Please wait a minute...
Acta Metall Sin  2017, Vol. 53 Issue (9): 1025-1037    DOI: 10.11900/0412.1961.2017.00002
Orginal Article Current Issue | Archive | Adv Search |
Effects of W on Creep Behaviors of Novel Nb-Bearing Austenitic Heat-Resistant Cast Steels at 1000 ℃
Yinhui ZHANG, Qiang FENG
State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
Download:  HTML  PDF(12953KB) 
Export:  BibTeX | EndNote (RIS)      
Abstract  

In order to comply with more stringent emissions and fuel economy regulations worldwide, the operation temperature of exhaust components for automotive gasoline engines is now reaching to as high as 1000 ℃, about 200 ℃ higher than the conventional standard. As a result, the incumbent materials for exhaust manifolds and turbine housings are being pushed beyond their high-temperature strength and oxidation limitations. Therefore, there is an urgent demand from automotive industries to develop novel and cost-effective alloys those durable against these increased temperatures. In this work, the effect of W additions on the creep behavior of a series of Nb-bearing austenitic heat-resistant cast steels is investigated at 1000 ℃ and 50 MPa. Microstructures before and after creep rupture tests are carefully characterized to investigate the microstructural evolution during creep deformation. The minimum creep rate of these alloys shows a trend from decline to rise as the W addition is increased. Microstructural analyses reveal that the W addition does not affect the formation of primary Nb(C, N), whereas significantly improves the precipitation of Cr-rich carbides, as well as accelerating the phase transformation from (Cr, Fe, W)7C3 to (Cr, Fe, W)23C6. Moreover, the excessive addition of W leads to the formation of the interme tallic χ-phase. During creep deformation, the secondary precipitation of nano-scale Nb(C, N) also aids in the strengthening of the creep resistance through pinning the dislocations. However, the cellular Cr-rich phase that contains χ-phase significantly accelerates the nucleation and propagation of creep cracks, thereby increasing the creep rate and decreasing the creep life.

Key words:  automotive gasoline engine,      austenitic heat-resistant cast steel      creep      χ;-phase      solid solution strengthening     
Received:  03 January 2017     
ZTFLH:  TG146.1  
  TG113.2  
Fund: Supported by Ford China University Research Program and Fundamental Research Funds for the Central Universities (No.FRF-IC-16-005)

Cite this article: 

Yinhui ZHANG, Qiang FENG. Effects of W on Creep Behaviors of Novel Nb-Bearing Austenitic Heat-Resistant Cast Steels at 1000 ℃. Acta Metall Sin, 2017, 53(9): 1025-1037.

URL: 

https://www.ams.org.cn/EN/10.11900/0412.1961.2017.00002     OR     https://www.ams.org.cn/EN/Y2017/V53/I9/1025

Alloy Cr Ni Si Mn Nb C N W Fe
4C3N 20.35 9.86 0.60 1.01 2.08 0.43 0.29 - Bal.
4C3N1W 20.38 9.18 0.70 0.95 2.14 0.49 0.30 1.21 Bal.
4C3N3W 21.25 10.08 0.67 0.89 2.31 0.44 0.26 3.14 Bal.
4C3N5W 21.40 9.88 0.60 0.81 2.32 0.40 0.27 4.87 Bal.
