Study On Functional Surface Preparation Of Titanium Alloys Induced By Short Pulse Width Laser And Influence Of Process Parameters

The economic losses and safety risks associated with surface ice accumulation in critical areas of aircraft are a serious impediment to the development of civil aviation.Current de-icing methods,which rely on active de-icing strategies,have many limitations on the structural design of aircraft and engines and cannot meet the increasing demand for aviation safety and economy.Therefore,surface modification of icing-prone areas based on bionic principles to make them inherently ice-resistant has become one of the most promising solutions for surface ice accumulation in the eyes of designers.There are many parts of aircraft surfaces that are easily prone to ice accumulation,and the materials used vary.Aiming at the potential icing problem at the lip of the leading edge of aircraft engines,this thesis uses laser-induced surface meshing of titanium alloy to produce a surface with anti-icing and anti-frost effect.The surface morphology was observed by optical microscope,scanning electron microscope and white light interferometer.And by adjusting the laser parameters,the modulation law of the microstructure morphology of the titanium alloy treated by the laser was obtained,and the formation mechanism of the surface microstructure was emphatically discussed.Secondly,the static contact characteristics and dynamic contact characteristics of the surface in contact with water droplets were measured using a contact angle meter.Using a high-speed camera,the contact process of water droplets hitting the surface at low Weber numbers was observed.According to the microstructure morphology and chemical element distribution characteristics of the surface,the influence mechanism of different laser parameters on the surface hydrophobicity is discussed in this thesis.The results show that: the pulse width has a limited effect on the surface ablation effect.The oxygen element did not show significant changes during the pulse width increase.It mainly influences the final surface morphology by changing the laser depth of action and action time;the scanning speed not only changes the layer structure of the surface,but also significantly reduces the input of oxygen elements during the laser processing,which affects the surface hydrophobicity at both structural and chemical aspects.Finally,according to the different accumulation forms of surface ice layers,this thesis sets up a cold surface frosting experiment and a large water droplet freezing experiment to study the frost and anti-icing properties of the surface respectively.The surface morphology and surface wettability were analyzed to analyze the ice and frost suppression principle of the hydrophobic surface.The results show that: The frost suppression performance of the surface is mainly related to the surface structure morphology and surface hydrophobicity.Hydrophobicity and surface structure can affect the frosting amount by producing different surface frost crystal distributions;The ice resistance of a surface is related to the hydrophobicity of the surface.Dynamic contact properties can greatly influence the cooling freezing process of surface water droplets.Due to the large rolling and contact angle hysteresis,the water droplets in the case of a pulse width of 45 ns appear to collapse and expand during the freezing process.The anti-icing effect of its surface is weakened.The surface hydrophobicity is good for the scanning speed of 250 mm/s,which greatly delays the freezing process of water droplets and presents good anti-icing performance.