Effect Of Electron Beam Remelting Treatments On The Performances Of Plasma Sprayed Thermal Barrier Coatings And Tungsten Coatings

Plasma sprayed technology has become the most commonly used method for coatings preparation due to its high deposition rate,high production efficiency,and wide range of applications.However,the plasma sprayed coating also has obvious disadvantages.The main problem is that the microstructure of the coating is uneven,and the porosity is too high,including a lot of pores and cracks.These pores and cracks could seriously affect performances of the coatings,and reduce the service life of the coatings.Electron beam remelting treatments have the advantages of high energy utilization rate,simple and reliable production equipment,and no pollution in the process.Therefore,this technology can effectively reduce the porosity of coatings and improve performances of the coating.Especially used for high melting point coatings remelting,high-power electron beam devices have unique advantages.In this paper,the most representative high-melting point material coatings in thermal barrier coating materials and metal materials were selected: the zirconia coating and the tungsten coating are respectively research by using electron beam remelting treatments.Zirconia coatings are widely used in thermal barrier coatings for hot end components in aerospace engines.Tungsten coatings are mainly used in plasma facing materials in nuclear fusion devices.These materials of coatings have common issues,such as poor corrosion resisting property and poor thermal shock resistance caused by high porosity of the coating.And these problem could significantly short service life.The electron beam remelting treatments can effectively solve the above problems and improve the performances of the coatings.Comsol Multiphysics software was first used to simulate the temperature field of zirconia coatings and tungsten coatings respectively.In order to provide theoretical basis to experiments research,the effects of external heat source parameters including powers and acting time on the temperature field simulationgs of the coatings were studied.In the experiments,zirconia coating and tungsten coatings were respectively prepared by plasma sprayed technology,and then electron beam remelting treatments were performed on the coatings surface.After that,the performaces of coatings including microstructure,porosity,microhardness and thermal shock resistance before and after remelting treatments were examined.The results showed that the simulation results of the temperature field were basically consistent with the results of experiments.The properties of the zirconia coatings and the tungsten coatingsafter electron beam remelting have been significantly improved: After treatments,the microstructure of the coatings changes from lamellar structure to a compact remelted layer composed of columnar structure on the top of the surface,and the remelted depth is about 40-60?m.Monoclinic phase was disapeared,porosity reduced nearly 20%,roughness of surface reduced significantly,and microhardness also has nearly doubled.The wear behaviours and thermal shock resistance were significantly improved.As for tungsten coatings,Content of oxygen has reduced and purity of tungsten has improved after remelting.The electron beam treatments of spryaed tungsten coaitngs generated a compact remelted layer on top of the surface composed of columnar structure.The remelted depth is about 30?m.Porosity has reduced nearly15%,Microhardness has also increased 1.8 times.