ISRO Successfully Tests Indigenous Nozzle Made of Stellite

In April 2025, ISRO successfully conducted a hot test of an indigenously developed nozzle divergent made of Stellite at the ISRO Propulsion Complex, Mahendragiri, Tamil Nadu, replacing the imported Columbium previously used in the PSLV's fourth stage.

Key Points

Self-Reliance Milestone: The nozzle divergent, previously made of imported Columbium, is now developed using Stellite — a cobalt-based alloy with Chromium, Nickel, Tungsten, and Iron.
High-Temperature Strength: Tests confirmed the Stellite component can withstand temperatures up to 1150°C.
Cost Efficiency: The switch to Stellite is expected to reduce material costs by 90%.
Successful Testing: After three prior tests, a final hot test lasting 665 seconds proved its reliability.
Gaganyaan Update: The same ISRO facility also successfully hot-tested the human-rated Vikas Engine, to be used in the LVM3 G launch vehicle for the Gaganyaan mission.
Vikas Engine: Designed and developed in India, the engine is named after Vikram Sarabhai and will power India’s crewed space missions.