Laser Removal of Coating on Oil and Gas Pipelines: Effects on Microstructure and Hardness of Substrate

To study the feasibility of laser exfoliation of the external coating of oil and gas pipelines and the effects of coating removal on the properties of the substrate, laser coating removal experiments were conducted on the epoxy resin coating on the X65 pipeline steel using a short-pulse laser. After coating removal, the pipe external surfaces were tested using a three-dimensional morphology tester. The surface and cross-section of each sample were tested and analyzed using scanning electron microscopy and energy spectrum analysis. After the two samples were irradiated using different laser technical parameters, the coating layers were almost completely exfoliated. At the same time, dense crater morphology was evident on the surface and strip-shaped and crack regions appeared below the surface. The strip-shaped regions beneath the surface were about 20 pm. and 10 pm thick for samples A and B, respectively, while the crack regions were about 100 mu m. and 90 mu m thick, respectively, and the hardness of both the samples' surfaces increased slightly. The laser technical parameters used in this research not only meet the requirements of laser coating removal for steel pipes but also strengthen the surface. Thus, coating removal is technologically feasible for steel pipelines and valuable for further investigation.