Metallic Thermal Insulation Material for Brake Piston Insulator of LCA
The Brake Piston Insulator is a critical component for wheel and brake assembly of Light Combat Aircraft (LCA). During the braking action of the aircraft, the piston insulator has to withstand high compressive loads and high temperatures. Therefore, the material for insulator must exhibit high compressive strength and low thermal conductivity for which sintered stainless steel with refractory additives is selected as the insulator material.
Technology Developed at DMRL
DMRL has indigenously developed a powder metallurgy based technology for producing the stainless steel based brake piston insulators. The process involves many steps such as selection of material, preparation of powder mixture with correct composition and uniform distribution, uniaxial compaction to get the desired green density, sintering in hydrogen atmosphere and machining/surface finishing. The laboratory has successfully optimized all processing parameters and also developed the necessary processing facilities such as ball milling system, uniaxial compaction in die and turning & grinding facilities.
The technology developed by DMRL has been type approved by Centre for Military Airworthiness & Certification (CEMILAC) after large number of taxi trials. Earlier the Russian made insulators were being used in LCA. The indigenous technology developed by DMRL will meet the country’s immediate requirements as well as make it fully self‐reliant in this area.
Typical Properties
The characterization includes density, hardness, compressive strength, surface roughness and thermal conductivity measurements. The typical properties of insulator material are given in the Table which have been found equivalent to the properties of imported insulator.
Density : > 5.3 g/cc
Hardness : > 105 BHN
Compressive Strength : > 320 MPa
Thermal conductivity : < 12 W/mK
Applications
The material developed can also be used in thermo‐mechanical applications where both thermal management as well as mechanical stresses are involved like nose cone of a missile, tiles of re‐entry vehicle, brake piston insulators in fighter plane, etc.