faster, leaving critical high-temperature components vulnerable sooner. However, newer coatings such as aluminum-silicon have greatly improved durability, consuming slower and lasting longer under extreme heat and oxidation conditions.
Platinum-aluminide coatings offer additional protection in extreme environments that accelerate degradation, particularly in corrosive settings with high-sulfur fuels or aggressive combustion gases. These advancements ensure that turbine components maintain their structural integrity and performance for more extended periods, reducing operational downtime and overall costs.
Extended Component Life: Modern coatings delay the end-of-life of hot section turbine components by protecting them from heat, erosion, and oxidation. This allows blades to be stripped, recoated, and reused multiple times, significantly extending their service life.
Optimized Performance: Maintaining the protective coating ensures that turbine components retain their shape and efficiency, resulting in better airflow and reduced fuel consumption.
Customized Solutions for Diverse Environments: Depending on the operating environment, Liburdi will recommend specific coating types, such as platinum-aluminide for extreme oxidation resistance or aluminum-silicon for enhanced durability in high-heat applications. These tailored solutions ensure turbines perform optimally in even the harshest conditions.
Avon Blades and Vanes Coated with Liburdis LSR™ Aluminide Coating
Regular maintenance is critical for turbine longevity. Stripping and recoating ensure that the base material remains protected and that any performance issues are addressed before they become critical. While modern coatings are designed for durability, no coating is permanent. Liburdi recommends regular inspections and lifecycle management to ensure turbines operate safely and efficiently.
Liburdi Turbine Services has decades of experience in extending the lifespan of hot-section turbine coatings and components. Focusing on innovation and precision, Liburdi ensures your turbines remain protected and perform at their best, even under the most demanding conditions.
For more information or to discuss your turbine maintenance needs, contact us at info@liburditurbineservices.com.
