Measurement of residual stress in thermal barrier coating using GIXRD A.M. Kamalan Kirubaharan a , A. Anderson b,⇑ , Nivin Joy Thykattusserry b , M. Rajasekaramoorthy a , M. Surya Saketh a , P. Bhargav a a Centre of Nano Science and Nano Technology, Sathyabama Institute of Science and Technology, Chennai, India b School of Mechanical Engineering, Sathyabama Institute of Science and Technology, Chennai, India article info Article history: Received 28 July 2020 Received in revised form 16 September 2020 Accepted 19 September 2020 Available online xxxx Keywords: Ceramic materials Rare earth materials Thermal barrier coating (TBC) Multilayer coating Residual stress abstract Inconel alloys are widely used in aerospace industry for various components of the gas turbines. These materials have excellent mechanical properties at high temperatures, but they do not provide suitable protection against hot corrosion and oxidation at high temperature. YSZ based Thermal barrier coating (TBC) system is the most widely used in the industry to enhance the life of the alloy. The low thermal conductivity of the YSZ TBC reduces the operating temperature of the alloy to achieve this. But even with YSZ TBC fail at temperatures above 1200⁰C. In order to overcome these limitations YSZ is doped with Gadolinium oxide Gd 2 O 3 in varying compositions. The Inconel 718 alloy was selected as the substrate to be coated and 4 different composition and combinations were coated. There are residual stresses pre- sent in the coatings which can be either beneficial or detrimental. Residual stresses will be generated dur- ing plasma spray deposition and influence on the coating properties. Residual stresses can cause cracking in the surface coatings which leads to decreased durability of the top coat. As a result, the oxidation and corrosion resistance of the alloy decreases at higher temperatures. Residual stress analysis was done on the coatings to find the internal stresses in the coatings using GIXRD process. Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 3rd International Conference on Frontiers in Automobile & Mechanical Engineering. 1. Introduction The turbine blades in turbo rocket engines have to endure high thermo mechanical loads [1]. To increase the lifetime of turbo rocket components, thermal barrier coatings (TBC) may be applied on the components [2]. TBC’s which are thin ceramic coatings applied using various coating techniques to the hot section of the engine [3]. TBC’s have high melting point thus, it can withstand very high temperatures, low thermal conductivity which provides considerable temperature drop across the coating [4,5]. TBC also provide resistance against oxidation, hot corrosion, wear and cal- cium magnesium aluminosilicate (CMAS) attack, etc and provide upto 300 °C temperature drop to the turbines thus increasing their lifetime [6–8]. The most commonly used TBC Yttria stabilized zir- conate (YSZ) has its maximum operating temperatures limited to around 1200 °C [9,10]. The efficiency of the gas turbine engine increases with the increase in operating temperature and thus a TBC system needs to be developed that can operate at higher tem- peratures. Various researches have been carried to find suitable replacement materials to withstand high temperatures. Various researchers are in the way to improve the YSZ performance using a suitable dopants including Titanium oxide, Tantalum oxide, cal- cium oxide, cerium oxide and lanthanum oxide [11–13]. The dopant selected in this research work is Gd 2 O 3. Gadolinium oxide (Gd 2 O 3 ) has high melting point, increased chemical durability, pro- longed thermal stability and low fracture toughness [14]. Residual stress, particularly said to be thermal stress formed during coating will mitigate microcracks which leads to spallation and large size cracks which further hinder the efficiency of the thermal barrier coating and finally failure of coatings occur [15]. In this work gadolinium oxide is doped with YSZ to increase the thermal stabil- ity above 1200⁰C and increase the fracture toughness and which in turn reduce the residual stress formation during coating. 2. Experiment Inconel 718 of size 50mm  30 mm  5 mm is used as a sub- strate. Surface of the substrate are cleaned by acetone and surface prepared by air grit blasting. The bond coat (NiCoCrAly) is plasma https://doi.org/10.1016/j.matpr.2020.09.454 2214-7853/Ó 2020 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the 3rd International Conference on Frontiers in Automobile & Mechanical Engineering. ⇑ Corresponding author. E-mail address: chrisson100@gmail.com (A. Anderson). Materials Today: Proceedings xxx (xxxx) xxx Contents lists available at ScienceDirect Materials Today: Proceedings journal homepage: www.elsevier.com/locate/matpr Please cite this article as: A.M. Kamalan Kirubaharan, A. Anderson, Nivin Joy Thykattusserry et al., Measurement of residual stress in thermal barrier coat- ing using GIXRD, Materials Today: Proceedings, https://doi.org/10.1016/j.matpr.2020.09.454