Numerical Simulation And Experiment Of Heat Transfer Of Zirconia Thermal Barrier Coating Under Electron Beam

Atmospheric plasma spraying is the mainstream production process in preparation of zirconia thermal barrier coatings.It has the advantages of high production efficiency,excellent coatings quality and low cost.At the same time,the coatings has high porosity,low density and short service time defects.The high temperature heat flow or other corrosive media to corrode the metal material through the pores,result in the coating insulation failure,and even cause the coating to fall off in the course of service.In this paper,the heat transfer model of zirconia thermal barrier coatings prepared by atmospheric pressure plasma was simulated and the re-melting experiment was carried out to realize the hole sealing treatment of the coatings.The preliminary results show that:With the e-beam,zirconia coatings temperature distribution and re-melted depth depend on the electron beam power density and time.When the power density was between0.8-1.4 GW/m²?9-10.5MW/m²,the corresponding time was 200?s and 100 ms,the simulated results showed that the surface temperature of the coatings increased with the increase of the power density.The maximum longitudinal temperature gradient of 50?m thickness was 2.0 × 10⁵ K / cm and 1.9× 10⁵ K / cm,respectively,the maximum re-melted depth is 80?m and 83?m.When the power density was 1.4GW / m² and 10.5MW / m²,the corresponding surface time was 50-200?s and 30-100 ms.The surface temperature of coatings increased with time.The test results of main properties of yttria-stabilized zirconia thermal barrier coatings?YSZ coatings?by different spraying power were show the optimum process parameters to prepare the coating.The YSZ coatings were re-melted by strong current pulsed e-beam?3.8 GW / m²,pulse time 200?s,pulse number 50?,scanning e-beam?25 MW / m²,100ms?and tested the properties.After the electron beam re-melted treatment,the zirconia thermal barrier coatings pores were almost completely disappeared,the porosity was reduced by 50-80% and the lowest was only 2.59%,the hole sealing process was remarkable.X-ray diffraction analysis showed that the zirconia thermal barrier coatings was deoxidized and nitrided in high temperature,formed the black Zr₂ON₂.The micro-hardness of coatings increased by 26%-57%.In the experiment of sand blowing,the abrasion resistance of re-melted coatings increased by 33%-560%.The performance of the zirconia coatings after re-melting has been significantly improved.