Embrittlement of a High and a Low Strength Steel in Liquid Lead Environment

摘要

A study has been made of the cyclic fatigue fracture behavior of single-edge notched specimens of 4340 type high strength (yield stress 160 Ksi) and alloy steel of low strength (yield stress 100 Ksi) with and without a fatigue precrack tested in liquid lead and argon at 700 F. The high strength steel specimens were severely embrittled by liquid lead with stress intensity at fracture some two orders of magnitude lower in liquid lead than in the argon environment. The embrittlement susceptibility was the same for both the notched specimens and for the specimens that had a fatigue precrack at the root of the notch. On the other hand, identical as-notched specimens of low strength steel were immune to lead embrittlement. However, when these specimens were fatigue precracked, they were severely embrittled by liquid lead. This variation is susceptibility to embrittlement is discussed in terms of the prevalent reduction in cohesion mechanism of liquid metal embrittlement. The implications of these results in determining the embrittlement susceptibility or elimination are also discussed.