Aging embrittlement at high temperature of 9Cr3W3Co steel and its improvement method
MA Long-teng1, LIU Zheng-dong1, BAI Yin1,2
1. Institute for Special Steels, Central Iron and Steel Research Institute, Beijing 100081, China;
2. School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
Abstract：The main factor that results in aging embrittlement of 9Cr3W3Co steel was investigated through microstructure observation using scanning electron microscopy (SEM). The amount of each precipitates under equilibrium state in 9Cr3W3Co steel with different W content (W content is 2.36%, 2.63%, 2.96% and 3.11%, mass fraction) was calculated using Thermo-Calc software. The microstructure evolution during aging was studied by transmission electron microscopy (TEM), small angle X-ray scattering (SAXS) and phase analysis method. The results show that the rapid drop of impact toughness after aging for 100h is caused by the formation of Laves phase. The mass fraction of Laves phase at equilibrium state is mainly determined by the concentration of tungsten. The steel with lower tungsten content exhibits higher impact toughness after aging for 8000h,meanwhile with the smallest size and the lowest coarsening rate of Laves phase. Thus, the aging embrittlement of 9Cr3W3Co steel can be successfully suppressed by the reduction of tungsten content.
马龙腾, 刘正东, 白银. 9Cr3W3Co钢高温时效脆化现象与改进方法[J]. 材料工程, 2019, 47(3): 139-146.
MA Long-teng, LIU Zheng-dong, BAI Yin. Aging embrittlement at high temperature of 9Cr3W3Co steel and its improvement method. Journal of Materials Engineering, 2019, 47(3): 139-146.
 PLESIUTSCHNIG E, BEAL C, PAUL S, et al. Optimised microstructure for increased creep rupture strength of MarBN steels[J]. Materials at High Temperatures, 2015, 32(3):318-322.
 LIU Y,TSUKAMOTO S,SAWADA K,et al. Precipitation behavior in the heat-affected zone of boron-added 9Cr-3W-3Co steel during post-weld heat treatment and creep deformation[J]. Metallurgical and Materials Transactions A,2015,46(5):1843-1854.
 ABE F. Analysis of creep rates of tempered martensitic 9%Cr steel based on microstructure evolution[J]. Materials Science and Engineering:A, 2009, 510/511:64-69.
 ABE F, TABUCHI M, TSUKAMOTO S. Alloy design of mart-ensitic 9Cr-boron steel for A-USC boiler at 650℃-beyond grades 91,92 and 122[C]//The 2014 Energy Materials Conference. Xi'an:CSM & TMS, 2014:129-136.
 ABE F. Alloy design of creep-and oxidation-resistant 9%Cr steel for high efficiency USC power plant[J]. Materials Science Forum, 2012, 706/709:3-8.
 ROJAS D, GARCIA J, PRAT O, et al. 9%Cr heat resistant steels:alloy design, microstructure evolution and creep response at 650℃[J]. Materials Science and Engineering:A, 2011, 528(15):5164-5176.
 YAN P, LIU Z, BAO H, et al. Effect of tempering temperature on the toughness of 9Cr-3W-3Co martensitic heat resistant steel[J]. Materials & Design, 2014, 54:874-879.
 YAN P, LIU Z, BAO H, et al. Effect of normalizing temperature on the strength of 9Cr-3W-3Co martensitic heat resistant steel[J]. Materials Science and Engineering:A, 2014, 597:148-156.
 GUO X, JIANG Y, GONG J, et al. The influence of long-term thermal exposure on microstructural stabilization and mechanical properties in 9Cr-0.5Mo-1.8W-VNb heat-resistant steel[J]. Materials Science and Engineering:A, 2016, 672:194-202.
 HOSOI Y, WADE N, KUNIMITSU S, et al. Precipitation behavior of Laves phase and its effect on toughness of 9Cr-2Mo ferritic-martensitic steel[J]. Journal of Nuclear Materials, 1986, 141/143:461-467.