Table 1  Measured chemical compositions of the alloys with different W contents (mass fraction / %)
Fig.1  Creep strain-time curves (a) and creep strain rate-time curves (b) of the as-cast alloys under 1000 ℃ and 50 MPa
Alloy Creep life / h Minimum creep rate / 10-8 s-1 Creep strain / %
4C3N 56.2±7.7 11.2±3.4 27.7±4.9
4C3N1W 96.4±2.0 5.1±0.9 16.6±2.1
4C3N3W 130.4±14.6 3.3±1.1 26.1±5.8
4C3N5W columnar 85.2±8.7 3.9±1.0 17.1±2.0
4C3N5W 74.4±15.7 4.3±0.6 16.1±0.3
Table 2  Average creep properties of the as-cast alloys tested at 1000 ℃ and 50 MPa
Fig.2  OM images of typical microstructures in as-cast 4C3N (a), 4C3N1W (b), 4C3N3W (c), 4C3N5W columnar (d) and 4C3N5W (e) alloys
Fig.3  SEM-BSE images of typical microstructures in as-cast 4C3N (a), 4C3N1W (b), 4C3N3W (c), 4C3N5W columnar (d) and 4C3N5W (e) alloys, and high magnification SEM-SE image of the area in Fig.3e (f)
Fig.4  XRD spectrum of the extracted precipitates in as-cast 4C3N5W alloy
Fig.5  EBSD maps showing the as-cast grain size in as-cast 4C3N3W (a) and 4C3N5W columnar (b) alloys
Fig.6  SEM-SE images of typical microstructures after creep rupture tests at 1000 ℃ and 50 MPa in as-cast 4C3N (a), 4C3N1W (b), 4C3N3W (c), 4C3N5W columnar (d) and 4C3N5W (e) alloys, and high magnification SEM-BSE image of the area in Fig.6e (f)
Fig.7  XRD spectrum of the extracted precipitates in as-cast 4C3N5W alloy after creep test at 1000 ℃ and 50 MPa
Alloy Area fraction / % Nb(C, N) number density / mm-1
Nb(C, N) (Cr, Fe, W)7C3 (Cr, Fe, W)23C6
4C3N 2.6±0.4 0.4±0.2 - 52.0±6.1
4C3N1W 2.8±0.2 1.4±0.5 - 58.5±7.7
4C3N3W 2.8±0.7 3.0±0.4 0.9±0.2 58.6±7.8
4C3N5W columnar 2.9±0.3 0.7±0.2 1.3±0.3 51.6±4.0
4C3N5W 3.1±0.9 0.6±0.1 2.3±0.7 59.4±6.3
Table 3  Area fractions of precipitates and Nb(C, N) number density along grain boundaries in the as-cast alloys
Alloy State Fe Cr Ni Si Mn Nb C N W
4C3N As-cast 67.67±2.55 20.58±1.80 10.01±0.25 0.65±0.11 1.00±0.12 0.24±0.05 0.15±0.01 0.06±0.04 -
Crept 70.64±0.33 18.94±0.17 9.73±0.01 0.59±0.01 0.90±0.02 0.25±0.02 0.04±0.01 0.05±0.01 -
4C3N1W As-cast 68.35±0.36 18.37±0.09 9.33±0.02 0.58±0.01 0.90±0.02 0.30±0.03 0.13±0.02 < 0.01 0.92±0.01
Crept 67.41±0.23 19.01±0.08 9.63±0.03 0.74±0.02 1.04±0.02 0.27±0.02 0.01±0.00 0.08±0.02 0.99±0.02
4C3N3W As-cast 64.02±1.16 20.45±0.74 10.27±0.11 0.58±0.05 0.92±0.04 0.30±0.02 0.08±0.01 < 0.01 2.69±0.23
Crept 64.18±0.33 20.12±0.18 10.27±0.10 0.70±0.01 0.97±0.02 0.38±0.14 0.02±0.01 0.02±0.01 2.67±0.03
4C3N5W As-cast 63.52±0.06 20.03±0.33 9.95±0.46 0.52±0.01 0.81±0.02 0.38±0.07 0.09±0.01 < 0.01 3.88±0.23
columnar Crept 62.49±0.38 20.48±0.10 10.52±0.22 0.62±0.01 0.93±0.01 0.38±0.09 0.02±0.00 0.01±0.01 3.97±0.01
4C3N5W As-cast 63.59±0.26 19.81±0.13 10.37±0.06 0.45±0.01 0.82±0.02 0.35±0.00 0.07±0.01 < 0.01 3.75±0.04
Crept 63.65±0.47 20.10±0.03 10.07±0.34 0.53±0.02 0.86±0.02 0.36±0.03 0.02±0.00 < 0.01 3.82±0.07
Table 4  Average chemical compositions of γ austenite in the experimental alloys determined by EPMA(mass fraction / %)
Fig.8  Vickers hardness of the austenitic matrix in the as-cast alloys before and after creep rupture tests at 1000 ℃ and 50 MPa
