Influence of dopant on the thermal properties of two plasma-sprayed zirconia coatings Part I: Relationship between powder characteristics and coating properties

  • R. Harnacha
  • P. Fauchais
  • F. Nardou
Reviewed Paper

Abstract

Plasma- sprayed coatings produced with two zirconia powders (− 90 + 10 µm, spray dried and partially sintered) that were stabilized (9 wt %) with dysprosia (DSZ) and ytterbia (YbSZ) were compared to coat-ings sprayed with a yttria (7 wt %) stabilized zirconia (YSZ) powder (45 + 22 µm, fused and crushed). The YSZ particles in the coating were almost fully molten (less than 0.2 % monoclinic m- phase), with excellent contact between the layered splats (adhesion of 54 MPa). The DSZ particles were only partially melted (3.1 % m- phase), with coating adhesion greater than 34 MPa; the YbSZ particles were less melted (6.1 % m- phase), with coating adhesion of 27 MPa. The thermal properties (diffusivity, a; specific heat, cp; and thermal conductivity, κ) of the coatings were about the same. Under thermal cycling (1 h heating at 1100 °C in a furnace followed by fast cooling for approximately 3 min by air jets) of the coatings sprayed on FeCrAl alloy manufactured by powder metallurgy, the behavior of the DSZ coating was simi-lar to that of the YSZ, whereas the YbSZ coating was partially detached. However, in all cases the percent-age of the monoclinic phase decreased and the ratio of the hexagonal structure increased to 1.013 of the nontransformable tetragonal phase t′.

Keywords

dysprosia partially stabilized zirconia phase structure thermal cycling ytterbia 

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Copyright information

© ASM International 1996

Authors and Affiliations

  • R. Harnacha
    • 1
  • P. Fauchais
    • 1
  • F. Nardou
    • 1
  1. 1.LMCTS-URACNRS 320LimogesFrance

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