High-temperature processes in the defence/armaments industry

The manufacture of defence goods places the highest demands on metallurgical processes. Armour steel alloys, high-performance materials for engines and ballistically optimised materials are produced in melting, casting and heat treatment processes that require temperatures in excess of 1,600 °C. Refractory linings in electric arc furnaces, induction furnaces and vacuum furnaces must therefore be highly resistant not only thermally but also chemically — aggressive slags and special alloys attack conventional refractory materials considerably more severely than in civil steel production.

• Armour steel and ballistic protection steel: melting and casting at over 1,650 °C in electric arc furnaces with a basic refractory lining
• Engine alloys (nickel-based): vacuum induction melting (VIM) with alumina or magnesia crucibles
• Heat treatment: continuous furnaces and chamber furnaces for quenching and tempering, hardening and stress-relief annealing of safety-critical components
• Additive manufacturing: the atomisation of metal powders for 3D printing requires high-purity melting processes with special crucible linings
• Ammunition production: casting processes for projectile casings and penetrators with defined microstructures

Thermal protection is a technology field in its own right within the defence industry. From heat shields in missiles and exhaust systems in armoured vehicles through to thermal insulation in marine propulsion systems — refractory materials are used wherever temperatures exceed the capability of conventional materials. The requirements go far beyond static furnace linings: thermal shock resistance, low weight and resistance to vibration and acceleration are decisive selection criteria.

• Missiles and re-entry vehicles: ablative heat protection materials based on carbon fibre and ceramic composites
• Exhaust systems of armoured vehicles: refractory linings must withstand temperatures of over 900 °C while simultaneously being subject to vibration loads
• Ship propulsion: gas turbine combustion chambers and exhaust paths in frigates and corvettes require high-temperature-resistant insulating materials
• Rocket motors: nozzle throat linings made of graphite, tungsten or ceramic matrix composites (CMC)

Modern weapon systems and platforms depend on high-performance energy systems. Gas turbines in main battle tanks, ship propulsion systems and auxiliary power units in aircraft generate extreme temperatures that call for refractory linings, combustion chamber materials and thermal barriers. The move towards directed energy weapons (DEW) and hypersonic technologies is intensifying the demands on thermal management still further.

• Gas turbines (MTU, Rolls-Royce): thermal barrier coatings (TBC) based on yttria-stabilised zirconia protect turbine blades at over 1,300 °C
• Directed energy weapons: cooling systems and thermal shielding for high-energy lasers require materials with extremely low thermal conductivity
• Hypersonic technology: nose caps and leading-edge materials must withstand temperatures of over 2,000 °C while simultaneously subject to aerodynamic loads
• Field camp power supply: mobile combustion systems and waste heat recovery with refractory lining

Refractory materials in a defence context are subject to stricter testing and documentation requirements than in civil industry. Quality assurance covers not only materials testing (compressive strength, porosity, thermal conductivity) but also complete traceability of the raw materials, batch release by the client and compliance with military specifications.

• First Article Inspection (FAI): initial sample inspection to AS9102 for every new refractory product in a defence context
• Batch tracking: complete documentation from the raw material through to the installed refractory material — compliant with AQAP 2110
• Non-destructive testing (NDT): ultrasound, radiography and thermography to assess lining integrity in the installed condition
• Environmental simulation: thermal cycling, vibration testing and corrosion resistance under simulated operational conditions

The defence industry is investing heavily in future technologies, all of which require high-temperature processes. From the Future Combat Air System (FCAS) and hypersonic missiles through to new armour concepts — the demands on refractory technology and thermal management will continue to rise. This opens up long-term business opportunities for specialised suppliers.

• FCAS/NGWS: the next generation of engine materials for stealth requirements and higher operating temperatures
• Additive manufacturing: 3D printing of refractory components for prototypes and very small batches — shortening development cycles from years to months
• Ceramic matrix composites (CMC): lighter than metal, more temperature-resistant — a paradigm shift in engine technology
• Rare earth recycling: high-temperature processes for recovering strategic raw materials from decommissioned weapon systems