The susceptibility of precipitation hardening 13-8 Mo stainless steel to hydrogen embrittlement (HE) was measured by both post hydrogen charging tensile tests and by time to failure tests while being subjected to hydrogen charging and a static stress below the yield stress. In the former, it was found that the ductility was decreased substantially after only 30 min charging time. The strength was markedly reduced after 2 h charging time. In the delayed failure tests, it was found that a localized cold worked surface condition promoted crack formation.

No abstract

No abstract

In liquid or gaseous media, certain additives, called inhibitors, can occupy, via a strong binding energy to the base metal, atom sites on the metal surfaces, thus preventing a metal-hydrogen bond and thereby inhibiting the entry of hydrogen into the base metal. For both metallic and nonmetallic solid films, hydrogen entry can be prevented or reduced if the film has a lesser binding energy for hydrogen than the base metal and if a low solubility and/or a low diffusivity for hydrogen. Nonmetallic films appear to be the better films for preventing hydrogen entry and subsequent embrittlement of the base metal. Data are presented for oxide and nitride films in the 50 to 3000-nm range of thickness. A 50-nm-thick film of sputtered alumina (A12O3) and a 3000-nm-thick, thermally grown oxide film appear to prevent hydrogen embrittlement in the precipitation-hardening stainless steels.

A study has been made of the grain-boundary behavior in bi-crystals of sodium chloride and magnesia held under load at elevated temperatures. Grain-boundary sliding was observed in both materials, of a form similar to that found in metals. The sliding occurred not smoothly, but in discreet jumps followed by periods of zero movement. In sodium chloride the over-all sliding rate was found to depend upon four variables examined: stress, temperature, atmosphere, and boundary misorientation. Two variables examined, stress and boundary misorientation, were found to influence the over-all boundary sliding rate in magnesia. Void formation as a result of sliding was observed in a sodium chloride sample which contained a well-defined jog in its boundary. Implications that the present results bring to bear upon general considerations of the high temperature deformation and fracture behavior of polycrystalline nonmetallic materials are discussed.