Some aspects of the occurrence of boron in alloy steels
1977; Taylor & Francis; Volume: 11; Issue: 7 Linguagem: Inglês
10.1179/msc.1977.11.7.225
ISSN2057-7834
Autores Tópico(s)High Temperature Alloys and Creep
ResumoHigh-resolution boron autoradiography and a literature survey have enabled an assessment to be made of the location of the small amounts of boron (0.002–0.005%) added to alloy steels. It has been shown that boron readily segregates to fcc carbides to give boro-carbides such as M23(BC)6 and V4(BC)3, and that metal borides are not formed in steels with this level of boron addition. Boron also segregates to austenite grain boundaries on slow cooling low-alloy steels below 980°C. Grain-boundary segregation thus occurs in ½%Mo–B bainitic steels as predicted by some harden ability theories. However, quenched and tempered Cr-Mo-V creep-resisting steels do not have boron at the austenite boundaries and the boron does not segregate to the boundaries even after creep testing for > 16 000 h at 550°C. The observed microstructural effects have been related to mechanical properties and interpreted in terms of vacancy–boron interactions.
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