Influence of laser-glazing on hot corrosion resistance of yttria-stabilized zirconia TBC in molten salt mixture of V2O5 and Na2SO4
✍ Scribed by X. Zhong; Y. Wang; Z. Xu; Y. Zhang; J. Zhang; X. Cao
- Publisher
- John Wiley and Sons
- Year
- 2009
- Tongue
- German
- Weight
- 562 KB
- Volume
- 60
- Category
- Article
- ISSN
- 0947-5117
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✦ Synopsis
Abstract
Plasma‐sprayed 8YSZ (zirconia stabilized with 8 wt% yttria)/NiCoCrAlYTa thermal barrier coatings (TBCs) were laser‐glazed using a continuous‐wave CO~2~ laser. Open pores within the coating surface were eliminated and an external densified layer was generated by laser‐glazing. The hot corrosion resistances of the plasma‐sprayed and laser‐glazed coatings were investigated. The two specimens were exposed for the same period of 100 h at 900 °C to a salt mixture of vanadium pentoxide (V~2~O~5~) and sodium sulfate (Na~2~SO~4~). Serious crack and spallation occurred in the as‐sprayed coating, while the as‐glazed coating exhibited good hot corrosion behavior and consequently achieved a prolonged lifetime. The results showed that the as‐sprayed 8YSZ coating achieved remarkably improved hot corrosion resistance by laser‐glazing. Changes in the coatings were studied by scanning electron microscopy (SEM) to observe the microstructure and X‐ray diffraction (XRD) technique to analyze the phase composition. XRD results showed that the reaction between yttria (Y~2~O~3~) and V~2~O~5~ produced yttrium vanadate (YVO~4~), leaching Y~2~O~3~ from YSZ and causing the progressive destabilization transformation from the tetragonal (t) to monoclinic (m) phase. The external dense layer produced by laser‐glazing restrained the penetration of the molten salt, to a certain extent, into the coating, which led to a relatively low m‐ZrO~2~ content in the coating after the hot corrosion test. Additionally, the segmented cracks in the coating surface induced by laser‐glazing were helpful to the improvement of strain tolerance of the coating. The two factors were important contributions to the significant enhancement of hot corrosion resistance of the as‐glazed YSZ coating.