Study On Deposition Rules Of Ti Particles And Properties Of Ti Coatings Under Low Temperature Supersonic Flame Jet

With the characteristics of high strength and excellent corrosion resistance, titanium hasbeen widely used in various fields of national economy. However, its popularization andapplication have been limited by its high cost. Low Temperature High Velocity OxygenFule(LT-HVOF) can avoid titanium from being oxidized in the spraying process and bringcompacted coating simultaneously. It provides guidance and reference for spraying Ticoatings under atmospheric conditions through studying and exploring the connectionbetween the coating properties and the deposition rules of Ti particles under low temperaturesupersonic flame jet.In this paper, Ti particles and coatings were deposited on the surface of the316Lstainless steel by LT-HVOF. The morphology of splats and properties of Ti coatings werecharacterized by optical metallographic microscope(OM), scanning electronic microscopy(SEM), X-ray diffraction(XRD), energy dispersive spectroscopy, etc. In addition, the processof particle collision substrate was simulated by nonlinearity display dynamic finite elementanalysis software ANSYS/LS-DYNA. The results were as bellows:(1) In the process of LT-HVOF, the particles deposited on the surface of the substratewere mainly in solid form, a primitive spherical particle changed into a flat one and anobvious metal jet appeared on the edge of the particle. The flatting of particles firstlyincreased and then decreased with the increasing of the spray distance. It reached itsmaximum when the spray distance was150mm. The higher the combustion chamber pressure,the greater the flatting of particles. The hardness of the substrate material and the surfaceroughness of the substrate have a great influence on the particles. The higher the hardness ofthe substrate material, the greater the extent of deformation of the particles. The rougher thesubstrate surface, the more irregular the deformation of particles, and the more obvious jets ofthe particles. The oxidation degree of particles increased when the flying distance increased.The larger combustion chamber pressure, the lower the oxygen content of the particles.(2) The surface roughness and porosity of Ti coating firstly increased and then decreasedwith spray distance increasing. The surface roughness and porosity of the coating reached itshighest productivity when the spray distance was150mm. The greater the combustionchamber pressure, the lower the surface roughness and porosity of the coating. The obviousoxidation didn’t occur at the titanium coating of LT-HVOF, and the oxygen content of thecoating was mainly based on the oxidation in the course of deposition when the spray distancewas less than170mm. It was mainly based on the oxidation during the course of the flight when the spray distance exceeds170mm. The oxygen content of the coating reduced with theenlargement of the combustion chamber pressure.(3) With the initial velocity and temperature of particles increasing, the flat ratio and thecompression ratio increased which make a better bonding between the particles and thesubstrate. While the larger the substrate hardness, the more the deformation of titaniumparticles, and the smaller the deformation of the substrate, as well as the shallower theparticles embedded into the substrate. And the surface dent depth of the substrate formed byparticles impaction increased when the substrate preheating temperature rised.