IN-SITU OBSERVATION OF CARBIDE PRECIPITATION IN DISSIMILAR JOINING OF CR-MO STEEL
Keywords:
PWTH, carbide formation, LEEM, XPS, in-situ observationAbstract
In this study ER90S-B9 welding wire was deposited on 2.25 Cr-1 Mo steel for the joining of dissimilar materials by the gas tungsten arc welding technique. Simulated post weld heat treatment (PWHT) at 700oC was performed under high vacuum in the experimental station BL 3.2 Ub of the Synchrotron Light Research Institute (Public Organization), Nakhon Ratchasima, Thailand for low-energy electron microscopy. Microstructural changes at the weld metal side adjacent to the weld interface were observed. There were black triangular flakes present in the microstructure after the PWHT temperature was reached. They grew in epitaxial alignment with the solidification direction of the weld metal. X-ray photoelectron spectroscopy (XPS) was also implemented on the flakes which could possibly be boron nitride (BN). These flakes were not stable as they decomposed during growth leaving the required elements for carbide precipitation. During the decomposition, 3 regions were observed as black (BN), gray, and white contrasts. Beside boron, Cr and Fe were also indicated in the black and gray regions with the XPS technique. After some decomposition, Cr-rich carbide formed and the hard zone became established. A rough mechanism was proposed as the carbide at the heat affected zone dissolved and carbon migrated to the weld metal by the formation of a BN front followed by the decomposition of the BN which provided elements for carbide precipitation and formation of the hard zone.
References
Abd elmaoula, A.E., Abdelaziz, H.M., Mosa, E. S., Morsi, M. A., and Atlam, A. (2015). Effect of post weld heat treatment and filler metals on microstructures and mechanical properties of GTAW and SMAW weldments between P11 and P91 steels. Int. J. Sci. Eng. Res., 6(4):620-631.
Albert, S.K., Gill, T.P.S., Tyagi, A.K., Mannan, S.L., Kulkarni, S.D., and Rodriguez, P. (1997). Soft zone formation in dissimilar welds between two Cr-Mo steels. Weld. J., 76(3):135-142.
American Society of Mechanical Engineers. (2015). SA-213/SA-213M. Specification for seamless ferritic and austenitic alloy-steel boiler, superheater, and heat-exchanger tubes. American Society of Mechanical Engineers, New York, NY, USA.
American Society of Mechanical Engineers. (2015). SFA-5.28. Specification for low-alloy steel electrodes and rods for gas shielded arc welding. American Society of Mechanical Engineers, New York, NY, USA.
Anand, R., Sudha, C., Paul, V.T., Saroja, S., and Vijayalakshmi, M. (2010). Microstructural changes in grade 22 ferritic steel clad successively with Ni- based and 9Cr filler metals. Weld. J., 89(4):65-s-74-s.
Aronniemi, M., Sainio, J., and Lahtinen, J. (2005). Chemical state quantification of iron and chromium oxides using XPS: the effect of the background subtraction method. Surf. Sci., 578(1-3):108-123.
Biesinger, M. C., Payne, B. P., Grosvenor, A. P., Lau, L. W., Gerson, A. R., and Smart, R. S. C. (2011). Resolving surface chemical states in XPS analysis of first row transition metals, oxides and hydroxides: Cr, Mn, Fe, Co and Ni. Appl. Surf. Sci., 257(7):2,717-2,730.
DuPont, N.J. (2011). Fundamentals of weld solidification. In: ASM Handbook, Volume 6A: Welding Fundamentals and Processes. Lienert, T., Siewert, T., Babu, S., and Acoff, V., (eds). ASM International, Cleveland, OH, USA, p. 96-113.
Foret, R., Zlamal, B., and Sopousek, J. (2006). Structural stability of dissimilar weld between two Cr-Mo-V steels. Weld. J., 85:221-s-217-s.
Gope, N., Mukherjee, T., and Sarma, D.S. (1992). Influence of long- term aging at 520˚C and 560˚C and the superimposed creep stress on the microstructure of 1 . 25Cr - 0 . 5Mo steel. Metall. Trans. A, 23(1):221-235.
