ISRO Embraces Heat and Corrosion-Resistant Stellite Alloy for PSLV Nozzle, Boosting Domestic Manufacturing
In a move supporting India’s self-reliance goals and aiming to lower rocket production expenses, the Indian Space Research Organisation (ISRO) announced its decision to utilize Stellite for manufacturing the nozzle of its Polar Satellite Launch Vehicle (PSLV) rocket.
Previously, ISRO relied on imported Columbium (C103) material for the nozzle of the PSLV’s fourth liquid-fueled stage. Seeking a domestic alternative in line with the “Make-In-India” initiative championed by Prime Minister Narendra Modi’s government, ISRO identified and tested Stellite (specifically KC20WN).
Stellite, described by ISRO as a cobalt-based alloy containing Chromium, Nickel, Tungsten, and Iron, is known for maintaining significant strength even at high temperatures, making it well-suited for demanding thermal environments.
The successful qualification followed rigorous testing. After an initial phase involving three hot tests on two separate hardware units, a final qualification hot test was conducted on April 8, 2025. This crucial test ran for 665 seconds at the ISRO Propulsion Complex in Mahendragiri, Tamil Nadu.
ISRO reports that switching to this domestically sourced alloy yields substantial cost benefits, estimating savings of around 90% for this specific component.
The suitability of Stellite for such applications was affirmed by Dr. Dheepa Srinivasan, Dean of Research and Innovation at MS Ramaiah University of Applied Sciences, Bengaluru.
Drawing on over 25 years of experience with high-temperature materials, she noted that Stellite alloys are renowned for their exceptional resistance to high-temperature oxidation, corrosion, and thermal fatigue.
Dr. Srinivasan highlighted their established use in demanding parts like nozzles, vanes, and combustion liners in engines and turbines, crediting their durability, wear resistance (due to hardness), and thermal stability.
This material substitution is another example of ISRO’s push indigenization.
Previously, the agency successfully developed its own atomic clocks for use in navigation satellites, replacing imported units (some of which had failed) and saving approximately ₹3 crore (around $351,000) per satellite, each carrying three such clocks.
