Hydrogen-Induced Stress Corrosion Cracking Susceptibility Analysis of Pitch Links From the AH-64 Apache Helicopter.

摘要

AH-64 Apache helicopter pitch links were evaluated for degradation of mechanical properties due to service and susceptibility to hydrogen embrittlement. The pitch links were manufactured from 4340 electroslag remelted steel and heat treated to an HRC 52 hardness level and/or retempered to a HRC 38 hardness level and vacuum cadmium coated. Samples from fielded pitch links and virgin material were evaluated for comparison of mechanical behavior. Static torque-load tests on pitch links immersed in 3.5% NaCl at a potential of -1.2 V(SCE) were conducted for 1000 hours. Stress corrosion cracking resistance under hydrogen embrittlement conditions were determined. Mechanical and stress corrosion testing demonstrated no discernable change in properties due to service. Retempering the HRC 52 pitch links to HRC 38 resulted in properties similar to those expected from the 4340 ESR steel directly heat treated to the same hardness level. The immersion tests indicated no failure of the pitch links even at six times the service torque. The retempered material exhibited greater resistance to hydrogen-induced cracking.... Helicopters, Stress corrosion cracking (SCC), 4340 steels, Hydrogen embrittlement, Pitch links, Mechanical properties.