Journal of Thermal Spray Technology

, 5:431

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

DOI: 10.1007/BF02645273

Cite this article as:
Harnacha, R., Fauchais, P. & Nardou, F. JTST (1996) 5: 431. doi:10.1007/BF02645273

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

dysprosiapartially stabilized zirconiaphase structurethermal cyclingytterbia

Copyright information

© ASM International 1996

Authors and Affiliations

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