Laser powder deposition of thin-walled mesh structure for longevity of thermal barrier coating

Abstract

Laser powder deposition (LPD) provides a flexible and efficient way to manufacture thin-walled structures in a precise way. Our current in-situ LPD system enables the following manufacturing capability - 450 µm track thickness and 70 µm track height at minimum. Thin-walled mesh made of Inconel 718 or MCrAlY were first deposited on Hastelloy substrates using LPD technique, and then coated with thermal barrier coatings (TBC). It was found that the TBC systems with mesh structure showed a much longer lifetime. This is attributed to the existence of the mesh structure, which inhibits the propagation of cracks as well as enhances the bond strength between the TBC coating and substrate. However, the mesh structure also introduces local stress concentration at the peak of the mesh, which serves as a weak point for crack nucleation. Finite element method (FEM) was used to simulate the stress distribution of TBCs. In addition, the effects of mesh dimension and morphology on residual stresses were investigated. It is revealed that mesh structures with low curvature and low aspect ratio could lead to a longer thermal cycling life.Laser powder deposition (LPD) provides a flexible and efficient way to manufacture thin-walled structures in a precise way. Our current in-situ LPD system enables the following manufacturing capability - 450 µm track thickness and 70 µm track height at minimum. Thin-walled mesh made of Inconel 718 or MCrAlY were first deposited on Hastelloy substrates using LPD technique, and then coated with thermal barrier coatings (TBC). It was found that the TBC systems with mesh structure showed a much longer lifetime. This is attributed to the existence of the mesh structure, which inhibits the propagation of cracks as well as enhances the bond strength between the TBC coating and substrate. However, the mesh structure also introduces local stress concentration at the peak of the mesh, which serves as a weak point for crack nucleation. Finite element method (FEM) was used to simulate the stress distribution of TBCs. In addition, the effects of mesh dimension and morphology on residual stresses were investigated. It ...