Thermal cycling and oxidation behavior of lanthanum zirconate/yttria stabilized zirconia based thermal barrier coatings
Mathanbabu Mariappan, D. Thirumalaikumarasamy, Ashokkumar Mohankumar, Thirumal Pattabi
Abstract
Abstract Thermal barrier coatings (TBCs) enhance oxidation resistance and thermal insulation, protecting turbine blades in aero engines at high temperatures. While 8 wt.% Y 2 O 3 -stabilized ZrO 2 (8 YSZ) is widely used, it degrades above 1,200 °C. Lanthanum zirconate (La 2 Zr 2 O 7 , LZ) offers better phase stability, lower sintering potential, and reduced thermal conductivity, making it a promising alternative. In this study, LZ and YSZ feedstocks were blended in weight ratios (100:0, 75:25, 50:50, 25:75) to integrate the advantages of both and applied to Inconel 718 substrates using atmospheric plasma spraying (APS). Thermal cycling at 1,100 °C was conducted to assess thermal insulation and oxidation resistance. Porosity percentages of 100 % LZ, 75 % LZ, 50 % LZ, and 25 % LZ coatings before and after thermal cycling were 9.16, 7.12, 4.45, 4.39 and 2.39, 1.63, 1.6, 1.43, respectively. The thermally grown oxide (TGO) thickness after 100 h is 10 µm, 9 µm, 6 µm, and 5 µm, respectively. Coatings with 25 % and 50 % LZ showed enhanced thermal insulation and oxidation resistance, reducing delamination due to controlled TGO growth. The 25 % LZ coating exhibited a slower oxidation rate than 100 % LZ, with improved oxygen resistance due to the pyrochlore structure, reducing TGO growth and weight gain. Incorporating YSZ into LZ coatings enhanced oxidation resistance and prolonged TBC spallation life under high-temperature conditions. This combination effectively improves TBC performance in demanding environments.