Formation and Evolution of Microstructures in Fe–9%Cr Heat-Resistant Steel

doi:10.1007/s40195-014-0080-0

Abstract

Abstract:

Microstructures of casting samples of Fe–9%Cr steel and samples subjected to different heat treatments were investigated to determine their formation and evolution mechanism. The results show that there is no macroscopic segregation in the casting Fe–9%Cr steel. During cooling from solidification temperature to room temperature, δ-ferrite → austenite transformation is obviously influenced by cooling rate, while subsequent transformation of austenite does not obviously depend on the cooling rate. In the casting samples, a great number of precipitates distribute inside martensitic laths while there are almost no precipitates inside δ-ferrite. When the casting samples were reheated to and isothermally held at 800 °C, the original precipitates and the lath boundaries disappeared gradually. Meanwhile, new precipitates nucleate and grow at the prior lath boundaries.

Key words: Heat-resistant steel, Microstructure, Precipitates, δ-Ferrite, Casting

Boling Zhu, Shanwu Yang, Guangshan Yang, Guoliang Liu. Formation and Evolution of Microstructures in Fe–9%Cr Heat-Resistant Steel[J]. Acta Metallurgica Sinica (English Letters), 2014, 27(3): 534-538.

Figures/Tables 7

Fig. 1 Scheme of sampling for measuring the macroscopic distribution of alloy elements, hardness

Table 1 Macroscopic distribution of alloy elements at different sites in the casting Fe–9%Cr steel

Site	W (wt%)	V (wt%)	Ta (wt%)
Top	1.46	0.20	0.12
Bottom	1.46	0.20	0.12
Middle	1.60	0.21	0.13

Table 2 Variation of hardness with different sites in the casting Fe–9%Cr steel

Site	Hardness (HV)	Error range (HV)
A	395.4	5.8
B	392.8	3.2
C	391	1.4
D	389.9	0.3
E	383.1	-6.5
F	389.2	-0.4
G	389.0	-0.6
H	390.2	0.6
I	386.8	-2.8
J	392.4	2.8
K	389.6	0
L	385.6	-4

Fig. 2 Microstructures and precipitates in the casting sample: a metallograph showing the microstructure of casting sample; b TEM image showing the dislocations in δ-ferrite; c TEM image showing the distribution of precipitates; d EDS results of the precipitate denoted by the frame in c

Fig. 3 SEM images of samples after held at 800 °C for different times: a as-cast; b 32 h; c 67 h; d 200 h

Fig. 4 Variation of hardness with controlled cooling rate in 0.1–25 °C/s from 1,350 to 1,000 °C, 0.1–25 °C/s from 1,000 to 400 °C

Fig. 5 OM images of samples subjected to controlled cooling from 1,350 to 1,000 °C at different rates: a 5 °C/s; b 10 °C/s; c 25 °C/s

References 18

[1]	V.G. Prokoshkina, L.M. Kaputkina, Y.I. Lonjnikov, J. Mater. Process. Technol. 125–126, 97(2002)10.1016/S0924-0136(02)00325-4
[2]	Z.L. Xiong, Q.W. Cai, H.T. Jiang, J. Iron. Steel Res. Int. 17, 38(2010)10.1016/S1006-706X(10)60181-1
[3]	F. Masuyama, ISIJ Int. 41, 612(2001)10.2355/isijinternational.41.612
[4]	F. Abe, M. Taneike, K. Sawada, Int. J. Press. Vessel. Pip. 84, 3(2007)10.1016/j.ijpvp.2006.09.003
[5]	R.L. Klueh, D.S. Gelles, S. Jitsukawa, A. Kimura, G.R. Odette, B. Van der Schaaf, M. Victoria, J. Nucl. Mater. 307–311, 455(2002)10.1016/S0022-3115(02)01082-6
[6]	S. Jitsukawa, M. Tamura, B. van der Schaaf, R.L. Klueh, A. Alamo, C. Petersen, M. Schirra, P. Spaetig, G.R. Odette, A.A. Tavassoli, K. Shiba, A. Kohyama, A. Kimura, J. Nucl. Mater. 307–311, 179(2002)10.1016/S0022-3115(02)01075-9
[7]	Q.Y. Huang, Y.C. Wu, J.G. Li, F.R. Wan, J.L. Chen, G.N. Luo, X. Liu, J.M. Chen, Z.Y. Xu, X.G. Zhou, X. Ju, Y.Y. Shan, J.N. Yu, S.Y. Zhu, P.Y. Zhang, J.F. Zhang, X.J. Chen, S.M. Dong, J. Nucl. Mater. 386–388, 400(2009)10.1016/j.jnucmat.2008.12.158
[8]	G. Lothongkum, E. Viyanit, P. Bhandhubanyong, J. Mater. Process. Technol. 110, 233(2001)10.1016/S0924-0136(00)00875-X
[9]	M. Vasudevan, A.K. Bhaduri, B. Raj, K.P. Rao, J. Mater. Process. Technol. 142, 20(2003)10.1016/S0924-0136(03)00430-8
[10]	J. Oñoro, J. Mater. Process. Technol. 180, 137(2006)10.1016/j.jmatprotec.2006.05.014
[11]	M. Tamura, H. Kusuyama, K. Shinozuka, H. Esaka, J. Nucl. Mater. 367–370, 137(2002)
[12]	K. Sawada, M. Taneike, K. Kimura, F. Abe, ISIJ Int. 44, 1243(2004)10.2355/isijinternational.44.1243
[13]	Y.Z. Shen, S.H. Kim, H.D. Cho, H.H. Chang, S.R. Woo, Nucl. Eng. Des. 239, 648(2009)10.1016/j.nucengdes.2008.12.018
[14]	F. Abe, T. Horiuchi, M. Taneike, K. Sawada, Mater. Sci. Eng. A 378, 299(2004)10.1016/j.msea.2003.11.073
[15]	Y. Murata, K. Yamashita, M. Morinaga, T. Hara, K. Miki, T. Azuma, T. Ishiguro, R. Hashizume, J. Solid Mech. Mater. Eng. 3, 457(2009)10.1299/jmmp.3.457
[16]	S. Raju, B.J. Ganesh, A.K. Rai, R. Mythili, S. Saroja, B. Raj, J. Nucl. Mater. 405, 59(2010)10.1016/j.jnucmat.2010.07.036
[17]	X.Q. Hu, N.M. Xiao, X.H. Luo, D.Z. Li, Acta Metall. Sin. 45, 553(2009). (in Chinese)
[18]	L.Q. Chen, Z.Y. Zeng, Y. Zhao, F.X. Zhu, X.H. Liu, Metall. Mater. Trans. A 45, 1498(2014)10.1007/s11661-013-2105-0