The Microstructural Criterion for Creep Strength Breakdown in a 10%Cr Martensitic Steel

Abstract:

A 10%Cr martensitic steel with 3%Co and 0.008%B tempered at 770°C exhibits no creep strength breakdown at a temperature of 650°C up to an extremely high rupture time of ∼4×10⁴ h under an applied stress of 120 MPa. The minimum creep rate was ∼3×10^-11 s^-1. Microstructural characterization showed that superior creep resistance associated with a high stability of tempered martensite lath structure. Boundary M₂₃(B⋅C)₆ phase particles are highly stable against coarsening under long-term aging and creep conditions. These particles retain their orientation relationship with ferritic matrix unchanged under creep at a temperature of 650°C. As a result, no migration of lath boundaries and their transformation to subboundaries diminishing the long-range elastic stress fields take place. The role of M(C,N) carbonitrides in achieving extraordinary high creep strength consists in hindering the knitting reaction between mobile lattice dislocations and lath boundaries.

• Periodical: Materials Science Forum (Volume 879)
• Pages: 465-470
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.879.465
• Online since: November 2016
• Authors: Nadezhda Dudova*, Roman Mishnev, Rustam Kaibyshev
• Keywords: Long-Term Aging, Long-Term Creep, M₂₃C₆ Carbide, Martensite, Z-Phase

References

[1] F. Abe, T. -U. Kern, R. Viswanathan Creep-resistant steels. Woodhead Publishing, Cambridge, 2008, 669 p.

[2] R.O. Kaybyshev, V.N. Skorobogatykh, I.A. Shchenkova, New martensitic steels for fossil power plant: creep resistance, Phys. Met. Met. 109 (2010) 186–200.

DOI: 10.1134/s0031918x10020110

[3] J.S. Lee, H. Gh. Armaki, K. Maruyama, T. Muraki, H. Asahi, Causes of breakdown of creep strength in 9Cr-1. 8W-0. 5Mo-VNb steel, Mater. Sci. Eng. A 428 (2006) 270–275.

DOI: 10.1016/j.msea.2006.05.010

[4] W. Bendick, L. Cipolla, J. Gabrel, J. Hald, New ECCC assessment of creep rupture strength for steel grade X10CrMoVNb9-1 (Grade 91), Int. J. Press. Vessel. Pip. 87 (2010) 304-309.

DOI: 10.1016/j.ijpvp.2010.03.010

[5] M. Yoshizawa, M. Igarashi, K. Moriguchi, A. Iseda, H. Gh. Armaki, K. Maruyama, Effect of precipitates on long-term creep deformation properties of P92 and P122 type advanced ferritic steels for USC power plants, Mater. Sci. Eng. A 510–511 (2009).

DOI: 10.1016/j.msea.2008.05.055

[6] A. Fedoseeva, N. Dudova, R. Kaibyshev, Creep strength breakdown and microstructure evolution in a 3%Co modified P92 steel, Mater. Sci. Eng. A 654 (2016) 1-12.

DOI: 10.1016/j.msea.2015.12.027

[7] R. Kaibyshev, R. Mishnev, E. Tkachev, N. Dudova, Effect of Ni and Mn on the creep behavior of 9-10%Cr steels with low N and high B, Trans. Indian Inst. Met. 69 (2016) 203-210.

DOI: 10.1007/s12666-015-0761-z

[8] H. Semba, F. Abe, Alloy design and creep strength of advanced 9%Cr USC boiler steels containing high concentration of boron, Energy Mater. 1 (2006) 238-244.

DOI: 10.1179/174892406x173611

[9] M. Tabuchi, H. Hongo, F. Abe, Creep strength of dissimilar welded joints using high B-9Cr steel for advanced USC boiler, Metall. Mater. Trans. A 45 (2014) 5068-5075.

DOI: 10.1007/s11661-014-2471-2

[10] Y. Liu, S. Tsukamoto, K. Sawada, M. Tabuchi, F. Abe, Precipitation behaviour in Ac3 HAZ simulated B steel during PWHT and creep deformation, Metal. Mater. Trans. A 46 (2015) 1843-1854.

DOI: 10.1007/s11661-015-2802-y

[11] N. Dudova, R. Mishnev, R. Kaibyshev, Effect of tempering on microstructure and mechanical properties of boron containing 10%Cr steel, ISIJ Int. 51 (2011) 1912-(1918).

DOI: 10.2355/isijinternational.51.1912

[12] K. Kimura, K. Sawada, H. Kushima, K. Kubo, Effect of stress on creep deformation property of ASME Grade P92/T92 steels, Int. J. Mat. Res. 99 (2008) 395-401.

DOI: 10.3139/146.101651

[13] P.R. Howell, J.V. Bee and R.W.K. Honeycombe, The crystallography of the austenite-ferrite/carbide transformation in Fe-Cr-C alloys, Metall. Trans. A 10 (1979) 1213-1222.

DOI: 10.1007/bf02811976