SOURCE: RAUNAK KUNDE / NEWS BEAT / IDRW.ORG
In a significant advancement for India’s aerospace and defence capabilities, the Defence Research and Development Organisation (DRDO) has successfully developed and manufactured high-pressure turbine blades (HPTBs) for a small indigenous turbo-fan engine, marking a crucial step towards self-reliance in critical aero engine components.
Published in the Defence Science Journal (Vol. 73, No. 2, March 2023), the study titled “Realization of High Pressure Turbine Blades of a Small Turbo-Fan Engine through Investment Casting Process” details the intricate process behind the creation of aeronautical-grade HPTBs by scientists from DRDO’s Defence Metallurgical Research Laboratory (DMRL), Hyderabad, and Gas Turbine Research Establishment (GTRE), Bengaluru.
The high-pressure turbine section is one of the most critical components in a gas turbine engine, responsible for extracting energy from high-temperature, high-pressure gases. The development was targeted for a twin-spool small turbo-fan engine (STFE) intended for unmanned aerial vehicles (UAVs).
Each turbine comprises 50 solid, unshrouded blades made of Ni-base superalloys, designed to withstand extreme mechanical stress, corrosion, and temperatures above 1,000°C. These blades were developed using vacuum investment casting, a process typically used for high-performance aero-engine components.
Process Highlights: Advanced Techniques and Precision Manufacturing
? Design and Tooling
The blade features a twisted aerofoil geometry, with extremely tight tolerances (±0.13 mm on the aerofoil contour).
A wax pattern die was designed with hinge-type construction to prevent breakage and to account for anisotropic shrinkage during casting.
CAD modeling and injection simulation software like Moldex3D® were used to optimize the die design and wax flow characteristics.
? Shell Mould Fabrication
The ceramic shell was built layer-by-layer using zircon fillers and colloidal silica binders, followed by stuccoing with mullite grits.
Moulds were preheated to 1190°C and then used to cast the blades with molten metal at 1540°C under vacuum conditions (1×10?³ Torr).
? Casting Evaluation
Over 1,700 castings were produced with a final yield of 74%, considered excellent for aeronautical-grade components.
Non-destructive evaluation (visual, FPI, and radiography) ensured that only defect-free blades were accepted.
Material & Performance Validation
? Microstructure & Porosity
Microscopy confirmed fine-grained, equiaxed structures with ?–?? phases, ideal for high-temperature strength.
Porosity levels were kept within strict limits: <1% in the aerofoil region and <2% in root/platform areas.
? Mechanical Properties
Heat-treated test bars met and exceeded required specifications:
Tensile Strength @ RT: 830 MPa (Min. required: 800 MPa)
Stress Rupture Life: Up to 88.7 hours at 975°C/196 MPa
Hardness: ~363 VHN after aging
Strategic Impact: Strengthening Aero Engine Self-Reliance
This achievement showcases DRDO’s growing capabilities in aero engine component development, particularly in mastering the complex casting of nickel-based superalloys, a domain long dominated by a few foreign OEMs.
As India advances its indigenous fighter jet programs like the Tejas Mk2, TEDBF, and the upcoming AMCA, the capability to manufacture such critical hot-section components domestically is a strategic necessity.
This success in HPTB manufacturing not only supports UAV propulsion but also lays the groundwork for broader indigenization of jet engine technology, which has historically been a bottleneck in India’s aerospace ambitions.
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