Adjustment of experimental parameters of laser drilling for reducing delimination length of thermal barrier coating on superalloys

Abstract

Temperatures in the high-pressure chamber of aircraft engines are continuously increasing to improve the engine efficiency. As a result, constitutive materials such as cobalt and nickel-base superalloys need to be thermally protected with zirconium oxide coating. The laser drilling process is used to realize thousands holes at acute angles in the combustion chamber made with this coating material. Laser percussion drilling is a well-established industrial process from decades; however several fundamental questions are still unsolved about the physical understanding of the laser matter interaction, moreover when the target drilled is composed with several materials. Each hole drilled by laser present some defaults, which is crucial to reduce to increase the part lifetime and engine efficiency. In the specific case of hole drilled in TBC at acute angle, the two main defaults are the length of an interfacial cracking (also called delimitation length) and the recast layer thickness in the metal part of the sample. The present work aims at characterizing interfacial cracking induced by laser drilling on coated cobalt-base super alloy. In this paper, we show what is the physical mechanism leading to the delimitation crack and how to reduce the delamination length by 72% and the recast layer thickness by 4, fitting laser parameters.Temperatures in the high-pressure chamber of aircraft engines are continuously increasing to improve the engine efficiency. As a result, constitutive materials such as cobalt and nickel-base superalloys need to be thermally protected with zirconium oxide coating. The laser drilling process is used to realize thousands holes at acute angles in the combustion chamber made with this coating material. Laser percussion drilling is a well-established industrial process from decades; however several fundamental questions are still unsolved about the physical understanding of the laser matter interaction, moreover when the target drilled is composed with several materials. Each hole drilled by laser present some defaults, which is crucial to reduce to increase the part lifetime and engine efficiency. In the specific case of hole drilled in TBC at acute angle, the two main defaults are the length of an interfacial cracking (also called delimitation length) and the recast layer thickness in the metal part of the sa...