Fig.9  Bright-field TEM images of the interdendritic (a) and dendritic (c) microstructures in as-cast 4C3N1W alloy after creep ruptured at 1000 ℃ and 50 MPa, and typical SAED patterns of (Cr, Fe, W)23C6 (b) and Nb(C, N) (d) acquired from the respective phases in Figs.9a and c
Fig.10  SEM-BSE images of creep cracks in as-cast 4C3N3W (a) and 4C3N5W columnar (b) alloys after creep rupture tests at 1000 ℃ and 50 MPa
Fig.11  Mass fractions of equilibrium phases as a function of W additions in Nb-bearing austenitic heat-resistant cast steels at 1000 ℃
[1] Matsumoto K, Tojo M, Jinnai Y, et al.Development of compact and high performance turbocharger for 1050 ℃ exhaust gas[J]. Mitsubishi Heavy Ind. Tech. Rev., 2008, 45(3): 1
[2] Kunanoppadon J.Thermal efficiency of a combined turbocharger set with gasoline engine[J]. Am. J. Engg. Applied Sci., 2010, 3: 342
[3] Ebisu M, Terakawa Y, Ibaraki S.Mitsubishi turbocharger for lower pollution cars[J]. Mitsubishi Heavy Ind. Tech. Rev., 2004, 41(1): 40
[4] An B, Shiraishi T.Development of variable two-stage turbocharger for passenger car diesel engines[J]. Mitsubishi Heavy Ind. Tech. Rev., 2010, 47(4): 7
[5] Itoh K, Hayashi K, Souda T.Development of HERCUNITE?-S NSHR?-A5N for high performance gasoline engines[J]. Hitachi Metals Tech. Rev., 2006, 22: 51
[6] Shingledecker J P, Maziasz P J, Evans N D, et al.Creep behavior of a new cast austenitic alloy[J]. Int. J. Pres. Ves. Pip., 2007, 84: 21
[7] Takabayashi H, Ueta S, Shimizu T, et al.Development of thermal fatigue resistant ferritic cast steel for turbine housing of diesel engine automobile[J]. SAE Int. J. Mater. Manuf., 2009, 2: 147
[8] Perron A, Toffolon-Masclet C, Ledoux X, et al.Understanding sigma-phase precipitation in a stabilized austenitic stainless steel (316Nb) through complementary CALPHAD-based and experimental investigations[J]. Acta Mater., 2014, 79: 16
[9] Erneman J, Schwind M, Liu P, et al.Precipitation reactions caused by nitrogen uptake during service at high temperatures of a niobium stabilised austenitic stainless steel[J]. Acta Mater., 2004, 52: 4337
[10] Erneman J, Schwind M, Andrén H O, et al.The evolution of primary and secondary niobium carbonitrides in AISI 347 stainless steel during manufacturing and long-term ageing[J]. Acta Mater., 2006, 54: 67
[11] Yamamoto Y, Brady M P, Santella M L, et al.Overview of strategies for high-temperature creep and oxidation resistance of alumina-forming austenitic stainless steels[J]. Metall. Mater. Trans., 2011, 42A: 922
[12] Pickering F B.Physical Metallurgy and the Design of Steels[M]. London: Applied Science Publishers Ltd, 1978: 12
[13] Medvedeva N I, Van Aken D C, Medvedeva J E. Stability of binary and ternary M23C6 carbides from first principles[J]. Comp. Mater. Sci., 2015, 96: 159
[14] Yamamoto Y, Santella M L, Brady M P, et al.Effect of alloying additions on phase equilibria and creep resistance of alumina-forming austenitic stainless steels[J]. Metall. Mater. Trans., 2009, 40A: 1868
[15] Jung S, Sohn S S, Jo Y H, et al.Effects of Cr and Nb addition on high-temperature tensile properties in austenitic cast steels used for turbo-charger application[J]. Mater. Sci. Eng., 2016, A677: 316
[16] Jung S, Jeon C, Jo Y H, et al.Effects of tungsten and molybdenum on high-temperature tensile properties of five heat-resistant austenitic stainless steels[J]. Mater. Sci. Eng., 2016, A656: 190
