Preparation And Research Of Microstructures And Properties About Wc Based Coating On The Surface Of TC4 Titanium Alloy

TC4 is widely used in aerospace structures parts,because of its high specific strength and high specific modulus.However,the low hardness and poor wear resistance of titanium alloy reduce the service life,and limit the full play of its potential.In this paper,WC-12Co and WC-10Co-4Cr coatings were prepared by plasma spraying and laser remelting technology.The effects of plasma spraying and laser cladding on the microstructure and wear resistance,corrosion resistance and thermal shock resistance of the two kinds of coatings were studied.The experimental results of plasma spraying show that the WC-based coating prepared by plasma spraying is the layered structure of WC phase.There is a certain amount of pores,no melted and semi melted particles in the coating.The coating mechanically combined with the substrate.With the increase of power,the pore size and quantity and the powder decrease,and the average hardness increased.When the power is 28kW,the hardness of WC-12Co coatings is 904 HV_0.3 and the hardness of WC-10Co-4Cr coating is898 HV_0.3,the hardness is equal.But the WC-10Co-4Cr coating is more compact,the hardness is less dispersed,and the thermal shock resistance is better than that of WC-12Co coating.The results of laser remelting show that two kinds of coatings were remelted by laser,and the layer structure of plasma spraying was eliminated.the dense dendritic microstructure was obtained.The powder and pore size of the coating are greatly reduced,and the density of the coating increases significantly.The metallurgical bonding between coating and substrate is realized.The hardness of the coating increased significantly,and the dispersibility of hardness decreased greatly.When the power is 600W and the scanning speed is 14 mm/s,the hardness of WC-10Co-4Cr coating is 1104.4 HV0.3?The remelting layer is compact,the fine dendrites are distributed uniformly,and the thermal shock resistance is greatly improved.The experimental results show that the wear resistance of WC-10Co-4Cr coating prepared by plasma spraying is better than that of WC-12Co coating.The wear rate of the matrix is reduced by 5.4 times,and the wear resistance of the matrix is improved significantly.After laser remelting,the wear weight loss rate is reduced to 0.38 mg/min,which is 1/12 of the corresponding coating,further improving the wear resistance.The electrochemical experiments show that the corrosion resistance of WC-10Co-4Cr coating is significantly better than that of WC-12co coating under the optimized process parameters.The electrode potential of the sprayed ceramic coating was increased by 291mV,and the corrosion current reduced 0.055 mA.After laser remelting,the corrosion potential increased by 504 mV,the corrosion current decreased by 0.056 mA,and the corrosion resistance was further improved.The coating prepared by plasma spraying and laser remelting technology shows that the hardness and wear resistance of the coating are improved by plasma spraying,but the porosity is much and the bonding strength is poor.The laser remelting can eliminate the porosity of the coating,improve the bonding strength,make the coating more compact and more stable,and further improve the hardness and wear resistance of the matrix.