Coarsening of Laves phase and creep behaviour of a Re-containing 10% Cr-3% Co-3% W steel

Published on Apr 22, 2021in Materials Science and Engineering A-structural Materials Properties Microstructure and Processing4.652
· DOI :10.1016/J.MSEA.2021.141137
Alexandra Fedoseeva10
Estimated H-index: 10
,
I. Nikitin5
Estimated H-index: 5
+ 1 AuthorsRustam Kaibyshev58
Estimated H-index: 58
Sources
Abstract
Abstract The coarsening of Laves phase in a Re-containing 10% Cr-3% Co-3% W steel during both creep and ageing at 923 K was investigated. The depletion of W solutes from the ferrite matrix is accompanied with the precipitation of Laves phase, wherein creep strain accelerates both these processes. The equilibrium W content in the ferritic matrix of 1.24 wt% and the volume fraction of Laves phase of 1.6% is reached after 500 h of creep and 1000 h of ageing. This is related to lower activation energy for W diffusion upon creep testing. The coarsening of Laves phase obeys Ostwald ripening and can be described in terms of Lifshitz-Slyozov-Wagner theory: d4 – d04 = Kp(t-t0), where Kp = 3.70–3.80 × 10−11 μm4 s−1 for both creep and ageing suggesting that the coarsening of these particles should be controlled by grain boundary diffusion. No strain-induced coarsening of Laves phase is observed. Growth of the Laves phase particles located on the lath boundaries and the high-angle boundaries of the blocks, packets and prior austenite grains occurs in independent manner. The Laves phase particles located on the high-angle boundaries are susceptible to coarsening that leads to appearance of the particles with dimensions >200 nm. The Laves phase particles located on the lath boundaries dissolve with a low rate. Dense chains of Laves phase on the lath boundaries retain up to high creep time giving a significant contribution to creep behaviour.
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