Influence of long-term aging and superimposed creep stress on the microstructure of 2.25cr-1Mo steel

Nondestructive Evaluation of Thermally Degraded 2.25Cr-1Mo Steel by Electrical Resistivity Measurement

“…Comparing the results of diffraction pattern analysis of several carbides with their composition, it was found that carbides had distinct composition depending on the type of carbide such as Cr rich M 23 C 6 , Mo rich M 6 C, Mo 2 C (M 2 C), Fe 3 C (M 3 C). [3][4][5] Gope et al 6) and Watanabe and Shoji 7) reported an increase in M 6 C carbide, which had been previously reported by Baker and Nutting 8) to be a stable carbide, in thermally degraded 2.25Cr-1Mo steel. The increase of Mo rich M 6 C in Cr-Mo type of low alloy steel is reported to cause irreversible carbide-induced embrittlement.…”

“…[1][2][3][4][5][6][7] In order to evaluate the microstructural degradation of CrMo type steel arising from long time exposure to high temperature, composition [3][4][5] or morphology 6) analysis of carbides has been performed to identify the different kind of carbides. Comparing the results of diffraction pattern analysis of several carbides with their composition, it was found that carbides had distinct composition depending on the type of carbide such as Cr rich M 23 C 6 , Mo rich M 6 C, Mo 2 C (M 2 C), Fe 3 C (M 3 C).…”

Microstructural Degradation Assessment in Pressure Vessel Steel by Harmonic Generation Technique

“…The peak intensity of XRD was closely related to the relative volume fraction of any phase (i.e., carbide) in the test materials, due to the strong influences of the amount of diffracted phase and the test conditions. In this ferritic 2.25Cr-1Mo steel, the M 23 C 6 carbide has been reported to be so stable that there was no specific change 15,16) and thus is sufficient as a fixed standard for the majority of precipitates in 2.25Cr-1Mo steel. Therefore, the variation in the volume fraction of M 6 C carbide was measured with the peak intensity ratio (I M 6 C =I M 23 C 6 ) of XRD at each specimen, where I M 6 C and I M 23 C 6 are the peak intensities of M 6 C (42.…”

“…Gope et al classified the morphology of carbides into three types: fine platelet-shaped carbide for Mo 2 C, rectangular parallelpiped carbide for M 23 C 6 , and globular carbide for M 6 C carbide. [15][16][17][18][19][20] The average sizes of globular, rectangular, and acicular carbides were 0.11, 0.13, and 0.03 mm, respectively. All three types of carbides coarsen with increasing degradation time, and their particle sizes range between 0.03 and 0.19 mm.…”

“…The ferritic 2.25Cr-1Mo steel mainly contained M 3 C, M 2 C, M 6 C, M 7 C 3 , and M 23 C 6 carbides. 15) The identification of the phase and lattice parameter of the precipitates prepared by electrolytic extraction was conducted using X-ray diffraction (XRD). Electrolytic extraction was carried out to identify the precipitates in the isothermal degraded specimens by dissolution of the matrix in 10% hydrochloric acid in methanol, as the electrolyte, at a voltage of 3 V for 12 h. The extracted residues were identified by XRD (Cu K radiation).…”