 KOMAZAKI S, KISHI S, SHOJI T, et al. Thermal aging embrittlement of tungsten-alloyed 9%Cr ferritic steels and electrochemical evaluation[J]. Journal of the Society of Materials Science, 2003, 52(3):42-49.
 ZHONG W, WANG W, YANG X, et al. Relationship between Laves phase and the impact brittleness of P92 steel reevaluated[J]. Materials Science and Engineering:A, 2015, 639:252-258.
 YAN P, LIU Z. Toughness evolution of 9Cr-3W-3Co marten-sitic heat resistant steel during long time aging[J]. Materials Science and Engineering:A, 2016, 650:290-294.
 KIPELOVA A,BELYAKOV A,KAIBYSHEV R. Laves phase evolution in a modified P911 heat resistant steel during creep at 923K[J]. Materials Science and Engineering:A, 2012, 532:71-77.
 CUI H, SUN F, CHEN K, et al. Precipitation behavior of Laves phase in 10%Cr steel X12CrMoWVNbN10-1-1 during short-term creep exposure[J]. Materials Science and Engi-neering:A, 2010, 527(29/30):7505-7509.
 ROJAS D, GARCIA J, PRAT O, et al. Design and charact-erization of microstructure evolution during creep of 12% Cr heat resistant steels[J]. Materials Science and Engineering:A, 2010, 527(16/17):3864-3876.
 PRAT O, GARCIA J, ROJAS D, et al. The role of Laves phase on microstructure evolution and creep strength of novel 9%Cr heat resistant steels[J]. Intermetallics, 2013, 32:362-372.
 ABE F. Effect of boron on microstructure and creep strength of advanced ferritic power plant steels[J]. Procedia Engineering, 2011, 10:94-99.
 ALBERT S, KONDO M, TABUCHI M, et al. Improving the creep properties of 9Cr-3W-3Co-NbV steels and their weld joints by the addition of boron[J]. Metallurgical and Materials Transactions A, 2005, 36(2):333-343.
 LEE J, ARMAKI H, MARUYAMA K, et al. Causes of breakdown of creep strength in 9Cr-1.8W-0.5Mo-VNb steel[J]. Materials Science and Engineering:A, 2006, 428(1/2):270-275.
 LI Q. Precipitation of Fe2W laves phase and modeling of its direct influence on the strength of a 12Cr-2W steel[J]. Metallurgical and Materials Transactions A, 2006, 37(1):89-97.
 李太江,刘福广,范长信,等.超超临界锅炉用新型奥氏体耐热钢HR3C的高温时效脆化研究[J].热加工工艺,2010,39(14):43-46. LI T J, LIU F G, FAN C X, et al. Study on aging embrittlement of new type austenitic heat resistant steel HR3C used in USC boiler[J]. Hot Working Technology, 2010, 39(14):43-46.
 刘俊建,陈国宏,王家庆,等.时效热处理对HR3C钢组织结构及力学性能的影响[J].合肥工业大学学报(自然科学版),2011,31(1):47-51. LIU J J, CHEN G H, WANG J Q, et al. Effect of ageing treatment on microstructure and mechanical properties of HR3C steel[J]. Journal of Hefei University of Technology (Natural Science), 2011, 31(1):47-51.
 乔瑞芳,毕洪运,陈玉喜.Ti,Nb和W复合强化超纯铁素体不锈钢的高温析出行为[J].材料工程,2016,44(5):22-28. QIAO R F, BI H Y, CHEN Y X. Precipitation behavior of (Ti, Nb, W)-modified ferritic stainless steel during high-temperature aging[J]. Journal of Materials Engineering, 2016, 44(5):22-28.
 王哲,王新南,祝力伟,等.TB17钛合金等温时效析出行为[J].航空材料学报,2016,36(5):1-6. WANG Z, WANG X N, ZHU L W, et al. Isothermal aging precipitate of TB17 titanium alloy[J]. Journal of Aeronautical Materials, 2016, 36(5):1-6.