Accession Number : ADA133460

Title :   The Nature of Quasicleavage Fracture in Tempered 5.5 Ni Steel After Hydrogen Charging.

Descriptive Note : Technical rept.,

Corporate Author : CALIFORNIA UNIV BERKELEY DEPT OF MATERIALS SCIENCE AND MINERAL ENGINEERING

Personal Author(s) : Kim,Y H ; Morris,J W , Jr

PDF Url : ADA133460

Report Date : Oct 1982

Pagination or Media Count : 25

Abstract : Quenched and tempered 5.5Ni steel was embrittled by hydrogen charging and broken in air at room temperature. The primary fracture mode was transgranular quasicleavage. The quasicleavage facets were studied by scanning electron fractography and by transmission electron microscopy of profile fractographic specimens. The latter were prepared by plating the fracture surface with nickel and thinning so that the fracture surface was contained within the region of the specimen that was transparent to the electron beam. The fracture surface generally followed martensite lath boundaries. In addition, interlath microcracks were frequently found in the material immediately beneath the fracture surface. These results suggest that transgranular hydrogen embrittlement in this steel is primarily an interlath cracking phenomenon. Since the lath boundary planes tend to lie in (110), the results also explain the pervelance of (110) quasicleavage in the embrittled specimens, which contrasts with the (100) cleavage found in uncharged specimens broken below the ductile-to-brittle transition temperature.

Descriptors :   *Nickel steels, *Fracture(Mechanics), *Hydrogen embrittlement, Cleavage, Tempering, Microcracking, Martensite, Ductile brittle transition, Electron microscopy, Fractography

Subject Categories : Metallurgy and Metallography
      Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE