Effect of cobalt on the microstructure of tempered martensitic 9Cr steel for ultra-supercritical power plants

Kinetics of Z-Phase Precipitation in 9 to 12 pct Cr Steels

“…Thus, the TTP diagrams in Figure 6 should represent 10 pct Cr and 13 pct Cr carbon-containing commercial grades. It must also be taken into account that newer experimental/commercial steels may also contain elements such as Co, which increases the precipitation speed of Z-phase, [15,16] and the current model alloys contains a relative large amount of nickel, which is considered to accelerate Z-phase precipitation speed. [17] Fig.…”

Prospects for Martensitic 12 % Cr Steels for Advanced Steam Power Plants

“…This is lost by Z-phase precipitation in the long-term range, whereby the creep strength is reduced. It has been found that contents of Ni and Co in 9-10%Cr steels accelerate the Z-phase transformation significantly [22][23][24]. The improved long-term performance of the BH steel compared to the MARBN steels could thus be caused by the reduced Co content of 1.8 wt.% as compared to the 3 wt.% in the MARBN steels.…”

Effect of Martensitizing Temperature on Creep Strength of Modified 9Cr Steel

“…This results in the delay of the onset of accelerating creep. Abe and his colleagues 6,21) studied the relation between time to rupture of a high Cr ferritic steel and percentage of occupation near prior austenitic grain boundaries by precipitates and proposed a similar explanation for creep strengthening of high Cr ferritic steel. It is reported that the size and shape of lath and block of martensite is fine for rapid cooling, because martensite deforms at the speed of sound.…”