Development of Bond Coat on Superalloy by Laser Cladding and performances evaluation

Problem Statement:

Aerospace engine parts need to be coated with the thermal barrier coating (TBC) for protection from thermal stress and hot corrosion attack. Generally, TBC consists of two layers a ceramic top coat and a metallic bond coat on a metallic substrate. As the pure ceramic coating has very low thermal conductivity, there is a huge mismatch of coefficient of thermal expansion (CTE) between the metallic bond coat and ceramic top coat. The functionally graded coating might be helpful for alleviating the residual stress due to CTE mismatch in the coating. The functionally graded TBC refers to the layered structure of the coating, which results in a gradual change in the coefficient of thermal expansion between the constituents of the coating and the substrate. Therefore the life of the engine parts with TBC can be increased to a great extent. In generally, TBC can be achieved by plasma spraying technique. The microstructure obtained by that is splat type which is subjected to a parallel crack formation to the surface. It is more prone to delamination of the TBC from the metallic parts. Therefore in this project, the Bond Coat part of TBC will be attempted to deposit on superalloy parts by Laser Cladding based on LAM.

Research Objective

1. Selection of Bond coat material for deposition.

2. Selection of optimized parameter for laser cladding of the bond coat.

3. Modify the bond coat for greater high temperature oxidation resistance and corrosion resistance.

4. To development of top coat on optimized bond coat and performances evaluation.