The influence of boron on the grain boundary chemistry and microstructure of ni- 16cr- 9fe- 0.03c

Autor:	Gary S. Was, R. M. Kruger
Rok vydání:	1988
Předmět:	Yield (engineering) Materials science Precipitation (chemistry) Metallurgy Metals and Alloys chemistry.chemical_element Intergranular corrosion Condensed Matter Physics Microstructure Grain growth chemistry Mechanics of Materials Grain boundary diffusion coefficient Grain boundary Boron
Zdroj:	Metallurgical Transactions A. 19:2555-2566
ISSN:	2379-0180 0360-2133
DOI:	10.1007/bf02645483
Popis:	High-purity Ni-16Cr-9Fe-0.03C was doped with 50 wppm B in order to determine the effects of B on the grain boundary chemistry and microstructure following both high temperature anneals (1373 to 1473 K) and lower temperature heat treatments (873 to 973 K). The anneals at high temperature yield precipitate-free grain boundaries in the B-free material, while the addition of B results in the intergranular precipitation of B-containing M7X3 and M23X6 and a 30 to 50 Pct reduction in grain growth. The low temperature heat treatments of the B-free material result in the growth of intergranular Cr-rich M7C3, which in turn causes Cr depletion at the grain boundary. Adding B does not affect the Cr concentration at the grain boundary nor the width of the Cr-depleted zone. However, B segregation occurs, with a segregation energy of 42.6 kJ/mole. In addition, intergranular Ni + B-rich M23X6 forms. These changes in the grain boundary chemistry due to B cause a reduction in intergranular attack of up to 50 Pct as measured by the electrochemical potentiokinetic reactivation test in a solution of 0.05 M H2SO4 + 0.05 M KSCN.
Databáze:	OpenAIRE
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