Research On Wear Properties Of Composite Ceramic Coatings And Its Influence On Boiler Thermodynamic Performance

The high temperature corrosion and slagging on the heating surface of coal-fired boiler have always been the major reasons affecting the safety and economy of the boiler.Aimed at the problems,a new type of composite ceramic coating was prepared and used on the surface of heated side by slurry method.The previous researchers tested the high temperature corrosion and slagging resistance of this coating and achieved satisfied results.But the poor abrasive-wear resistance and short service life of the coating were found in the practical application.Based on the previous research,the coating was modified to improve the abrasive-wear resistance in this article.Firstly,the slurry method was used to prepare the composite ceramic coating which is mainly made of hexa-boron nitride.The microstructure of the coating and the boundary between the coating and substrate were observed by SEM.The results showed that the surface of composite ceramic coating is uniform and compact,and there are no defects such as large pores and cracks.There is also no crack at the boundary of the substrate and the coating.They are closely chimeric and have a good combination.Subsequently,in order to improve the abrasive-wear resistance of the coating,the research added respectively potash water glass and different wear-resisting particles on the basis of the original coating formula.The results of abrasion test showed that the addition of different proportions of potash water glass and wear-resisting particles can improve the abrasive-wear resistance of the original coating at 600?.Specifically,the research added 1%?mass percentage?potash water glass,1%MgO,1%ZrO₂,4%spodumene and 1%glass beads in the original coating to prepare different new coatings.The rate of wear weight loss decreases by 31%,33%,39%,38%and 30%compared with the original coating.Then the thermal shock performance and high-temperature oxidation resistance of new coatings were tested.The results showed that the numbers of thermal shock of new coatings increase 2,7,12,2,4 times and the rate of oxidation increase decreases by 9%,31%,14%,13%,48%compared with the original coating.Through the comprehensive comparison,it was concluded that the 1%ZrO₂ is the best additive for original coating.Then the emissivity of the substrate and the new coating with 1%ZrO₂ were tested in order that the parameters for the thermal calculation could be provided.The results showed that the emissivity of coating is 0.92,while the substrate is 0.73.It was concluded that the coating has a better ability of thermal radiation heat transfer.Finally,to solve the problem of slagging in a 260t/h boiler,this paper designed the spray plan and used the Fluent simulation software to simulate the furnace conditions in the working condition of 240t/h for determining the spray area.Then the actual thermal parameters of the boiler before and after spraying coating were compared.The results showed that the slagging conditions on the surface of the water-cooled wall are improved after spraying the composite ceramic coating.The furnace cutlet gas temperature,attemperating water and NO_x are both decrease.