Turbine Vanes and Blades in Aerospace

In aerospace, turbine vanes and blades play a critical role in the operation of jet engines, which power commercial and military aircraft. These components are designed to operate at high temperatures and pressures, and they must be made from materials that can withstand the stresses of high-speed flight.

Turbine vanes and the different types

Turbine vanes in aerospace applications are also made from advanced materials, such as ceramic matrix composites or titanium alloys. They are designed to provide a smooth path for the hot gases to flow through the engine, while minimizing energy losses due to turbulence or flow separation.

However, there are different types of turbine vanes in a gas turbine engine: nozzle guide vanes (NGV) and turbine vanes, and they have different functions and operate in different parts of the engine.

A nozzle guide vane is a stationary component located at the entry of the turbine stage in a gas turbine engine. Its primary function is to direct and guide the flow of high-velocity hot gases from the combustion chamber onto the turbine blades. The NGV also helps to optimize the velocity and pressure of the gases entering the turbine stage, which can improve the efficiency and performance of the engine.

In contrast, a turbine vane is a rotating component that is attached to the turbine rotor. Its primary function is to extract energy from the flow of hot gases and convert it into mechanical energy that can be used to power a generator or a compressor. The turbine vane is designed to withstand the high temperatures, pressures, and stresses of the turbine stage and is typically made from advanced materials such as nickel-based superalloys or ceramic matrix composites.

From turbine vanes to turbine blades

At the same time, turbine blades are curved metal components that are attached to the rotor of the turbine. They are designed to extract energy from the hot gases by rotating in response to the flow of the gases. The blades are carefully designed to optimize their aerodynamic performance and energy extraction from the hot gases produced by the combustion process.

Both the stationary nozzle guide vanes (NGVs) and rotating blades in the turbine section of an airplane are exposed to extreme temperatures as the gas released onto these parts from the combustion chamber may exceed 1600 °C (2900 °F). In addition, the turbine blades experience mechanical stresses in this severe working environment.

In overall, these parts are exposed to very demanding environments and without the correct treatment, it might damage the perfomance of the turbine. Therefore, it is very important to put appropriate coatings on. 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.

Turbine Vane and Blade Materials and Your Challenges

The 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. Read more about us here.