Tensile and impact properties changes of HASTELLOY X after exposure in high-temperature helium environment

Experimental results are presented on the changes in mechanical properties of HASTELLOY X* after being used in the liner tube of HENDEL hot gas duct under high temperature helium gas for about 6000 hours. In both room and elevated-temperature tensile tests, 0.2 pct proof stress and total elongation were significantly decreased after exposure in high temperature helium. Room-temperature impact toughness of the exposed specimens exhibited a much lower absorbed energy (about 5.0 × 10⁶ J/m²) than that of unexposed specimens (about 1.5 × 10⁶ J/m²). The fracture modes of tensile test specimens were more closely correlated with the test temperature than with the long-time exposure; however, long-time exposure is more affected by the tensile strength of HASTELLOY X than the test temperature. Moreover, “downstream effect” for the carbide precipitation reaction occurred in the liner tube of the HENDEL hot gas duct. HASTELLOY is a trademark of Cabot Corporation.