Coalesced martensite in pressure vessel steels

Hector Pous-Romero and H. K. D. H. Bhadeshia


An alloy commonly used for large pressure vessels, known as SA508 Gr. 3, has a microstructure after heat treatment consisting of a mixture of tempered bainite and martensite at fast cooled regions near surfaces subject to water quenching. These two phases are conventionally recognised to consist of fine platelets, each of which is approximately 0.2 μm in thickness; enhancing strength and leading to good toughness properties.

We have discovered in our experimental work that there are circumstances where the adjacent platelets of a similar orientation can coalesce as the austenite transforms, to produce much coarser structures which are believed to be detrimental to toughness. An examination of published micrographs reveals that such coalesced regions existed but were not noticed in previous studies. The mechanism of coalescence is described and methods to ameliorate the coarsening are discussed.

Journal of Pressure Vessel Technology 136 (2014) 031402.

Download paper

Download Archives of Related Unpublished Data
Dilatometric data Driving forces Latex and figures SEM images

coalesced martensite

Related papers

Anisotropy of pipes Abrasion of superbainite Non-cubic ferrite Computational metallurgy Theory for hydrogen
Cottrell issue Surface hydrogen Piping TiC precipitates Nb-rich pipe
TRIP welds Review, LTT welds MA constituent Microstructural entropy Multiple martensite

CML Home Materials Algorithms