Effect of W on tempering behaviour of a 3 %Co modified P92 steel

The tempering behaviour of two 9Cr–3Co–0.5Mo–0.2 V–0.05Nb–0.005B steels containing 2 and 3 wt% W was examined. The decomposition of retained austenite induces the formation of semi-continuous films of W-rich M 23 C 6 carbides along boundaries at 525 °C. The increase in W content from 2 to 3 wt% modi...

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Bibliographic Details
Published in:Journal of materials science 2016-10, Vol.51 (20), p.9424-9439
Main Authors: Fedoseeva, A., Dudova, N., Glatzel, U., Kaibyshev, R.
Format: Article
Language:English
Subjects:
Austenite
Boundaries
Carbides
Carbon nitride
Carbonitrides
Characterization and Evaluation of Materials
Chemistry and Materials Science
Chromium molybdenum vanadium steels
Classical Mechanics
Crystallography and Scattering Methods
Dislocations
Dispersions
Ferritic stainless steels
Formations
Heat resistant steels
High strength steels
Laves phase
Materials Science
Original Paper
Phase separation
Polymer Sciences
Precipitation (Meteorology)
Retained austenite
Separation
Solid Mechanics
Steels
Tempering
Thermodynamics
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Summary:The tempering behaviour of two 9Cr–3Co–0.5Mo–0.2 V–0.05Nb–0.005B steels containing 2 and 3 wt% W was examined. The decomposition of retained austenite induces the formation of semi-continuous films of W-rich M 23 C 6 carbides along boundaries at 525 °C. The increase in W content from 2 to 3 wt% modifies the normal carbide precipitation sequence in the vicinity of these boundaries. The formation of W segregation at prior austenite grain/interlath boundaries leads to formation of the thermodynamically metastable W-rich M 6 C carbides. Finally, these M 6 C carbides transform to a stable Laves phase. Two-phase separation of MX carbonitrides into Nb-rich and V-rich dispersoids appears in both steels after tempering at 750 °C. This separation is thermodynamically metastable and attributed to the precipitation of Nb-rich MX carbonitrides with a round shape on dislocations at T  ≤ 450 °C and V-rich MX carbonitrides within ferritic matrix at 750 °C. Moreover, in the steel with 2 %W, the additional separation of V-rich MX carbonitrides into W-rich particles located in the vicinity of the prior austenite grain/lath boundaries and W-free ones located within the interiors of laths was observed.
ISSN:0022-2461
1573-4803
DOI:10.1007/s10853-016-0188-x