Coatings for steam and industrial gas turbine blades and vanes

Hardide CVD coatings provide unrivalled protection for steam and industrial gas turbine (IGT) blades and vanes against damage by water droplet erosion (WDE), corrosion and solid particle erosion.

The combined protective properties of Hardide coatings increase the service life and extend the optimal performance of these turbine components further than any other coating technology.

Coatings for water droplet erosion and corrosion protection

Turbine blades and vanes are critical components of both steam and gas turbines.

To achieve optimum aerodynamic performance, the blades have an aerofoil shape and an optimal surface finish. During operation, the blades often move at a speed close to or exceeding the speed of sound, and are exposed to erosion from high-speed water droplet and solid particle impacts, which result in material loss and roughening of the turbine blade surface causing an increase in drag and loss of turbine efficiency. Blades and vanes often have to be replaced at maintenance intervals due to erosion and/or corrosion issues.

Hardide Coated Turbine Blade

Gas turbine efficiency is often improved by introducing water mist into the gas flow at the turbine inlet to increase the mass flow and the efficiency of the compressor. Compressor blades operating with this inlet fogging can suffer from WDE, as can the last rows of steam turbine blades where expanding steam produces water condensation. WDE damages the leading, and sometimes trailing edges, of steam and gas turbine blades, increasing turbine rotation drag, reducing efficiency and incurring costly blade and vane maintenance.

Hardide-A and Hardide-T coatings significantly improve resistance to WDE, extending blade and vane life. In testing by the UK National Physical Laboratory (NPL), Hardide-A and Hardide-T showed at least a x10 fold longer WDE incubation stage compared with uncoated 410SS.

Unlike PVD coatings for turbine blades and vanes, Hardide coatings are also highly corrosion resistant being pore-free, 10x thicker and more ductile.

Enhanced high cycle fatigue performance is another important quality of Hardide coatings for gas and steam turbine blades. Some other hard coatings introduce significant fatigue debit reducing the loads or life of the coated blades by as much as 60%. Hardide-A coating shows minimal fatigue debit between +10% and -10% in both rotating bend and axial high cycle fatigue tests.

COATINGS FOR GAS TURBINES

The Hardide-A coating reduces the wear, corrosion and erosion of gas turbine blades, maintaining high efficiency for longer and reducing significant ongoing maintenance costs.

Hardide-coated blades are currently installed in advanced gas turbine engines for Ansaldo Energia, enabling high operational flexibility and cutting CO2 emissions and operational costs, and are in test with other large manufacturers of IGTs.

COATINGS FOR STEAM TURBINES

Hardide coatings extend the life of steam turbine blades through significantly enhanced resistance to WDE and solid particle erosion.

Water condensate droplets can accumulate on stationary turbine vane surfaces, forming larger droplets which can impact the leading edges of rotating blades, causing WDE towards the last rows of the turbine. Hardide coatings protect the leading and trailing edges of the blades which increases their service life, maintaining optimal turbine efficiency for longer, saving downtime and maintenance costs. Solid particle erosion testing of Hardide-coated blades carried out at the University of Manchester on behalf of EDF Energy proved that the Hardide CVD coating provides a significant improvement for preventing material loss rates.