Ilton, E. S., Moses, C. O., and Veblen, D. R. (2000). Using X-ray photoelectron spectroscopy to discriminate among different sorption sites of micas: with implications for heterogeneous reduction of chromate at the mica-water interface. Geochim. Cosmochim. Ac., 64(8):1,437-1,450.
Lundin, C.D., Khan, K.K., and Yang, D. (1996) . Report No.1: Effect of carbon migration in Cr-Mo weldments on metallurgical structure and mechanical properties. Weld. Res. Counc. Bull., 407:1-49.
Mayr, P., Schlacher, C., Siefert, J.A., and Parker, J.D. (2018). Microstructural features, mechanical properties and high temperature failures of ferritic to ferritic dissimilar welds. Int. Mater. Rev., 64(1):1-26.
Mittal, R. and Sidhu, B.S. (2014). Microstructural and mechanical characterization of the different zones of the T91/T22 weldment. International Journal of Surface Engineering & Materials Technology, 4(2):45-49.
Mosa, E.S., Abdelaziz, H.M., Morsy, M.A., Abd elmaoula, A.E., and Atlam, A. (2016). Investigation on the influence of post weld heat treatments on weldments between P91 and P11. International Research Journal of Engineering and Technology, 3(11):833-841.
Nelson, T.W., Lippold, J.C., and Mills, M.J. (1999). Nature and evolution of the fusion boundary in ferritic-austenitic dissimilar weld metals, Part 1-Nucleation and growth. Weld. J., 78:329-s-337-s.
Petchsang, S. and Phung-on, I. (2013). Effect of PWHT time on soft zone and hard zone of 2 . 25Cr - 1Mo steel weldment. Engineering Journal, 23(5):59-70.
Race J.M. (1992). Carbon diffusion across dissimilar steel welds, [Ph.D. thesis]. Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, UK, 79p.
Raman, R. S., and Al-Mazrouee, A. (2007). High temperature oxidation of Cr- Mo steels and its relevance to accelerated rupture testing and life assessment of In- service components. Metall. Mater. Trans. A, 38(8):1,750-1,759.
Sae-teaw, N., Poopat, B., Phung-on, I., and Chairuangsri, T. (2010). Analysis of microstructure in soft zone and precipitation zone of dissimilar Cr-Mo steels weldment. Asian International Journal of Science and Technology in Production and Manufacturing Engineering, 2(3):57-64.
Song, X., Gao, J., Nie, Y., Gao, T., Sun, J., Ma, D., Li, Q., Chen, Y., Jin, C., Bachmatiuk, A., and Rümmeli, M. H. (2015). Chemical vapor deposition growth of large-scale hexagonal boron nitride with controllable orientation. Nano Res., 8(10):3,164-3,176.
Sudha, C., Paul, V.T., Terrance, A.L.E., Saroja, S., and Vijayalakshmi, M. (2006). Microstructure and microchemistry of hard zone in dissimilar weldments of Cr-Mo steels. Weld. J., 85(4):71-80.
Sudha, C., Terrance, A.L.E., Albert, S.K., and Vijayalakshmi, M. (2002). Systematic study of formation of soft and hard zones in the dissimilar weldments of Cr–Mo steels. J. Nucl. Mater., 302(2-3):193-205.
Sun, J., Lu, C., Song, Y., Ji, Q., Song, X., Li, Q., Zha, Y., Zha, L., Ko, J., and Liu, Z. (2018). Recent progress in the tailored growth of two-dimensional hexagonal boron nitride via chemical vapour deposition. Chem. Soc. Rev., 47(12):4,242-4,257.
Tammasophon, N., Homhrajai, W., and Lothongkum, G. (2011). Effect of postweld heat treatment on microstructures and hardness of TIG weldment between P22 and P91 steels with Inconel 625 filler metal. Journal of Metals Materials and Minerals, 21(1):93-99.
Yamamoto, S. (2008). Arc welding of specific steels and cast irons. Shinko Welding Service Co. Ltd., Kanagawa, Japan.
You, Y.Y., Shiue, R.K., Shiue, R.H., and Chen, C. (2001). The study of carbon migration in dissimilar welding of the modified 9Cr-1Mo steel. J. Mater. Sci. Lett., 20(15):1,429-1,432
