| The substation grounding network is an important facility to ensure the safe and stable operation of the power system.But it is easy to be corrosing by soil p H,water content,resistivity,salt,microbial and other factor.In the condition of grounding grid`s corrosive defects,short-circuit current or lightning impulse current will lead to the ground potential and step potential increases around the grounding device,which constitutes a huge threat of personnel safety and stability of system.At present,the domestic and foreign experts and scholars believe that the choice and improvement of grounding materials are the most fundamental and important solution on grounding corrosion,and they focus their energy on studing stainless steel,copper clad steel,alloy coating and conductive anti-corrosion coatings and other new grounding materials,But less work on the application of metal ceramic coating in the grounding network.In this paper,the experimental investigation of the application of the metal ceramic coating in the grounding grid was carried out.The WCCo and Ti N powder coatings with different parameters were prepared by supersonic flame spraying respectively.In order to solve the defect of the coating,the preparation method was improved.The multi-arc ion plating process was used to prepare Ti N and Ti-Si-N coatings,and their coating properties were compared.The better Ti-Si-N cermet coating was further studied and analyzed.The main work is as follows:(1)Two kinds of different materials(WC-Co and TiN),two powder feed voltages(4.5V and 6V),and four kinds of coating layers(3,6,9 and 12)were prepared using supersonic flame spraying technology.Layer,and introduced the main equipment and preparation technology process flow of supersonic flame spraying.The four-pole method was used to test the electrical properties of the various parameters of the coating.The salt spray test was compared with the existing Q235 primary steel and galvanized steel for corrosion resistance.The results show that the resistivity of the cermet coating prepared by the thermal spraying process can meet the requirements of the grounding body’s dispersion,but its corrosion resistance is poor compared with the galvanized steel.(2)Scanning electron microscopy(SEM)was used to study the microstructure and composition of the plane and cross-section of the coating to investigate the reasons for the poor corrosion resistance of the cermet coating prepared by supersonic flame spraying.Results Surface: Both cermet coating surfaces contained large visible bubbles and crevices and did not completely cover the substrate;The two coatings are not evenly distributed in cross-section,and are thin and thick,and some even produce fractures.Crevices and fractures reduce the density of the coating and cause it to corrode.(3)In order to solve the existence of corrosion holes in the coating prepared by the thermal spraying method and to improve the preparation process,the multi-arc ion plating method was used to prepare the cermet coating,and the Ti N and Ti-Si-N coating samples were used for electrical performance and corrosion protection.Performance comparison.The results show that the electrical properties of the cermet coating prepared by multi-arc ion plating meet practical requirements,and its corrosion resistance is Ti-Si-N coated workpiece> galvanized steel> Ti N coated workpiece.(4)In this paper,the multi-arc Ion-plated Ti-Si-N coating with the best corrosion resistance is selected to study the control process.Scanning electron microscopy(SEM)is used to investigate the microscopic changes in the plane and cross-section of the coating under different negative pulse biases,and this parameter is analyzed.The effect on the nature of the coating was chosen to select the best preparation method for the grounding material.The results show that when the negative pulse bias voltage is set to-150 V,the surface of the coating is uniform and the cross-sectional thickness is uniform,which is the best setting. |
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