The effects of heat treatment and hydrogen on the SCC behavior of superalloy 718

Book · Tue Oct 01 04:00:00 EDT 1996

OSTI ID:367726

Wang, C P; Yu, G P; Huang, J H ^[1]

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1. National Tsing-Hua Univ., Hsinchu (Taiwan, Province of China). Dept. of Nuclear Engineering and Engineering Physics

The effects of heat treatment and cathodically hydrogen charging on susceptibility of nickel-based superalloy 718 to stress corrosion cracking were studied. Two conditions of solution-annealed (SA) and heat-treated (HT) materials were considered. Slow strain rate tensile tests with strain rates of 1 x 10{sup {minus}6} sec{sup {minus}1} were performed in 0.1M NaCl solution at room temperature on tensile specimens. Cathodic charging of hydrogen with the potential ranging from {minus}900 mV{sub SCE} to {minus}1,350 mV{sub SCE} were applied during SSRT tests. Reduction of area and ultimate tensile strength were used to correlate the relative susceptibility to different hydrogen charging conditions. Fractography of alloy 718 was usually transgranular, and there was a transition from dimpled microvoid coalescence to intergranular-like failure (transgranular failure adjacent to grain boundaries) as cathodic potential increased. Identification of grain boundary precipitates were carried out by the EDS technique on SEM and XRD of electrolytically extracted phases. MC carbides coalescence with microcracks acted as a preferred crack initiation and propagation site, and promoted crack tip deformation. The HT alloy 718 suffered more hydrogen damage than SA one because large amount of MC carbides precipitated in HT material.

• OSTI ID: 367726
• Report Number(s): CONF-960389--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CRACK PROPAGATION
EXPERIMENTAL DATA
FRACTURE PROPERTIES
HYDROGEN EMBRITTLEMENT
INCONEL 718
MECHANICAL TESTS
MICROSTRUCTURE
SCANNING ELECTRON MICROSCOPY
SODIUM CHLORIDES
STRESS CORROSION
ULTIMATE STRENGTH
X-RAY DIFFRACTION