[17] Kim Y J, Lee D G, Jeong H K, et al.High temperature mechanical properties of HK40-type heat-resistant cast austenitic stainless steels[J]. J. Mater. Eng. Perform., 2010, 19: 700
[18] Taneike M, Abe F, Sawada K.Creep-strengthening of steel at high temperatures using nano-sized carbonitride dispersions[J]. Nature, 2003, 424: 294
[19] Sherby O D, Burke P M.Mechanical behavior of crystalline solids at elevated temperature[J]. Prog. Mater. Sci., 1968, 13: 323
[20] Rieth M, Falkenstein A, Graf P, et al.Creep of the austenitic steel AISI 316 L(N): Experiments and models [R]. Wissenschaftliche Berichte FZKA 7065, 2004: 1
[21] Zhang Y H, Li M, Godlewski L A, et al.Effects of N/C ratio on solidification behaviors of novel Nb-bearing austenitic heat-resistant cast steels for exhaust components of gasoline engines[J]. Metall. Mater. Trans., 2017, 48A: 1151
[22] Buchanan K, Kral M.Crystallography and morphology of niobium carbide in as-cast HP-niobium reformer tubes[J]. Metall. Mater. Trans., 2012, 43A: 1760
[23] Qiao G W, Wang D H, Cao Z B.An EM study of carbide precipitates in HK40 refractory steel[J]. Acta Metall. Sin., 1986, 22: 67(乔桂文, 王德和, 曹智本. HK40耐热钢碳化物析出的电镜研究[J]. 金属学报, 1986, 22: 67)
[24] Ozbayraktar S, Koursaris A.Effect of superheat on the solidification structures of AISI 310S austenitic stainless steel[J]. Metall. Mater. Trans., 1996, 27B: 287
[25] Zhang Y H, Li M, Godlewski L A, et al.Effective design of new austenitic cast steels for ultra-high temperature automotive exhaust components through combined CALPHAD and experimental approaches[J]. Mater. Sci. Eng., 2017, A683: 195
[26] Zhang Y H, Li M, Godlewski L A, et al.Effects of N on creep properties of austeni-tic heat-resistant cast steels developed for exhaust component applications at 1000 ℃[J]. Acta Metall. Sin., 2016, 52: 661(张银辉, Li M, Godlewski L A等. N对汽车发动机用新型奥氏体耐热铸钢1000 ℃蠕变性能的影响[J]. 金属学报, 2016, 52: 661)
[27] Lo K H, Shek C H, Lai J K L. Recent developments in stainless steels[J]. Mater. Sci. Eng., 2009, R65: 39
[28] Ribeiro E A A G, Papaléo R, Guimar?es J R C. Microstructure and creep behavior of a niobium alloyed cast heat-resistant 26 pct Cr steel[J]. Metall. Trans., 1986, 17A: 691
[29] Zhang Y H, Li M, Godlewski L A, et al.Creep behavior at 1273 K (1000 ℃) in Nb-bearing austenitic heat-resistant cast steels developed for exhaust component applications[J]. Metall. Mater. Trans., 2016, 47A: 3289
[30] Zhang J S.High Temperature Deformation and Fracture of Materials [M]. Beijing: Science Press, 2007: 3(张俊善. 材料的高温变形与断裂 [M]. 北京: 科学出版社, 2007: 3)
[31] Michalska J, Sozańska M.Qualitative and quantitative analysis of σ and χ phases in 2205 duplex stainless steel[J]. Mater. Charact., 2006, 56: 355
[1] WU Jing,LIU Yongchang,LI Chong,WU Yuting,XIA Xingchuan,LI Huijun. Recent Progress of Microstructure Evolution and Performance of Multiphase Ni3Al-Based Intermetallic Alloy with High Fe and Cr Contents[J]. 金属学报, 2020, 56(1): 21-35.
[2] HU Bin,LI Shusuo,PEI Yanling,GONG Shengkai,XU Huibin. Influence of Small Misorientation from <111> on Creep Properties of a Ni-Based Single Crystal Superalloy[J]. 金属学报, 2019, 55(9): 1204-1210.
