Evaluating the oxidation resistance of bond coats on thermal barrier coatings

Selected from Soldagem & Inspeção 2015 20(4) 479–488.

Abstract

Coatings are being increasingly used as an engineering alternative for advanced projects. Various techniques and processes are available for applying coatings, depending on the specific situation they are intended for. Thermal barrier coatings, known as TBCs, form part of a particular series of metal-ceramic coatings that are traditionally used in the aeronautical industry and are being increasingly applied in the automotive industries and for industrial turbines. One of the main issues with TBCs is degradation owing to the oxidation of the bond coat in high temperatures, resulting in the failure of the coating due to peel off. This study investigates and compares the behaviour of the oxidation of the TBC bond coat when the material used is NiAl alloy; this alloy is commonly used because of its characteristics at high temperatures and to ensure strong adhesion on various substrates. The bond coat was applied on an AISI 1020 Steel substrate using the flame spraying process. In order to carry out isothermal oxidation tests, the furnace used was regulated at a temperature of 1000 °C in static air. The samples were exposed for 24, 48 and 96 h and cooling was carried out in atmospheric air at ambient temperature. The analysis of the thermally grown oxide for each sample was carried out based on the exposure times and the oxide rates were evaluated by measuring the mass gained by the samples with oxidized coatings and using Scanning Electron Microscopy and Optical Microscopy.

Keywords:

• Coating
• TBC
• thermal barrier
• thermal spraying
• oxidation

Acknowledgements

The authors would like thank CNPq (National Council for Technological and Scientific Development) for its financial support and OGRAMAC Engenharia de Superfícies (Surface Engineering) for its technical support with carrying out coatings.

Notes

Selected from Soldagem & Inspeção 2015 20(4) 479–488.