Numerical calculation of temperature and surface topology during a laser ablation process for ceramic coatings

Abstract

In this paper a numerical procedure is presented to calculate a laser ablation process for ceramic thick film coatings. The code is required to cover temperature dependent material data, projected beam intensities and inhomogeneous coating-substrate combinations to calculate the hole shape geometry, the temperature distribution under the surface and the ablation rate per pulse. Therefore, the ablation speed was calculated by an Arrhenius equation while the temperature distribution was simulated by means of the heat conduction equation, which is solvable by a finite differences scheme. Hence, an adaptive mesh is used and the expansion of the code to three spatial dimensions enables the simulation of more complex ablation geometries. The simulation time was held low by introducing actualization frequencies, where critical and time consuming steps were only run if necessary. A validation of the numerical simulation was done by comparing the calculated temperature depth distribution and hole geometry with micrographs of experimental ablations.

Residual Stress Evaluation in Ceramic Coating Under Industrial Conditions by Digital Holography

“…The energy of the focused laser pulses need to be just above the threshold necessary for ablation in order to avoid the unwanted plasma production that may disturb the ablation process. On the other hand, the laser ablation creates a 2-μm deep heat affected zone on the coating [17], which is small enough to be neglected for the calculation of residual stresses with this experimental setup. Fig.…”

“…The Poisson's ratio of the ceramic coating is assumed as 0.23 [18] and the Young's modulus is estimated by indentation test [17] with a value of 166 Gpa. The material for substrate plates was aluminium (alloy 5754-H111) with sizes of 100 × 100 × 5 mm³.…”

Evaluation of Residual Stress Determinations Conducted with Laser Ablation and Optical Displacement Measurement

“…Due to the high energy densities (> 10 6 W/cm²) the subjected material sublimates almost suddenly and a high back pressure builds up which accelerates the ablated material out of the hole. As this thermodynamic process imposes heat, a numerical simulation was conducted in order to investigate possible heating effects [4]. It was shown, that the majority of heat is transported out of the specimen by the sublimation of material.…”

3D transient model to predict temperature and ablated areas during laser processing of metallic surfaces

“…14 Weidmann et al solved the 2D equation for calculating the temperature distribution and used the Arhenius equation to estimate the speed of ablation and predict the ablated zone. 15 Sinha solved the 2D equation and took phase changes into his model to predict the ablation zone. In this model the size of computational cells was decreased when their temperature exceeded boiling point to model evaporation.…”