Hybrid Silicide-Based Lightweight Components for Turbine and Energy Applications
Though remarkable high temperature ('HT') mechanical properties have been achieved (strength, creep), especially in the FP6 ULTMAT project, short/medium term application cannot be envisaged. This is because improved oxidation resistance and optimised micro structures for enhanced mechanical properties are required.
Nb/Nb5Si3 and Si3N4/MoSi2 composites are lightweight high temperature materials (with a density lower than about 6.5~7 g/cm3 and < 5.6 g/cm3, respectively) with application potential above 1300°C making them candidates for advanced aero-engine components, allowing reduction of fuel consumption, CO2 emissions and cooling air needs, hence a further increase in efficiency and reduction in engine weight.
The goal of the HYSOP project is to develop solutions for manufacturing lightweight high temperature turbine components and to design new coating systems (protection against oxidation, water vapour and CMAS).
The partners (engine manufacturer, research centres, universities) will join their expertise to reach following objectives:
- design static (vane, seal segment) and rotating (blade) components with tailored micro structures and properties, including super alloy/HT-material hybrid structures where superior performance is foreseen over monolithic material;
- develop the corresponding advanced routes for processing (based on powder metallurgy: net-shape HIPing, powder injection moulding, laser fabrication) and joining;
- design oxidation/corrosion resistant coating systems, based on expertise gained on substrate/coating/environment interactions on Nb-Si materials, super alloys and Environmental/Thermal Barrier Coatings;
- test the coatings in service-like conditions: medium (~800°C) and high (1100-1300°C) temperatures in dry/wet air, corrosion by molten oxides, up to a burner rig test;
- converge the two approaches in assessing the mechanical behaviour of bare and coated specimens;
- finally, to propose a set of manufacturing and coating solutions for the HT materials for medium term application in aero- and small land-based turbines.
Superalloys equal stronger, greener turbines
Researchers are developing lightweight components for turbines along with tougher coating systems. Combining these innovations improves the efficiency and reliability of large-scale industrial structures.
Turbines are used in aerospace engines, energy plants and other industrial installations. In these large-scale applications, lowering the weight of components brings big gains in terms of energy efficiency. However, they also have to be resistant to extremes of temperature, moisture and force.
Researchers are designing hybrid silicide-based structures that can meet the demand for lower-weight components without sacrificing durability. Working together through the EU-funded 'Hybrid silicide-based lightweight components for turbine and energy applications' (HYSOP) project, the international team is looking into making components with tailored microstructures and properties.
The composite materials they are focusing on — Nb/Nb5Si3 and SiN4/MoSi2 — are able to operate at above 1 300 degrees Celsius and show amazingly high strength. But the challenge is to develop coatings that can improve their oxidation resistance. The team has been testing various coating systems under high temperatures and environmental conditions.
Drawn from science institutes and industry from around Europe, the researchers are developing innovative manufacturing systems based on powder milling techniques, net-shape Hot Isostatic Pressing (HIP), powder injection moulding and laser fabrication.
Two conflicting trends mean significant improvements in energy efficiency are a must — the global demand for energy is ever-increasing, whilst the potential for catastrophic climate change calls for dramatic cuts in carbon dioxide (CO2) emission. These cutting-edge materials stand to be an integral part of the solution.