Inconel 718 Forging for Indian Aerospace: GTRE Kaveri, HAL Engine Division, and ISRO

August 12, 2026


India’s aerospace and space sector — HAL’s Aero Engine Division (Bengaluru), ISRO, and DRDO’s aeronautical laboratories consumes Inconel 718 forged compressor disc, turbine disc, and structural ring components for military aeroengines, launch vehicle propulsion systems, and missile propulsion. The GTRE (Gas Turbine Research Establishment, Bengaluru) developing the Kaveri engine, ISRO’s Vikas liquid propulsion engine (for GSLV/PSLV), and DRDO’s missile propulsion programmes all require Inconel 718 forging capability that has historically been imported or produced at government facilities. Make in India aerospace manufacturing creates the strategic imperative for domestic Inconel 718 forging supply from AS9100D-certified private sector Indian manufacturers.

Organisation / ProgrammeInconel 718 ApplicationSpecificationMake in India Status
GTRE — Kaveri engine (GTX-35VS)HP compressor disc, combustor casing ringAMS 5663 equivalent, CEMILACStrategic priority — domestic supply critical
HAL Engine Division (Bengaluru)Adour, Shakti, PTAE-7 engine componentsAMS 5663, AS9100DHAL vendor qualification required
ISRO — Vikas engine (GSLV/PSLV)Turbopump structural ring, combustion chamberISRO internal spec, AS9100DISRO qualified domestic vendor needed
DRDO — DRDL (Hyderabad)Missile propulsion structural ringsDRDO classified, AS9100D baselineAtmanirbhar Bharat — domestic priority
BDL — Akash missile propulsionSolid rocket motor casing structural fittingsDRDO specs, DGQAPIL listed — domestic mandatory

GTRE (Gas Turbine Research Establishment) — DRDO’s gas turbine R&D laboratory in Bengaluru — has been developing the Kaveri engine (GTX-35VS) for the Tejas LCA since the 1980s. While the Kaveri has faced development challenges, GTRE continues R&D on the engine core and is developing the Kaveri Derivative (KD) engine for unmanned combat aerial vehicle (UCAV) applications. The Kaveri’s high-pressure compressor uses Inconel 718 disc forgings processed to AMS 5663-equivalent specifications currently the most critical domestic Inconel 718 forging requirement in the Indian defence aerospace sector.

ISRO’s Vikas engine a liquid-fuelled rocket engine producing 790 kN thrust, used in the second stage of PSLV and the core stages of GSLV uses Inconel 718 for turbopump structural rings and injector plate structural components. The Vikas engine’s turbopump operates at very high rotational speeds (approximately 10,000 rpm) with liquid propellant Inconel 718’s combination of high strength, cryogenic toughness, and resistance to both reducing and oxidising environments makes it the design choice. ISRO has established its own material qualification process for domestic Inconel 718 forging suppliers.

HAL’s Engine Division (HAED, Bengaluru) produces the Shakti engine (a licensed Turbomeca Ardiden derivative for the Dhruv ALH helicopter) and the PTAE-7 (a Pratt & Whitney Canada JT15D derivative for the HJT-36 Sitara trainer). Both engines use Inconel 718 compressor and turbine structural rings. Private sector AS9100D manufacturers who receive HAED vendor approval can supply Inconel 718 structural rings for these programmes reducing HAED’s dependence on imported components and licensed OEM-controlled supply chains.

ISRO’s Gaganyaan human spaceflight programme — India’s first crewed orbital mission requires the highest levels of reliability and traceability for all structural components. The service module and crew module structural fittings and propulsion system hardware use Inconel 718 and Ti-6Al-4V forgings with the most stringent quality documentation requirements in Indian aerospace. ISRO’s vendor qualification for Gaganyaan-critical components includes witness testing, document audits, and independent third-party laboratory verification of material properties.

