TY - JOUR
T1 - On the nucleation and dissolution process of Z-phase Cr(V,Nb)N in martensitic 12%Cr steels
AU - Danielsen, Hilmar Kjartansson
AU - Hald, John
PY - 2009
Y1 - 2009
N2 - Precipitation of large Z-phase particles, Cr(V,Nb)N, replacing fine MX nitrides, (V,Nb)N, has recently been
identified as a major cause of premature breakdown in long-term creep strength of a number of new 9–12%Cr martensitic steels. The Z-phase precipitates slowly during long-term exposure at around 650 ◦C accelerated by high Cr content in the steels. It appears that the nucleation process controls the precipitation rate of Z-phase. A 12%Cr steel, which had precipitated Z-phase during long-term operation at 660 ◦C/12,000 h, was further heat treated in order to investigate the dissolution and reappearance processes for the Z-phase. In both cases it appears that Z-phase and MXphase are in physical contact and have a preferred crystallographic orientation relationship. The proposed nucleation mechanism is a chromium diffusion controlled transformation of MX into Z-phase, which explains the rather low precipitation rate of Z-phase.
AB - Precipitation of large Z-phase particles, Cr(V,Nb)N, replacing fine MX nitrides, (V,Nb)N, has recently been
identified as a major cause of premature breakdown in long-term creep strength of a number of new 9–12%Cr martensitic steels. The Z-phase precipitates slowly during long-term exposure at around 650 ◦C accelerated by high Cr content in the steels. It appears that the nucleation process controls the precipitation rate of Z-phase. A 12%Cr steel, which had precipitated Z-phase during long-term operation at 660 ◦C/12,000 h, was further heat treated in order to investigate the dissolution and reappearance processes for the Z-phase. In both cases it appears that Z-phase and MXphase are in physical contact and have a preferred crystallographic orientation relationship. The proposed nucleation mechanism is a chromium diffusion controlled transformation of MX into Z-phase, which explains the rather low precipitation rate of Z-phase.
KW - Nucleation
KW - Z-phase
KW - 9-12%Cr steels
U2 - 10.1016/j.msea.2008.11.019
DO - 10.1016/j.msea.2008.11.019
M3 - Journal article
VL - 505
SP - 169
EP - 177
JO - Materials Science and Engineering: A - Structural Materials: Properties, Microstructure and Processing
JF - Materials Science and Engineering: A - Structural Materials: Properties, Microstructure and Processing
SN - 0921-5093
IS - 1-2
ER -