Numerical Simulation And Experimental Investigation On Laser Cladding TiB Particles Reinforced Titanium Alloy

Titanium alloy(TC4)is widely used in aerospace,machinery and chemical industry as well as medical field due to its good specific strength,corrosion resistance and oxidation resistance.However,because of its low hardness and poor wear resistance,the value of titanium alloy is reduced.In order to solve these problems,the composite coating of titanium alloy was prepared by laser cladding in this paper.The finite element software was employed to analyze the temperature field and melt flow,the Ti/TiB composite coating of TC4 was successfully obtained,the morphology of the cladding layer was observed,the microstructure of the laser cladding was analyzed,the microhardness and friction and wear properties of the coating were tested.The main conclusions were as follows:(1)The temperature field and the temperature change were analyzed under different process parameters.The cooling rate of the molten pool was discussed.The results were as follows: the temperature contour plots of top surface was seen to be elliptical.The temperature increased with laser power increasing and decreased with the increase of scanning speed.Compared with laser power,the influence of scanning speed on temperature evolution was much smaller than that of laser power.As the scanning speed increased,the cooling rate decreased with constant laser power.With the increasing of the pool depth,the cooling rate and the gradient increased.(2)The characteristics of flow field and the velocity changes under different laser process parameters were discussed.The conclusions were as follows: With the effect of Marangoni convection,the melt flow of the molten pool surface was radial outward,forming two opposite vortex loops,which caused the phenomenon of strange double peaks on the surface.That was,the edge of molten pool had the maximum velocity,while the center obtained the minimum value.With increasing laser power,the velocity of liquid in the molten pool increased.However,with the increase of scanning speed,the velocity of liquid in the molten pool decreased.The influence of laser power on the flow field of molten pool was greater than that of scanning speed on the flow field.(3)The experiments of laser cladding Ti/TiB on the surface of titanium alloy under different processing parameters were carried out.The results showed the surface morphology of the cladding layer was good under the laser power of 2500 W power and the scanning speed of 8 mm/s;the cladding layer was composed of fiber structure,white particles,block structure and other structures.While the scanning speed kept constant,with the increase of the laser power,the microstructure of the cladding layer became finer,the microhardness increased.However,the microhardness decreased with increasing scanning speed when laser power was fixed.When scanning speed was fixed,the friction coefficient value was smaller with the increase of laser power.When laser power was fixed,the friction coefficient value was larger with the increase of scanning speed.The wear mechanism of cladding layer was mainly ploughing wear,adhesion wear and oxidation wear.