Experimental Research On Laser Cleaning Of Anticorrosive Coatings For Oil And Gas Pipelines

Laser cleaning technology uses pulsed laser to irradiate the surface of the object to be cleaned.Through the interaction of the laser and the object,the structure and composition of the object itself change,leading to changes in the macro-mechanical properties between the object and the substrate,and ultimately achieve the purpose of cleaning.This technology has the advantages of extremely high cleaning efficiency and cleaning accuracy,and is harmless to the environment and people.It is currently widely used in the aviation industry,microelectronics,and cultural relics restoration,but the laser cleaning of oil and gas pipeline coatings is basically a blank;In order to find a technology to replace the traditional coating method of cleaning oil and gas pipelines,it is necessary to explore the best parameters of laser cleaning for oil and gas pipeline anticorrosive coatings,analyze the cleaning mechanism,and study the effect of laser parameters on cleaning quality.The development of the cleaning experiment requires parameter guidance.First,establish a laser cleaning oil and gas pipeline coating model,and establish the energy conservation equation and temperature distribution equation for the cleaning model with the laser and style used in the experiment;Secondly,prepare the samples used in the experiment and test the coating composition and the adhesion between the coating and the substrate;Finally,group and single-variable experiments are carried out on the patterns with different substrate roughness,and the influence of varying the number of laser scans and the roughness of different substrates on the removal effect of the coating is studied;Summarize and analyze the special morphology that appears in all cleaning experiments.Under the premise of removing the complete coating,perform cleaning experiments with variable laser power and scanning speed to study the corrosion resistance of the substrate surface and the initial substrate corrosion resistance.Changes affect the mechanical properties of the surface and cross-section of the substrate.Through the variable power simulation laser cleaning experiment,the cleaning threshold is 20 W,and the substrate damage threshold is 400 W.The adhesion test results show that the adhesion between the coating and the substrate decreases as the roughness decreases;The integrated analysis of the data after the cleaning experiment found that under certain other parameters,the more scan times,the greater the cleaning rate;Under the same laser cleaning parameters,the lower the roughness,the higher the coating removal rate,but too low roughness will cause excessive oxidation of the substrate surface.Increasing power will reduce the number of scans to complete the coating removal task,and will also increase the degree of oxidation of the substrate surface.Through the three-dimensional topography test,it is found that laser cleaning will change the surface topography of the substrate to form a peak and valley structure.As the injected laser energy increases,the surface roughness of the substrate decreases;the average distance between peaks and valleys of the profile is positively correlated with the laser power;the greater the power,the greater the temperature of the substrate,the deeper the profile groove formed under the impact of the laser.Under the experimental conditions used in this study,42.5W is the best laser power;as the speed increases,the number of scans to complete the target will increase,but the oxidation degree of the substrate surface will decrease,and 2500mm/s is the best scanning speed;Then,through the analysis of the microstructure of the cross-section of the cleaned substrate,it was found that the cross-section of the substrate showed new morphologies: banded areas and cracks existed areas.The reason was that the small holes of the substrate itself had element oxidation around them.Gasification causes the original element to be unbalanced.The small holes are first torn to form cracks.The continuous injection of heat makes the cracks gradually connect together and combine with laser shock extrusion to form a ribbon.The entire cleaning experiment shows that appropriate laser cleaning parameters will meet the purpose of removing the coating and improve the hardness and corrosion resistance of the substrate surface.