N. B. Pugacheva, A. E. Trokhacheva, T. M. Kryuchkova, I. S. Bakhteev

THE EFFECT OF LASER PROCESSING ON THE STRUCTURE AND MICROHARDNESS OF A ZrO2-BASED THERMAL BARRIER COATING

The paper studies the effect of laser processing conditions at powers ranging between 90 and 150 W on a thermal barrier coating consisting of an Y2O3-stabilized ZrO2 outer layer and a NiCrAl metal substrate. The coating is sprayed on the 20Kh4FA steel. Scanning electron microscopy, energy dispersive analysis of the chemical composition of the coating, profilometry, and surface microhardness study were used in the research. The study of the structure, chemical element distribution, microhardness, and surface roughness of the thermal barrier coating has revealed that the laser processing of the surface causes partial melting of the ceramic layer to different depths, depending on laser power. A radiation power of 100 W proves to have the best effect on the state of the ceramic outer layer of the coating; namely, the hardness reaches 953 HV 0.030, there are no Cr, Ni or Fe on the surface, this being indicative of the soundness of the ZrO2+Y2O3 layer. The surface roughness of this coating is the lowest, 7.5 µm. When the processing power exceeds 100 W, there are Cr, Ni, and Fe on the surface; this indicates the presence of defects in the coating and has a detrimental effect on its thermal barrier properties. Besides, a relation has been found between the microhardness and thickness of the preserved metal substrate; namely, the microhardness increases as the substrate thickness decreases.

Acknowledgment: The work was performed under the state assignment for the IES UB RAS, theme No. 124020700063-3. The equipment of the Plastometriya shared research facilities, IES UB RAS, was used for the research.

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