Physical and mechanical characteristics of EP741 and EP99 high-temperaturenickel alloys in high-pressure hydrogen gas

This paper presents research of the hydrogen gas effects on physical and me chanical properties of the precipitation-hardened nickel alloys EP741 and E P99 at pressures up to 65 MPa and temperatures up to 840 degrees C. It has been shown that conventional yield strength, tubular-shaped sample fracture stress and long-term strength are not practically affected by hydrogen. Th e characteristics of alloy ductility are more susceptible to hydrogen effec t. EP741 alloy Is especially susceptible to the hydrogen environment effect at temperature of 460 degrees C, and EP99-at temperatures of 20 degrees C and 460 degrees C. Hydrogen permeability relationships for alloys in a wide range of temperature and pressure were obtained. (C) 1999 International As sociation for Hydrogen Energy. Published by Elsevier Science Ltd. All right s reserved.