Effect Of Heat Treatment And Spray Parameters On Properties Of The Ti-6Al-4V Coating By Low Pressure Plasma Spraying

Titanium alloy has the advantages of low density,high specific strength,heat resistance and corrosion resistance,and is widely used in cutting-edge fields and civil applications.Ti6Al4V alloy is the alloy with.the largest amount of titanium alloy due to its good comprehensive properties.Traditional titanium alloy parts are mainly made casting and forging,but because titanium alloys are easily oxidized,these two processes need to be carried out in a protective atmosphere.In recent years,the injection molding of titanium alloy parts has attracted the attention of researchers.The cost of atomized spherical powder commonly used in spraying is relatively high.The cost of hydrodehydrogenation(HDH)Ti6A14V powder is about 1/10 of the spherical powder,but there is no research on this method.In this study,low-pressure plasma equipment and 150 mesh and 325 mesh powders was used to deposit Ti6A14V coating.with different the spraying parameters.The effects of spraying parameters.and powder size on the coating structure and performance were studied.Subsequently,the coating was vacuum heat treated with a vacuum furnace at different heat treatment temperatures.The effect of heat treatment temperature on the evolution of the coating structure and coating properties was studied.Use scanning electron microscope(SEM),X-ray diffraction(XRD),energy dispersive spectrometer(EDS),hardness tester and other equipment to test the structure,mechanical properties and element distribution of the coating,and use XRD to scan slowly to calculate the lattice constant c of the coating The value of c/a.The results show that:by adjusting the spraying parameters,a coating with good performance and low porosity can be prepared,and the density of the coating is almost 100%.The larger powder size has a smaller specific surface area,which can reduce the oxidation of the powder during the spraying process,and the prepared coating has better fracture toughness.After heat treatment,the coating will undergo recrystallization and grain growth,forming an equiaxed structure.The grain size of the equiaxed crystals formed by the heat treatment of the 150 mesh powder coating is larger.During the heat treatment,elements such as Al and V are redistributed,and the V element is precipitated from the equiaxed grains,forming a granular ? phase at the equiaxed grain boundaries.The increase of heat treatment temperature will promote the solid solution of oxygen atoms and titanium alloy.The amount of solid solution of oxygen will affect the value of the lattice constant c/a of the titanium alloy.With the increase of the heat treatment temperature,the solid solution content of oxygen increases,and the value of the lattice constant c/a increases.Oxygen element forms interstitial solid solution with titanium alloy during heat treatment,causing lattice distortion,which makes the hardness of the coating increase with the increase of heat treatment temperature.The solid solution of oxygen will also reduce the fracture toughness of the coating and make the coating brittle.