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Microstructure, mechanical and thermal properties of YSZ thermal barrier coatings deposited by axial suspension plasma spraying

100%

Poliarus O. , Morgiel J. , Żórawski W. , Góral A. , Pomorska M. , Wojciechowski K. T. , Cherniushok O.

Archives of Civil and Mechanical Engineering

2023

tom Vol. 23, no. 2

art. no., e89, 2023

Yttrium-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) are indispensable elements of present-day turbine propulsion systems. The ones deposited with atmospheric plasma spraying (APS) are characterized by required low thermal conductivity, but they are unable to survive frequent thermomechanical loading and therefore their application is limited to parts remaining stationary. Expanding capability of TBCs is sought in various areas, but the one realized through modification of most proliferated apparatus used for plasma spraying (PS) (from radial to axial injection) and substituting micrometric powders with the nano-structured suspension needs least changes in the industry established procedures and offers the highest property improvement. The present experiment covered the deposition of ZrO2-8Y2O3 YSZ TBC using both atmospheric and suspension PS processes. They were performed with commercial micrometric and nano-structured YSZ (8% Y2O3) powders. The coatings morphology and microstructure were characterized with 3D profilometry, scanning and transmission electron microscopy (SEM/TEM) methods. Finally, the coating’s hardness and heat conductivity were measured. This complex approach allowed to state that PS of micrometric t’-ZrO2 powder having an admixture of m-ZrO2 phase is capable of only partial improvement in its homogenization. However, the suspension PS process of nano-structured powder eliminated any traces of the monoclinic phase from the coating. The TEM microstructure observations indicated that the suspension PS coating is built by in-flight solidified droplets as well as by the melted ones flattened on arrival. A surface layer of liquefied material on solid droplets increases their adhesion to surface asperities promoting pseudo-columnar growth of the coating. The preservation of monotonic slow increase of thermal conductivity during heating of the suspension PS coating means, that its pseudo-columnar microstructure is better suited to withstand high strains during such treatment.

Structure and strength characteristics of NiAl-based composite materials

100%

Poliarus O. , Umanskyi O. , Morgiel J. , Bobrowski P. , Szlezyner M. , Mosina T. , Martsenyuk I.

Composites Theory and Practice

2019

tom R. 19, nr 4

169--173

In this paper, the structure of NiAl-15wt.%CrB2, NiAl-15wt.%ZrB2 and NiAl-15wt.%TiB2 composite compact materials was studied using SEM. The composites were obtained by sintering in vacuum. The phase composition was studied by XRD analysis. The effect of the diboride additives on the NiAl hardness was studied. It is shown that the initial intermetallic had a hardness of 288 HV20. At the same time, the hardness value for the NiAl-15wt.% ZrB2 composite is 349 HV20, for NiAl-15wt.%TiB2 it is 392 HV20 and for the NiAl-15wt.%CrB2 composite material it is 468 HV20.