Comparative Study of Oxides Formed on Fusion Zone and Base Metal of Laser Welded Zr-1.0Sn-1.0Nb-0.1Fe Alloy
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Numerous studies have primarily focused on the corrosion mechanism of zirconium alloy base metal. However, the corrosion resistance of weld beads or seams is of vital importance in the degradation of structural components in the reactor. In the present work, the corrosion resistance of the fusion zone and base metal of laser welded zirconium alloy joints was comparatively investigated. The microstructure morphologies, phase structures and strain fields of oxide films formed on fusion zone and base metal were observed and analyzed. The oxide thickness of the fusion zone was thicker than that of the base metal with prolonged corrosion. Compared to the base metal, the lower density of dislocations and level of strain values in the oxide film of the fusion zone indicated that the stress in the oxide film was lower. The phase transition from the tetragonal ZrO2 to the monoclinic ZrO2 could be suppressed due to the high level of stress, resulting in the better corrosion resistance of the base metal. Moreover, the second phase particles and non-βZr phase in the base metal contributed to the better corrosion resistance.
Keywordsgrain morphology laser welded fusion zone oxide film strain field zirconium alloys
The gratitude was expressed to Mrs. Xue Hou and Mr. Huirong Zhao for their help in the corrosion experiments. The authors appreciated the help from Mrs. Xue Liang and Mr. Long Xu for the TEM experiments. We also appreciated Dr. Caiwang Tan for the valuable suggestions.
- 3.N. Ni, S. Lozano-Perez, J.M. Sykes, G.D.W. Smith, and C.R.M. Grovenor, Focussed Ion Beam Sectioning for the 3D Characterisation of Cracking in Oxide Scales Formed on Commercial ZIRLO™ Alloys During Corrosion in High Temperature Pressurised Water, Corros. Sci., 2011, 53, p 4073–4083CrossRefGoogle Scholar
- 6.N.B. Pilling and R.E. Bedworth, The Oxidation of Metals at High Temperatures, J. Inst. Met., 1923, 29, p 529–591Google Scholar
- 22.J. Wei, P. Frankel, E. Polatidis, M. Blat, A. Ambard, R.J. Comstock, L. Hallstadius, D. Hudson, G.D.W. Smith, C.R.M. Grovenor, M. Klaus, R.A. Cottis, S. Lyon, and M. Preuss, The Effect of Sn on Autoclave Corrosion Performance and Corrosion Mechanisms in Zr-Sn-Nb Alloys, Acta Mater., 2013, 61, p 4200–4214CrossRefGoogle Scholar
- 25.S.G. McDonald, Mechanism of Accelerated Corrosion in Zircaloy-4 Laser and Electron-Beam Welds, in Zirconium in the Nuclear Industry: Fifth International Symposium (ASTM STP 754, American Society for Testing and Materials, 1982).Google Scholar
- 32.G.P. Sabol, G.P. Kilp, M.G. Balfour, E. Roberts, Development of a Cladding Alloy for High Burnup, in 8th International Symposium, Zirconium in the Nuclear Industry (ASTM International, STP 1023, San Diego, 1989), p 227–244Google Scholar
- 34.N. Ni, D. Hudson, J. Wei, P. Wang, S. Lozano-Perez, G.D.W. Smith, J.M. Sykes, S.S. Yardley, K.L. Moore, S. Lyon, R. Cottis, M. Preuss, and C.R.M. Grovenor, How the Crystallography and Nanoscale Chemistry of the Metal/Oxide Interface Develops During the Aqueous Oxidation of Zirconium Cladding Alloys, Acta Mater., 2012, 60, p 7132–7149CrossRefGoogle Scholar