Simulation and experimental study of femtosecond laser ablation mechanisms of NiCoCrAlY coatings

• Published in: Surface & coatings technology 2024-10, Vol.494, p.131469, Article 131469
• Main Authors: Hu, Yue, Jiang, Ruisong, Huang, Chongxiang, Chen, Chaolang, Wang, Shaojian
• Format: Article
• Language: English
• Subjects: Femtosecond lasers; NiCoCrAlY bond coat; Numerical simulation; Thermal accumulation effects; Turbine blade thermal barrier coating; Two-temperature model
• ISSN: 0257-8972
• DOI: 10.1016/j.surfcoat.2024.131469

To enhance the adhesion of turbine blade thermal barrier coating systems using the LST method, a thorough understanding of the ablation mechanism of NiCoCrAlY bond coat material by femtosecond laser systems is essential for producing high-quality textured grooves. This study systematically investigates the ablation mechanisms of NiCoCrAlY material, exploring the effects of laser energy density, laser scanning speed, and the number of laser scans on the ablation of NiCoCrAlY. Numerical simulations based on the two-temperature model were conducted, providing a comprehensive analysis of thermal effects, heat accumulation, and material response during the laser ablation process. The experimental results indicate that 1) the ablation phenomenon caused by heat accumulation becomes evident as the laser energy density increases from 1.948 J/cm2 to 4.521 J/cm2, with the accumulated heat reaching 1525.2 K, leading to distinct melting residues and heat-affected zones on the groove walls. 2) The change in laser scanning speed also affects heat accumulation. Using a laser scanning speed of 800 mm/s results in a high material removal rate, smooth machined walls, and a uniform surface with no significant heat-affected zones. 3) Excessively high numbers of laser scans shift the laser focus to the bottom of the groove. The high concentration of laser energy causes intense localized ablation, forming sharp bases with numerous cracks and melting residues. To achieve efficient and high-quality laser ablation, it is necessary to ensure that the number of scans remains below 40. •The femtosecond laser ablation mechanism of NiCoCrAlY coating is studied for turbine blade applications for the first time.•The effect of laser ablation parameters on material removal depth and surface quality was investigated using a single factor approach.•A two-temperature model (TTM) describes energy transfer between electrons and the lattice system, with simulation results for coating ablation.•The comparative analysis results verify the superiority of the proposed method.