Crack-Resistance Behavior of an Encapsulated, Healing Agent Embedded Buffer Layer on Self-Healing Thermal Barrier Coatings

Dowon Song,In-Soo Kim,Yeon-Gil Jung,Ungyu Paik,Guanlin Lyu,Jing Zhang,Baig-Gyu Choi,Taeseup Song

doi:10.3390/coatings9060358

Abstract

In this work, a novel thermal barrier coating (TBC) system is proposed that embeds silicon particles in coating as a crack-healing agent. The healing agent is encapsulated to avoid unintended reactions and premature oxidation. Thermal durability of the developed TBCs is evaluated through cyclic thermal fatigue and jet engine thermal shock tests. Moreover, artificial cracks are introduced into the buffer layer’s cross section using a microhardness indentation method. Then, the indented TBC specimens are subject to heat treatment to investigate their crack-resisting behavior in detail. The TBC specimens with the embedded healing agents exhibit a relatively better thermal fatigue resistance than the conventional TBCs. The encapsulated healing agent protects rapid large crack openings under thermal shock conditions. Different crack-resisting behaviors and mechanisms are proposed depending on the embedding healing agents.

Highlights

Thermal barrier coatings (TBCs) are used to enhance the energy efficiency and durability of hot components of gas turbines or aerospace engines [1,2,3,4,5]
Results and Discussion cracks3.were located above the interface between the top and bond coats within the buffer layer
They were heat-treated at 1000 ◦ C for 100 h, and their healing reaction and detailed crack-resisting

Summary

Introduction

Thermal barrier coatings (TBCs) are used to enhance the energy efficiency and durability of hot components of gas turbines or aerospace engines [1,2,3,4,5]. MCrAlY (M = Ni and/or Co) is usually deposited to form a bond coat layer, which can enhance the bonding strength between the metallic substrate and ceramic top coat and protect the substrate from oxidation and corrosion [5,6,7]. Is typically used as a top coat material because of its excellent thermomechanical properties, such as low thermal conductivity (≈ 2.3 W/(m·K) at 1000 ◦ C), and high coefficient of thermal expansion (CTE), which is similar to the bond coat (top: ≈11·10−6 /◦ C, bond: ≈14 × 10−6 /◦ C) [8,9,10,11,12,13]. During the actual operating service, TBCs are exposed to severe conditions with the following complex phenomena [14,15]: thermomechanical stresses, erosion, corrosion by foreign objects, diffusion, oxidation, phase transformation, and sintering.

Objectives

Results

Conclusion