AN ELECTRON-METALLOGRAPHIC STUDY OF EMBRITTLEMENT IN AN 18NI-8CO-MO MARAGING STEEL.
UNITED STATES STEEL CORP PITTSBURGH PA
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Recent information has indicated that 18Ni-8Co-Mo type maraging steels can be embrittled by holding at 1400 F during the solution annealing treatment. Thus, heavy maraging-steel plates 2 in. thick and over may be embrittled during solution annealing because they would cool slowly at temperatures in the vicinity of 1400 F. Because steel plates up to 4 in. thick are required for submarine-hull weldments, this embrittling tendency might severely limit the use of maraging steels in this application. Therefore, a metallographic study was initiated to determine the cause of the embrittlement in specimens of a 250ksi maraging steel submitted by INCO. Lightmicroscopy, electron-microscopy, X-ray-diffraction, electron-diffraction, and microprobe techniques were used in the investigation. Author