Wear Resistant Composite Coatings Prepared By Laser Cladding On Ti-6Al-4V

Titanium alloy has the characteristics of high specific strength and good corrosion resistance.It is widely used in spacecraft,aircraft and ship’s fuselage.But the defects of titanium alloy,such as low hardness and poor wear resistance,have seriously affected the service life of titanium alloy and restrict the application and development of titanium alloy.Laser cladding technology can significantly improve the surface properties of titanium alloys,and is one of the important research directions of titanium alloy surface modification technology.Wear resistant composite coatings were prepared on the Ti-6A1-4V substrate by adding different proportions of BN+TC4+Ni powder.The effects of process parameters on the forming and micro structure of cladding layer were studied,and the effects of different powder proportioning and pulse frequency on the forming,microstructure and properties of the cladding layer were also discussed.The phase composition,microstructure and microstructure of the cladding layer were analyzed by means of X ray diffraction analyzer,scanning electron microscope and energy dispersive spectrometer.The hardness and wear properties of the deposited layer were studied by using Vivtorinox hardness tester,room temperature and high temperature wear tester.The test results show that the cladding layer is metallurgical bonded with the substrate without obvious defects.The main enhanced phase in the cladding layer is TiN.With the increase of BN content from 10wt.%to 25wt.%,the amount of TiN generated in the cladding layer is increased,and the microhardness and wear resistance of the cladding layer are obviously improved.When the addition of BN increased by more than 30wt.%,the cladding layer had obvious cracks and wear properties.The friction coefficient of the cladding layer decreases with the increase of BN addition ratio,and the friction coefficient is smaller than that of the matrix In high temperature wear samples,the wear resistance of cladding layer is mainly due to the fact that the hard reinforcement phase hinders the generation and development of cracks,and the lamellar shedding of the cladding layer is reduced.Under high load,the wear performance of cladding layer is mainly due to the support of hard reinforced phase,which prevents the grinding ball from pressing in and the surface furrow becomes shallower.In the pulse mode,the laser has obvious stirring effect on the molten pool.The micro structure of the cladding layer is uniform,and the particles of the reinforced phase are refined and dispersed,and the amount of the reinforcing phase is increased.The larger the pulse frequency is,the more obvious the stirring effect is on the cladding layer.The higher the microhardness of the cladding layer is,the stronger the wear resistance is,When the temperature is 25 and the load is 5N,the wear resistance of the cladding layer is 6 times that of the substrate.