Impact fracture of embrittled stainless steels

Hydrogen embrittlement of austenitic stainless steels and temper embrittlement of a martensitic stainless steel have been studied by impact testing, metallography, and SEM fractography. New data for uncharged and hydrogen-charged specimens of Types 304L and 316L austenitic stainless steels show significant hydrogen effects on the impact behavior of both materials. The Type 316L specimens showed greater hydrogen effects and a more pronounced"ductile-to-brittle transition." Analysis of new and existing data for austenitic stainless steels suggests that a steel's susceptibility to hydrogen may be estimated on the basis of the magnitude of its ductile-to-brittle transition. Due to the roles played by slip planarity, transformation to martensite, and other strain rate sensitive factors, strict ordering of various steels' susceptibilities to hydrogen cannot be expected by this method. Nevertheless, the method may provide a reasonable alternative to thorough characterization of the effect of hydrogen on the mechanical properties of a given material. The Type 416 martensitic stainless steel specimens possessed a banded ferrite/tempered martensite microstructure. Non-embrittled specimens exhibited a microvoid coalescence mode of fracture. The temper embrittlement mechanism promoted transgranular fracture of the tempered martensite phase. In the banded microstructure, ferrite/ferrite and ferrite/tempered martensite interfaces were extraordinarily weak. Their failure early in the deformation process promoted ductility by permitting relaxation of constraint on the tempered martensite phase. Tempering condition, impact data, and hardness data were correlated in order to specify a maximum acceptable hardness for a given minimum service temperature.

Name thesis:degree_name

M.S.

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Materials Engineering

Department dc:contributor.department

Materials Engineering

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1986

Author dc:creator

• Rohr, Kathleen L.

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/91149

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/91149