[3] Wenshu TANG,Junfeng XIAO,Yongjun LI,Jiong ZHANG,Sifeng GAO,Qing NAN. Effect of Re-Heat Rejuvenation Treatment on γ′ Microstructure of Directionally SolidifiedSuperalloy Damaged by Creep[J]. 金属学报, 2019, 55(5): 601-610.
[4] LU Shijie, WANG Hu, DAI Peiyuan, DENG Dean. Effect of Creep on Prediction Accuracy and Calculating Efficiency of Residual Stress in Post Weld Heat Treatment[J]. 金属学报, 2019, 55(12): 1581-1592.
[5] Guodong HU, Pei WANG, Dianzhong LI, Yiyi LI. Precipitate Evolution in a Modified 25Cr-20Ni Austenitic Heat Resistant Stainless Steel During CreepRupture Test at 750 ℃[J]. 金属学报, 2018, 54(11): 1705-1714.
[6] Hongyang XU,Haibo KE,Huogen HUANG,Pei ZHANG,Pengguo ZHANG,Tianwei LIU. Nanoindentation Creep Behavior of U65Fe30Al5 Amorphous Alloy[J]. 金属学报, 2017, 53(7): 817-823.
[7] Xiancui LIU, Ye PAN, Zhijiao TANG, Weiqiao HE, Tao LU. Microstructure Control and High Temperature Properties of Al-Mn-Based Alloys[J]. 金属学报, 2017, 53(11): 1487-1494.
[8] Yinhui ZHANG,Mei LI,Larry A GODLEWSKI,Jacob W ZINDEL,Qiang FENG. EFFECTS OF N ON CREEP PROPERTIES OF AUSTENI-TIC HEAT-RESISTANT CAST STEELS DEVELOPEDFOR EXHAUST COMPONENT APPLICATIONSAT 1000 ℃[J]. 金属学报, 2016, 52(6): 661-671.
[9] Jing ZHANG,Yunrong ZHENG,Qiang FENG. STUDY ON REJUVENATION HEAT TREATMENT OF A DIRECTIONALLY-SOLIDIFIED SUPERALLOYDZ125 DAMAGED BY CREEP[J]. 金属学报, 2016, 52(6): 717-726.
[10] Yongchang LIU, Qianying GUO, Chong LI, Yunpeng MEI, Xiaosheng ZHOU, Yuan HUANG, Huijun LI. RECENT PROGRESS ON EVOLUTION OF PRECIPI-TATES IN INCONEL 718 SUPERALLOY[J]. 金属学报, 2016, 52(10): 1259-1266.
[11] XIE Jun, YU Jinjiang, SUN Xiaofeng, JIN Tao, SUN Yuan. CARBIDE EVOLUTION BEHAVIOR OF K416B AS-CAST Ni-BASED SUPERALLOY WITH HIGH W CONTENT DURING HIGH TEMPERATURE CREEP[J]. 金属学报, 2015, 51(4): 458-464.
[12] LI Weijuan, ZHANG Hengyi, FU Hao, ZHANG Jianping, QI Xiangyu. INTERNAL FRICTION STUDY OF MECHANISM OF BAKE-HARDENING ON LOW CARBON STEEL[J]. 金属学报, 2015, 51(4): 385-392.
[13] SUN Chaoyang, SHI Bing, WU Chuanbiao, YE Naiwei, MA Tianjun, XU Wenliang, YANG Jing. HIGH TEMPERATURE CREEP DEFORMATION MECHANISM OF BSTMUF601 SUPERALLOY[J]. 金属学报, 2015, 51(3): 349-356.
[14] Yong SU,Sugui TIAN,Huichen YU,Lili YU. DEFORMATION MECHANISMS OF Ni-BASED SINGLE CRYSTAL SUPERALLOYS DURING STEADY-STATE CREEP AT INTERMEDIATE TEMPERATURES[J]. 金属学报, 2015, 51(12): 1472-1480.
[15] Shuai SUN,Daxin E. A NOVEL MODEL BASED ON VISCOELASTIC THEO- RY TO PREDICT THE TIME-DEPENDENT SPRINGBACK FOR DP600 STEEL SHEET[J]. 金属学报, 2015, 51(11): 1356-1364.
No Suggested Reading articles found!