Near-isothermal forging

Only seven nations can manufacture the high-pressure compressor discs at the heart of a modern jet engine. As of 2021, India became one of them.

Near-isothermal forging is the process behind those discs. The workpiece and the dies are heated to nearly the same high temperature and the metal is pressed slowly, so that difficult-to-deform titanium alloys flow into near-final shape without cracking. It is essential for the compressor discs in every modern fighter engine — components that must hold their strength above 600°C while spinning under enormous stress. The difficulty is that the alloys that survive those conditions are precisely the alloys that resist being shaped. Mastering the process demands vacuum furnaces to heat parts without oxidation, dies held to an exact temperature and geometry, and real-time control of temperature and deformation to produce the required microstructure.

India crossed the threshold in May 2021. The Defence Metallurgical Research Laboratory (DMRL) established the technology for all five stages of HPC discs using a 2,000 MT isothermal forge press. Working with Mishra Dhatu Nigam (MIDHANI), it produced 200 disc forgings and supplied them to HAL's Engine Division in Bengaluru. The discs met all airworthiness requirements, received type certification and a Letter of Technical Approval, and were cleared by the IAF for fitment into the Adour 804/811 and 871 engines that power Jaguar and Hawk aircraft. DMRL transferred the technology to MIDHANI through a licensing agreement so that bulk production could move beyond a laboratory. The methodology is generic, and can be tuned for other compressor components.

The gap is now one of scale, not of principle. DMRL's press is a research asset; MIDHANI operates a 6,000 MT press, the world's second-highest by that account. But those capacities fall short of the heavy, stress-tolerant components that next-generation engines demand, and India still depends on imported forgings for engines such as the Kaveri. The bottleneck sits above a foundation India already partly holds — the alloys, furnaces, dies, control systems and certification chain are all demonstrated or in production domestically. What is missing is press tonnage.

That is what the current effort addresses. In December 2025, HAL received four bids for a strategic 20,000-ton isothermal forging press facility, among them MIDHANI, Bharat Forge and PTC Industries — the last already supplying Safran and Dassault. A press of that size would place India among the select nations able to forge the largest engine components at home. The certified capability exists; the task is to build it big.