Regularity Analysis of Laser Cleaning of Carbon Steel Corrosion Layers and Reasonable Depth Prediction of Non-Destructive Substrates University

Abstract

A continuous fiber laser with medium and low power was used to clean the corrosion layer on the surface of severely corroded steel parts. The depth of corrosion layer removal, surface roughness and chemical composition were analysed by laser confocal microscopy and scanning electron microscopy-energy dispersive X-ray spectrometry, and the microhardness of the sample surfaces was determined by microhardness tester. The removal mechanism was analysed by numerical calculations, and prediction equations for the values of non-destructive substrate cleaning power corresponding to different thicknesses of the rust layer were derived by numerical calculations. The occurrence of fused condensation layer and heat affected zone was found in the cross section. Both experiments and numerical calculations together illustrate that the removal of the corrosion layer on the surface of the steel parts is removed by vaporization and thermal ablation behaviour. The experiments showed that the corrosion layer was completely removed when the power density reached 3821W/mm2. In contrast to the previous cleaning, the surface hardness increased to a maximum at a power density of 4204W/mm2 due to the formation of a reinforcing oxide layer on the cleaned surface. By numerical calculations to establish a prediction of the rust removal equation without damage to the substrate, the thickness of the corrosion layer and the laser power showed a nonlinear increase in the relationship. As for roughness, the laser power density shows a nonlinear trend of roughness, which is first decreasing and then increasing. A new parameter "line energy" is proposed for laser cleaning, and the relationship equation between "line energy" and roughness is established. "Line energy" at 420J/mm3 corresponds to the lowest value of roughness 0.7µm.

Keywords: Laser cleaning, corrosion layer, Surface roughness, thermal ablation；line energy