Hydrogen-Induced Cracking Tests of High-Strength Steels and Nickel-Iron Base Alloys Using the Bolt-Loaded Specimen.
ARMY ARMAMENT RESEARCH DEVELOPMENT AND ENGINEERING CENTER WATERVLIET NY BENET LABS
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Hydrogen-induced cracking tests were conducted on high strength steels and nickel-iron base alloys using the constant displacement bolt-loaded compact specimen. The bolt-loaded specimen was subjected to both acid and electrochemical cell environments to produce hydrogen. The materials tested were A723. Maraging 200, PH 13-8 Mo. Alloy 718, Alloy 706, and A286, ranging in yield strength from 760-1400 MPa. The effects of chemical composition, refinement, heat treatment, and strength on hydrogen-induced crack growth rates and thresholds were examined. In general, all high strength steels tested exhibited similar crack growth rates and threshold levels. In comparison, the nickel-iron base alloys tested exhibited crack growth rates up to three orders of magnitude lower than the high strength steels tested. It is widely known that high strength steels and nickel base alloys exhibit different crack growth rates, in part, because of their different crystal cell structure. In the high strength steels tested, refinement and heat treatment had some effect on hydrogen-induced cracking, although strength was the predominant factor influencing susceptibility to cracking. When the yield strength of one of the high strength steels tested was increased moderately, from 1130 MPa to 1275 MPa, the incubation times decreased by over two orders of magnitude, the crack growth rates increased by an order of magnitude, and the threshold stress intensity was slightly lower.
- Properties of Metals and Alloys