Nickel-based superalloys

A single figure captures the stakes: nickel-based superalloys make up more than half the weight of an advanced aircraft engine. These are the materials that must hold their strength inside the hottest, most stressed part of a jet engine, where temperatures approach the melting point of the metal itself. Get them wrong and the engine does not fly. Until recently, India imported 70 to 80 per cent of its specialised aerospace alloys.

The difficulty is not incidental. A superalloy must resist creep, oxidation and fatigue at temperatures that would soften ordinary steel, and it must do so reliably across thousands of flight hours. Producing it demands vacuum induction melting and remelting to reach the required purity, near-isothermal forging to shape high-strength discs, and — for the most demanding turbine blades — single-crystal casting, in which a blade is grown as one continuous crystal to eliminate the grain boundaries where cracks begin. Only eight nations produce these alloys at aerospace grade: the United States, the United Kingdom, France, Germany, Russia, China, Japan and India. The global supply is concentrated in a handful of firms — Special Metals, ATI, Carpenter Technology and Haynes International in the US, Aubert & Duval in France, VDM Metals in Germany.

India's presence on that list rests largely on Mishra Dhatu Nigam Limited (MIDHANI), the Hyderabad public-sector metals producer. MIDHANI developed the strategic superalloys for the Kaveri engine programme entirely through in-house research. It supplies the titanium alloys, stainless steel, superalloys and nickel-based alloys used across Indian aircraft programmes, including the Tejas fighter.

The current effort centres on the 120 kN engine intended for the Advanced Medium Combat Aircraft (AMCA). As of 2025-2026, MIDHANI has completed material-level development for about 50 per cent of the total alloy systems the engine requires. Of those developed alloys, roughly 80 per cent have been certified by CEMILAC — the military airworthiness authority — for series production, covering mill forms and forgings of nickel-based superalloys. To support the next stage, MIDHANI has commissioned a 6,000-tonne near-isothermal forge press and revamped its vacuum induction melting furnaces to handle larger remelt stock and master heats for single-crystal superalloys.

That last phrase marks where the gap still sits. The status is best described as producing, not complete. Half the alloy systems for the AMCA engine remain undeveloped, and single-crystal casting — the process essential for the hottest-running turbine blades in a modern engine — is still emerging rather than established in India. The foundational processes beneath the material tell the same story: melting and forging capability is in production, but the single-crystal route, the hardest of the three, is the least mature.

The reason the gap persists is structural. A superalloy is not a single product but a family of dozens of specific compositions, each tuned to a location in the engine and each requiring its own development, testing and airworthiness certification before it can enter a flying engine. Certification is slow by design, because failure is not survivable. Building the physical plant — the presses, the vacuum furnaces, the remelting capacity — is a precondition, not the finish line; the alloys must then be qualified one by one.

What it would take is visible in the trajectory already under way: completing the remaining alloy systems for the 120 kN engine, maturing single-crystal casting from an emerging capability to a production one, and running each new composition through the full certification cycle. The equipment now being installed is sized for that work. The climb from half the alloys certified to a fully indigenous engine material set is the steep part — and India is on it.