Microstructure Evaluation During Short Term Creep of Cr35Ni45Nb Cast Alloy Reformer Tube

다국어 초록 (Multilingual Abstract)

In this work, a Cr35Ni45Nb alloy tube for use in a reformer furnace is subjected to high temperature (871 °C and 927 °C)creep regimes, and the microstructural changes (e.g. carbide precipitation and phase transformation) and consequent creepdamage are investigated. The results of creep tests under closely similar applied stresses give different values of the Larson–Miller parameter (LMP) at different temperatures. As a result, the calculated creep rupture time at 871 °C based on theLMP value measured at 927 °C is approximately twice that which was actually measured at 871 °C. The microstructure ofthe as-cast tube is found to consist of an austenitic matrix with networks of MC (NbC) and eutectic (M23C6) carbides locatedboth at grain boundaries and between dendrites. It is noted that the M23C6carbide is not a primary eutectic carbide that canbe observed in the as-cast Cr35Ni45Nb alloys. It can be argued that the primary eutectic M7C3carbides were transformedinto M23C6due to the heat of spiral welding during the tube manufacturing process. After creep, the NbC carbides at bothlocations were mostly transformed to the G-phase (Nb3Ni2Si) and all the precipitates formed inside the austenitic matrixwere composed of the M23C6and G-phase. Creep cavities were initiated around the G-phase and grew cracks along the grainboundaries due to the formation of a Cr-depleted zone and the G-phase.

참고문헌 (Reference)

1 J. M. Gong, 6 : 143-, 1999

2 Y. Wang, 49 : 1264-, 2018

3 M. Attarian, 68 : 32-, 2016

4 A. Ul-Hamid, 13 : 1005-, 2006

5 P. Berthod, 2012 : 1-, 2012

6 P. Saravanan, 11 : 286-, 2011

7 E. A. Kenik, 49 : 117-, 2003

8 L. H. D. Almeida, 49 : 219-, 2003

9 I. A. S. Torres, 133 : 1018-, 2012

10 M. Attarian, 30 : 112-, 2017

11 B. Hu, 36 : 489-, 2019

12 Y. Zhao, 649 : 1-, 2016

13 J. Rodríguez, 45 : 25-, 2000

14 J. Rodríguez, 17 : 188-, 2013

15 J. Guo, 79 : 625-, 2017

16 L. Bonaccorsi, 36 : 65-, 2014

17 A. Alvino, 17 : 1526-, 2010

18 F. Tancret, 34 : 1333-, 2018

19 A. Ghatak, 25 : 2000-, 2016

20 S. A. Shahrani, 13 : 731-, 2013

21 A. K. Ray, 10 : 351-, 2003

22 J. Guo, 23 : 449-, 2018

23 E. Karantzalis, 22 : 448-, 2009

24 이영민, "Study on the Slope Change in the Larson-Miller Plot of 23Cr-26Ni-W Austenitic Heat-Resistant Steel" 대한금속·재료학회 20 (20): 233-241, 2014

25 E. Guglielmino, "Handbook of Material Failure Analysis with Case Studies from the Chemicals, Concrete, and Power Industries" Elsevier 69-, 2015

26 Van Hung Dao, "Creep deformation characteristics of microalloyed HP40Nb steel at 950℃" 대한기계학회 33 (33): 4813-4821, 2019

27 유종민, "Asymptotic creep deformation behavior of modified HP steel after long-term service" 대한기계학회 34 (34): 1997-2009, 2020

28 K. Cooperation, "Alloy data sheet KHR45A" Kubota Metal Corporation

29 T.R. Dulski, "A Manual for the Chemical Analysis of Metals" American Society for Testing and Materials 70-81, 1996