STRESS CORROSION CRACKING SUSCEPTIBILITY OF ALUMINUM-SILICON-BRONZE

摘要

A laboratory program was initiated to study the stress corrosion cracking susceptibility of aluminum-silicon-bronze (copper alloy C64210) valves used in gaseous fluorine (F_2) service. Some testing was also performed with 303 SS (UNS S30300) valves. The threaded outlet connections of the valves were torqued to different values and wetted with 3 wt percent hydrofluoric acid (HF) (to simulate a small F_2 leak), 5 percent potassium iodide (KI), or commercial leak detection solution. Branched, intergranular cracks initiated in all the test environments at the highly stressed thread root areas indicating that crack initiation was primarily dependent on the torque applied to the outlet connection. The aluminum-silicon-bronze material also experienced dealloying corrosion upon exposure to the hydrofluoric acid and potassium iodide solutions. The compatibility of the alloys in fluorine service is discussed.