Effect of Hydrogen Charging on Ambient and Cryogenic Mechanical Properties of a Precipitate-Strengthened Austenitic Steel
The method of high-pressure hydrogen charging was used to charge hydrogen into smooth and notched tensile specimens of γ′ precipitate-strengthened austenitic steel JBK-75. The hydrogen content in the charged specimens was 25.2 ppm (by weight). In the test temperature range 293 to 77 K, hydrogen had no obvious effect on strength, but it caused some decrease in ductility at 223 to 295 K. The steel is not notch sensitive, and hydrogen charging had little effect on notch sensitivity at ambient and low temperatures. With decreasing temperature, both strength and ductility increased, and hydrogen damage greatly decreased. Increasing the aging temperature and time tends to increase the hydrogen damage of the steel, but hydrogen had less effect on aged strength. The steel that had been given an appropriate heat treatment had excellent cryogenic mechanical properties and resistance to hydrogen damage. The steel had very stable microstructure at low temperatures; no phase transition occurred as a result of strain and hydrogen at 293 to 77 K. Fine grain and fine γ′ precipitates decreased hydrogen damage; the presence of ŋ phase at grain boundaries increased hydrogen damage.
KeywordsTensile Specimen Aging Temperature Hydrogen Embrittlement Cryogenic Temperature Hydrogen Charge
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