Variable angle laser drilling of thermal barrier coated nimonic

Kamalu, John; Byrd, P. J.; Pitman, Andrew R.

doi:10.1016/s0924-0136(02)00044-4

Cited by 54 publications

(18 citation statements)

References 5 publications

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“…Regarding the formation of these holes, laser drilling is widely used owing to its non-contact, precise, and reproducible advantages. Nevertheless, it is possible for laser drilling process to damage the vulnerable interface between bond-coat and top-coat [20,21], eventually causing the spallation. In addition, regions of the component will also be subject to the particle impact and foreign object damage, with the result of the spallation.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive damage evaluation of localized spallation of thermal barrier coatings

et al. 2017

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Thermal barrier coatings (TBCs) enable the hot section part to work at high temperatures owing to their thermal barrier effect on the base metal components. However, localized spallation in the ceramic top-coat might occur after long duration of thermal exposure or thermal cycling. To comprehensively understand the damage of the top-coat on the overall hot section part, effects of diameter and tilt angle of the spallation on the temperature redistribution of the substrate and the top-coat were investigated. The results show that the spallation diameter and tilt angle both have a significant effect on the temperature redistribution of the top-coat and the substrate. In the case of the substrate, the maximum temperature increment is located at the spallation center. Meanwhile, the surface (depth) maximum temperature increment, having nothing to do with the tilt angle, increases with the increase of the spallation diameter. In contrast, in the case of the top-coat, the maximum temperature increment was located at the sharp corner of the spallation area, and the surface (depth) maximum temperature increment increases with the increase of both the spallation diameter and the tilt angle. Based on the temperature redistribution of the substrate and the top-coat affected by the partial spallation, it is possible to evaluate the damage effect of spalled areas on the thermal capability of TBCs.

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Section: Introductionmentioning

confidence: 99%

Comprehensive damage evaluation of localized spallation of thermal barrier coatings

et al. 2017

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“…These holes are currently produced using mainly laser drilling. To increase the cooling performance, drilled parts are also coated with a thermal barrier [18]. The coated material is a thermal-refractory ceramic with a thickness around 200μm.…”

Section: Introductionmentioning

confidence: 99%

Modeling laser drilling in percussion regime using constraint natural element method

et al. 2015

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is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. Abstract The laser drilling process is the main process used in machining procedures on aeronautic engines, especially in the cooling parts. The industrial problematic is to reduce geometrical deviations of the holes and defects during manufacturing. The interaction between a laser beam and an absorbent metallic matter in the laser drilling regime involves thermal and hydrodynamical phenomenon. Their role on the drilling is not yet completely understood and a realistic simulation of the process could contribute to a better understanding of these phenomenon. The simulation of such process induces strong numerical difficulties. This work presents a physical model combined with the use of the original Constraint Natural Element Method to simulate the laser drilling. The physical model includes solid/liquid and liquid/vapor phase transformations, the liquid ejection and the convective and conductive thermal exchanges. It is the first time that all these phenomena are included in a modelling and numerically solved in a 2D axisymmmetric problem. Simulations results predict most of measurements (hole geometry, velocity of the liquid ejection and laser drilling velocity) without adjusting any parameters.

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“…However, a number of defects are inherently associated with current laser drilling systems. As mentioned previously, these include spatter, recast layer, microcracks and taper of the drilled hole, as well as delamination at the interfaces of dissimilar material layers [4,5,10,11,12,13,14]. These defects affect the metallurgical and geometrical quality and presumably limit the performance of materials.…”

Section: Discussionmentioning

confidence: 99%

“…Thermal expansion coefficient measurements in TBC-coated superalloys reveal large expansion mismatches [23]. With rapid heating, these mismatches result in the buildup of thermal stress and interface delamination with conventional lasers [4,10,13,14]. During conventional laser machining of these systems, the re-solidified ceramic layer at the side wall of the hole has been observed overlaying the bond boat and substrate, and has been found recently to have the strong effect on the debonding and crack deflecting [14].…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, a number of processing defects are encounted including spatter, remelted layers, microcracking, tapering of the drilled hole as well as the delamination of interfaces in the case of TBCs [4,5,10,11,12]. Laser-induced cracking in TBC-coated superalloys has been observed at both the bond coat/substrate and bond coat/TBC (top coat) interfaces [13,14]. Previous parametric studies revealed that the quality of drilled holes depends on material properties and the optimization of laser processing parameters, such as laser fluence, pulse duration, pulse repetition rate and pulse shape [4,12,15].…”

Section: Introductionmentioning

confidence: 99%

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Femtosecond Laser Micromachining of Single-Crystal Superalloys

Feng

Picard

Liu

et al. 2004

Superalloys 2004 (Tenth International Symposium)

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Investigations on femtosecond laser micromachining of single crystal superalloys with and without plasma-sprayed thermal barrier coatings were conducted under laser fluences ranging from 0.1 J/cm 2 up to 160 J/cm 2 . Micromachining was carried out in air using a titanium:sapphire laser system ( = 780 nm) operating at a repetition rate of 1 kHz and delivering individual pulses of ~150 fs duration. The ablation threshold of the single crystal superalloy was determined as 203 ± 20 mJ/cm 2 . Laser-induced damage was examined by means of scanning electron microscopy and transmission electron microscopy. These studies indicate a complete absence of any melting, recast layers, heat-affected zones or microcracks in the vicinity of the machining area. The only form of damage observed in the single crystal superalloy machined near or above the ablation threshold was a laser-induced plastically deformed layer with a maximum extent of ~5 m. Machining through ceramic thermal barrier coatings on a superalloy produced no delamination along the superalloy/coating interfaces or cracks within the TBC or bond coat. The residual roughness of the machined surface was in the sub-micron range. The present study suggests that femtosecond laser micromachining is a very promising technique for production of finescale features in multi-layer material systems for aerospace and power generation components.

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Variable angle laser drilling of thermal barrier coated nimonic

Cited by 54 publications

References 5 publications

Comprehensive damage evaluation of localized spallation of thermal barrier coatings

Comprehensive damage evaluation of localized spallation of thermal barrier coatings

Modeling laser drilling in percussion regime using constraint natural element method

Femtosecond Laser Micromachining of Single-Crystal Superalloys

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