High-Temperature Cycling of Plasma Sprayed Multilayered NiCrAlY/YSZ/GZO/YAG Thermal Barrier Coatings Prepared from Liquid Feedstocks

Abstract

High-enthalpy hybrid water/argon-stabilized plasma (WSP-H) torch may be used for efficient deposition of coatings from dry powders, suspensions, and solutions. WSP-H torch was used to deposit two complete thermal barrier coatings (TBCs) with multilayered top-coat. NiCrAlY was used as bond - coat and deposited on nickel-based superalloy substrates. Top-coat consisted of up to three sublayers: (i) yttria-stabilized zirconia (ZrO 2 -8 wt.%Y 2 O 3 -YSZ) deposited from solution, (ii) gadolinium zirconate (Gd 2 Zr 2 O 7 -GZO) deposited from suspension, and (iii) optional yttrium aluminum garnet (Y 3 Al 5 O 12 -YAG) overlayer deposited from suspension. Each of the sublayers was intended to provide different functionalities, namely improved fracture toughness, low thermal conductivity, and high erosion resistance, respectively. High-temperature performance and thermal shock resistance of the deposited coatings were tested by thermal cycling fatigue “TCF” test (maximum temperature 1100 °C, 1 h dwell per cycle) and “laser-rig” test (maximum temperature ~ 1530 °C, 5 min dwell per cycle) exposing samples to isothermal and gradient thermal conditions, respectively. In both tests, coatings endured around 800 test cycles which shows great potential for further development of these layers and their application in demanding thermal conditions. Analysis of the samples after the test showed microstructural changes and identified reason of ultimate coating failure.

Evaluation of Localized Spallation of TBCs via a Combination of Conjugate Heat Transfer Numerical and Experimental Analysis

“…They found that the heat transfer coefficient of the surface was higher than that in the spallation region, which can explain the temperature variation between the TC layer and the exposed BC layer in the numerical results. Musalek et al [39] conducted thermal gradient tests of TBCs and observed the localized spallation in the TBCs. They found that although the BC layer in the spallation region was exposed to a high temperature and the TBC surface temperature was higher than the melting point of the BC layer, no BC layer melting was observed in the test.…”

Submicron-thick yttria-stabilized zirconia coating as an advanced tritium permeation barrier

“…Based on the above results, we conceived an idea of utilizing these coating materials to cover the shortcomings: Li-Pb compatibility and high-temperature stability. Yttria-stabilized zirconia (YSZ) is utilized widely in the fields of material science and technology [9][10][11]. In general, the properties of YSZ bulks change depending on the amount of doped Y 2 O 3 to ZrO 2 .…”