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The stationary nozzle guide vanes (NGVs) and rotating blades in the turbine section are exposed to extreme temperatures as the gas released onto these parts from the combustion chamber may exceed 1600 °C (2900 °F). The turbine blades, in addition experience mechanical stresses in this severe working environment. For specific component applications, thermal spray technology is a very cost-efficient process used to protect many of these parts against heat and environmental degradation.

We Understand Blade Materials and Your Challenges

he hottest environment for components is in the first stage of the turbine. The purpose of the Nozzle Guide Vane is to redirect the airflow from gases coming out of the combustor. The function of the rotating blades of the turbine is to convert the kinetic energy of the hot gases exiting the nozzle to power that drives the compressor and provides power for the aircraft’s avionics, utilities and passenger comfort systems.

Nozzle Guide Vanes (NGVs) require a complex, multi-step coating process. A bond coat is typically applied by an electrochemical process (PtAl) or thermal spray (controlled atmosphere plasma spray), followed up by various heat treatment steps and applications YSZ top coat using electron beam physical vapor deposition (EB-PVD). The same is typically true for first stage blades. For later stages and components that see lower component temperatures and stresses, HVOF bond coats are sometimes used along with atmospheric plasma sprayed (APS) TBC top coats. For some applications the platforms of NGVs are sprayed with APS YSZ coatings and the vanes coated using EB-PVD. Design requirements are based on engine, component and service conditions.

Suspension Plasma Spray (SPS) — A Cost-efficient Technology

Suspension plasma spray is a growing technology developed in close cooperation with our customers. Its capital system costs are significantly lower than comparable EB-PVD equipment. The goal is to develop SPS coatings for component-specific applications that provide the performance of EB-PVD coatings. Justification is based on SPS coating microstructure properties, as well as the far lower capital investment costs for a thermal spray system versus EB-PVD systems. Oerlikon Metco offers the full range of SPS suspension materials, gun and feeder technology to help customers advance this technology.

Research on Tomorrow’s Solutions: Environmental Barrier Coatings (EBC)

We at Oerlikon Metco expect that environmental barrier coatings (EBCs) at some point in time will start to replace thermal barrier coatings. EBCs protect the silicon-based lighter-weight ceramic matrix composites (CMCs), particularly from the water vapor generated during fuel combustion. Besides lower weight, CMCs can operate at higher temperatures than superalloy substrates.

Oerlikon Metco has invested decades long research and will continue for future decades as well. Our objective is to optimize the material and processes to satisfy EBC requirements, for which the need of a very dense (hermetic) coating is the most challenging part of the design. With higher service temperatures, the resistance to CMAS* adds further complexity to the equation.

Oerlikon Metco is involved in the EBC development programs with several customers for proof-of-concept material chemistries and coating microstructure optimization. Our collaborations with research organizations, such as NASA, have strengthened our knowledge and experience with these complex material and application development for EBCs. Today, our materials for EBC applications, e.g., bond coats and topcoats support customer needs for their future engine coating designs.

*CMAS = Calcium Magnesium Aluminum Silicate (sand) that gets ingested in the engine, melts and solidifies on the TBC causing coating problems.

Materials and Application Development Growth: Your Total Coatings Solutions Package

Oerlikon Metco’s coating application teams work closely with OEMs and applicators to support and develop new coatings for future engines. Our knowledge and experience, not only with various thermal spray processing techniques and associated nuances, but also with optimization of motion programming for geometrically complex engine components (NGV and blades), provide a complete process solution which gives our customers a competitive edge. The unique combination of being a material powerhouse and coating application expert offers rapid development of any new coating for the engines, and is very valued by our customers.

*CMAS = Calcium Magnesium Aluminum Silicate (sand) that gets ingested in the engine, melts and solidifies on the TBC causing coating problems.

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