Quantification of precipitates in a 10%Cr steel using TEM and EFTEM

Modern (9-12)%Cr steels designated for power plants with higher steam param eters show a pronounced time dependent change in microstructure during pure ly thermal or creep stress exposure at temperatures around 600 degreesC tha t determines their properties in service. In addition to other microstructu ral parameters, the state of the precipitates plays an important role for m icrostructural stability which is a prerequisite for long term creep streng th. In order to support theoretical studies on precipitation growth and coa rsening with more reliable experimental data, in this study a method is int roduced for the quantification of the state of precipitates in (9-12)%Cr st eels which is based on the application of different TEM methods. Therefore up to about 33 000 h aged specimens of the martensitic cast alloy G-X12CrMo WVNbN-10-1-1 were investigated by means of electron microscopy, The applica tion of energy filtering transmission electron microscopy (EFTEM) allowed a reliable quantitative distinction between M23C6, VN, and Laves phases to e stablish the size distribution of these precipitates in different specimens conditions.