Investigations on the water-jet guided laser scribing of thermal barrier coated IC21 nickel-based superalloy

Abstract

Ceramic thermal barrier coatings (TBCs) are widely recognized as state-of-the-art for ensuring the stability and reliability of turbine blades operating in extreme conditions. However, the significant disparities between the thermal and mechanical properties of TBCs, bonding layers (BCs), and nickel-based superalloy substrates pose considerable challenges for machining film cooling structures on turbine blades while minimizing coating delamination, heat-affected zones (HAZs), and other potential defects. The utilization of Water-Jet Guided Laser (WJGL) has gained significant attention as a promising approach for the machining of advanced materials, including ceramics and multi-layer composites. In this study, a theoretical model is proposed to describe the transient interaction between WJGL and TBC IC21 nickel-based superalloy. A numerical simulation using the deformation geometry method is employed to investigate the evolution of ablation morphology, which is further validated by experimental data. Specifically, the formation mechanism of the shoulder structure at the material interface is explained. Furthermore, orthogonal experiments are conducted to establish the fundamental influence rule and significance level of machining parameters on the microscopic groove morphology. Based on these findings, multi-row cutting experiments are performed to identify the optimized scanning trajectory for achieving the high-quality thorough cutting of the substrate with a thickness of 2.7 mm, while minimizing oxidation, residue deposition, and delamination. The outcomes of this study contribute to the knowledge of WJGL machining, and could potentially improve the efficiency and accuracy of advanced material processing techniques.