不同激光参数下ZrO2陶瓷涂层激光烧蚀损伤行为OA

ZrO2 ceramic coatings have emerged as a primary choice for laser protection due to their exceptional thermal stability,high melting point,low thermal conductivity,and phase transformation toughening characteristics.The unique high-temperature phase behavior of ZrO2 not only facilitates significant heat absorption during laser irradiation but also mitigates thermal stress and suppresses crack propagation through volume changes associated with its phase transformations.Furthermore,the relatively good thermal expansion match between ZrO2 coatings and metallic substrates enhances the reliability of the protective structure by reducing interfacial thermal stresses.Focusing on ZrO2 ceramic coatings,the work aims to investigate their ablation resistance and protective performance under various laser parameters.The ZrO2 ceramic coating was fabricated with the atmospheric plasma spraying(APS)technique.The substrate material was an aluminum alloy disk with a diameter of 80 mm and a thickness of 5 mm.Prior to coating deposition,the aluminum alloy substrate underwent surface preparation involving blasting with sand(e.g.,white corundum)to enhance roughness and adhesion,followed by ultrasonic cleaning in absolute ethanol and drying.Laser ablation experiments were conducted through a self-built experimental platform equipped with a continuous-wave laser source.The material was ablated under different laser powers(2,5,8 kW)and spot diameters(3,4.5,6 cm),systematically evaluating the protective performance of the ZrO2 coating under these parameters.For specific parameter sets,a thermocouple was positioned at the center of the sample's back surface to monitor the temperature evolution in real time.Post-irradiation analysis involved comprehensive characterization of the coatings.Spectral reflectivity was measured with a spectrophotometer,phase structure was analyzed by X-ray diffraction(XRD),and damage morphology before and after ablation was examined through scanning electron microscopy(SEM)and optical microscopy.These techniques contributed to understanding the coating's reflective properties,phase stability under thermal load,and failure mechanisms.Results indicated that the ZrO2 coating exhibited a high reflectivity(R)of approximately 97%,with a laser coupling coefficient(ε)of 3%.This represented a 79%reduction compared to the coupling coefficient of the aluminum alloy substrate(14%).Phase analysis revealed that the crystal structure of the ZrO2 coating transitioned from the tetragonal phase to the cubic phase following laser ablation.The extent of coating damage intensified with the increasing laser power and the decreasing spot diameter.After laser ablation,the affected area of the ZrO2 coating was divided into three distinct zones:the unaffected zone,the slightly affected zone,and the highly affected zone.The slightly affected zone maintained a relatively smooth surface with clearly defined and well-connected grain boundaries.In contrast,the highly affected zone was characterized by the presence of extensive cracks and a mixture of fully melted and partially melted regions.When subjected to laser irradiation,the central region of the ZrO2 ceramic reached its melting point and formed a molten pool.The material subsequently entered both molten and vaporized states,leading to material splashing and ablation damage.Under continuous laser action,plasma was induced,while the bottom of the molten pool gradually transformed into a recast layer.After the laser irradiation ceased,thermal stress generated during the cooling of the molten pool resulted in the formation of microcracks on the surface of the ablation crater.