Thermal barrier coatings (TBC) are the system build from ceramic insulation top-coat with internal bond-coat as an interlayer between ceramic and Ni-based superalloys substrate materials. The basic role of bond-coat is reduction of thermal strain between ceramic top-coat and metallic substrates. The second role is related to improving the oxidation resistance of metallic substrate. From thermal conductivity point of view, TBC’s system is characterized by three different materials. Usually, bond-coats and Ni-based superalloys were treated as materials with similar thermal properties such as specific heat, thermal diffusivity and thermal conductivity. Actually those materials can exhibit much higher divergences than expected. The aim of this article was the characterization of thermal diffusivity of bond-coats material of NiCrAlY type in the form of powders, massive alloy (obtained during sintering in an actual pressure of 15 MPa, in vacuum of 3 × 10⁻⁶ MPa, and at temperature 1050 °C with 2 h of exposure in press), and coating after air plasma spraying. Those studies should get the answer on the question how different morphology and processes impact on thermal diffusivity level of the same material.

The degradation process of thermal barrier coatings (TBCs) such as monolayered La₂Zr₂O₇, composite 50% La₂Zr₂O₇ + 50% 8YSZ, and double-ceramic layer (DCL) La₂Zr₂O₇/50% La₂Zr₂O₇ + 50% 8YSZ/8YSZ was investigated. Coatings were deposited using the atmospheric plasma spraying (APS) process (ceramic layer and bond-coat) on the Ni-based superalloy substrate with Ni-22Cr-10Al-1Y bond-coat. The thickness of the ceramic top-coats in all cases were 300 µm. In the case of La₂Zr₂O₇/8YSZ, the internal sublayer was built from 8YSZ powder whereas the outer from La₂Zr₂O₇. Between both sublayers’ “composite” a 50% La₂Zr₂O₇ + 50% 8YSZ zone was present. The “composite” 50% La₂Zr₂O₇ + 50% 8YSZ TBC system was sprayed from two different feedstock powders with equal weight ratios. In the first part of the investigation, the microstructural characterization of the TBCs was presented. The main goals were related to the characterization of the degradation processes in different TBC systems with special emphasis on the phenomenon in the thermally grown oxide (TGO) zone related to oxidation, and the phenomenon related to phase stability in ceramic top-coats as related to temperature influence. The oxidation test was carried out in air at 1100 °C for 500 h. In the second step of the investigation, the numerical simulation of the monolayered TBC 8YSZ and La₂Zr₂O₇ systems was analyzed from the stress distribution point of view. Additionally, the two-layered TBC coating of the DCL type was also analyzed.

The basic goal of this article was thermal diffusivity characterization of ceramic materials used in thermal barrier coating (TBC) systems for depositions of the insulation layer and characterization of the materials’ morphology and remanufacturing process. The base material was oxide 8YSZ (ZrO₂ × 8Y₂O₃), which is usually dedicated to deposition of an insulating top layer in TBC systems. The data related to thermal properties such as thermal diffusivity and thermal conductivity are widely presented in the literature, but there is lack of information about the morphological form of investigated materials, and the presented results vary widely. Data on thermal properties based on the literature sources are inadequate for the real morphological form of materials used in the experiment (e.g., massive or single crystalline material vs. plasma-sprayed coatings), which consequently gives an unsatisfactory accuracy of the obtained numerical simulations by MES methods. This article presents the characterization of thermal diffusivity of the commercial 8YSZ ceramic material synthesized or remanufactured by different routes, which is investigated in the forms of pressed powder pellet (two commercial nano-sized powders with different morphologies), sintered pellets (one commercial powder, solid-state co-precipitated reacted powder of 8YSZ type), and a two-layered coating system of In625 + NiCrAlY/8YSZ type. The range of analysis included morphological investigations of different types of powders in initial conditions and after remanufacturing (sintering, thermal spraying) as well as the thermal diffusivity analysis by the laser flash method. The obtained data were corrected by porosity factor and compared to each other. The best similarity for obtained thermal diffusivity data was found for commercial powers of HOSP^TM type after pressing and sintering processes and calculated (2-layered model) value of thermal diffusivity for two-layered system of In625/8YSZ TBS system. The results showed that there are significant differences in thermal diffusivity values for materials with different morphological forms.

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informuj?ce swoich czytelnik?w o najnowszych osi?gni?ciach naukowych i nowoczesnych rozwi?zaniach technicznych w Polsce i na ?wiecie, popularyzuje problemy techniczne oraz poszerza wiedz? i kultur? techniczn?.

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informuj?ce swoich czytelnik?w o najnowszych osi?gni?ciach naukowych i nowoczesnych rozwi?zaniach technicznych w Polsce i na ?wiecie, popularyzuje problemy techniczne oraz poszerza wiedz? i kultur? techniczn?.