Effects of alloy 718 microstructure on hydrogen embrittlement susceptibility for oil and gas environments

Abstract

The effects of alloy 718 microstructure on hydrogen embrittlement susceptibility and tensile fracture mode were assessed through slow strain rate tensile testing and fracture surface analysis. Alloy 718 was annealed and aged to produce microstructures with variations in grain size and amount of grain boundary precipitates. Furthermore, the different ageing conditions likely resulted in differences in volume fractions and sizes of γ′ and γ′′ precipitates. The extent of grain boundary precipitation had the strongest effect on hydrogen embrittlement susceptibility, while grain size did not have any significant effect. Hydrogen embrittlement susceptibility was also correlated with differences in strength level, which was primarily controlled by the γ′ and γ′′ precipitate populations.

Effect of Microstructure and Alloy Chemistry on Hydrogen Embrittlement of Precipitation-Hardened Ni-Based Alloys

“…Hence, both alloys, with their various microstructure variants, exhibit a relationship between strength and HE, which is in agreement with previous works [11,21] .…”

Slow Strain Rate Testing for Hydrogen Embrittlement Susceptibility of Alloy 718 in Substitute Ocean Water

“…As a result, due to the limited ingress of hydrogen, the UPC specimens charged in situ in SOW exhibited only a small amount of embrittlement. This result agrees with previous studies on Alloy 718 where the charging electrolyte was a 3.5% NaCl solution (Ref 33) but disagrees with previous studies where H 2 SO 4 was used as the charging electrolyte ( Ref 25,29,30). While the hydrogen fugacity is affected by many factors such as applied potential, temperature, surface deposits, and recombinant poisons, it would be expected that, under reasonably similar conditions, H 2 SO 4 would produce a higher fugacity than SOW.…”

A critical appraisal of laser peening and its impact on hydrogen embrittlement of titanium alloys

“…Typical mechanical ways of failures include corrosion, buckling, microfouling, 104 fracture, fatigue, creep, fatigue, thermal shock yielding, HE, aqueous stress corrosion 105,106 and mechanical overload. Advanced materials like Titanium and Inconel alloys 107,108 can challenge almost all these failures other than HE; the reason is that hydrogen diffusion can occur at elevated temperatures and even at relatively lower temperatures. Hydrogen damage can be done in three types: solid solution hardening, the internal defects creation and HE.…”