Stress Corrosion Cracking of High Strength Steel Fasteners for Space Applications
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Cadmium electrodeposited Afnor 35NCD16 steel fasteners in hardened and tempered condition are used in the Indian space program. Failures were observed in size M6X17L fasteners that were under assembly load for a period of four months in an integrated test set up which involved exposure to severe humid environments. During disassembly, few of the fasteners were found to be broken at head–shank junction. Detailed metallurgical investigations carried out on failed fasteners and those, which were in assembly but did not fail, revealed their failure was caused by the synergistic effects of stress and corrosion. An attempt is made in this case history to correlate the metallurgical features collected with the failure mode of the fasteners.
KeywordsStress corrosion cracking Afnor 35NCD16 steel Failure analysis
The authors are indebted to Shri P.S. Veeraraghavan, Director, VSSC for permission to publish this work.
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