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Vinir Capability

  1. AS9100D full scope — the quality management baseline for CEMILAC, ISRO, and GTRE vendor qualification.
  2. Inconel 718 double ageing at 718°C ± 8°C and 621°C ± 8°C in AMS 2750-calibrated furnaces with full TUS records.
  3. AMS 5663-equivalent heat treatment with complete furnace documentation.
  4. VAR or triple-melt billet from Special Metals or Carpenter Technology for aerospace rotating component applications.
  5. AMS 2154 Class A immersion UT.
  6. FPI to AMS 2647.
  7. AS9102 FAIR capability for GTRE and HAED first article qualification.
  8. NABL chemistry (OES including trace elements) and mechanical testing.
  9. Ring rolling to Ø4,500mm for ISRO turbopump and DRDO missile structural ring applications.

Frequently Asked Questions

1. What is the Kaveri engine and why is domestic Inconel 718 forging supply critical to its development?+–
The Kaveri (GTX-35VS) is India’s domestically developed military gas turbine engine a 80 kN thrust class engine intended for the Tejas LCA. The high-pressure compressor discs which must withstand 600°C+ temperature, high centrifugal stress, and cyclic fatigue loading are manufactured in Inconel 718. Domestic supply of these Inconel 718 disc forgings from qualified Indian private sector manufacturers is a strategic requirement for the Kaveri programme import dependency for critical engine components creates supply chain vulnerability that the Atmanirbhar Bharat programme is specifically designed to eliminate.
2.What is ISRO’s vendor qualification process for Inconel 718 forging supply?+–
ISRO’s vendor qualification for critical structural forging supply involves: document assessment (AS9100D certificate, NABL accreditation scope, manufacturing process capability description), process qualification (production of qualification forgings in Inconel 718 with full documentation per ISRO’s internal material specification), independent testing (ISRO may send test specimens from the qualification lot to an independent laboratory for verification testing), and on-site assessment by ISRO’s Quality Assurance group. The qualification timeline for a new ISRO Inconel 718 forging vendor is typically 12–24 months.
3. What Gaganyaan human spaceflight programme structural forging requirements apply and why are they the most demanding in Indian aerospace?+–
Gaganyaa – India’s first crewed orbital mission carries three astronauts for a 3-day mission in low Earth orbit. Inconel 718 and Ti-6Al-4V structural forgings for Gaganyaan applications require: complete material traceability (heat number to finished component), independent third-party verification of all material properties (no reliance on supplier self-certification alone), witness testing by ISRO’s quality assurance team, and specific document retention requirements. Unlike satellite missions where a failed structural component results in mission loss, Gaganyaan structural forging failures could result in crew fatalities the consequence severity drives the most conservative quality requirements in ISRO’s programme portfolio.
4.What is the DRDO Positive Indigenisation List (PIL) for missile propulsion components and what forging categories does it cover?+–
DRDO and MoD have listed several missile propulsion and structural component categories on the Positive Indigenisation List after the specified date, these items can only be procured from Indian domestic manufacturers. For forging specifically, missile body section ring forgings (Ti-6Al-4V, Ø150–800mm), combustion chamber structural fittings (Inconel 718, Inconel 625), and solid rocket motor casing structural rings (D6AC or M300 maraging steel) are among the categories targeted for domestic supply. These are precisely the forging categories that an AS9100D-certified Indian ring rolling manufacturer with titanium and nickel alloy capability can supply.
5.How does HAL’s Engine Division vendor qualification work for private sector Inconel 718 forging suppliers?+–
HAED (HAL Aero Engine Division) qualification for private sector forging suppliers follows a structured process: initial capability assessment (AS9100D certificate, manufacturing process description, testing capability); technical audit by HAED’s Quality Assurance Group at the supplier’s facility; qualification lot production (typically 3–5 disc or ring forgings) with HAED QAG witness inspection of key operations (furnace loading, heat treatment, UT); material testing verification; and approval and listing as a HAED-approved forging vendor. The process takes 12–24 months. HAL’s Engine Division has an active vendor development programme private sector manufacturers can engage through HAL’s Vendor Development and Indigenisation cell.