Study On Adsorption Characteristics Of Laser Textured SiC Seal Surfaces

Moisture condensation and absorption on gas-lubricated seal surfaces occurs when gas film temperature decreases,which may lead to unstable running of seal film even seal failure.This phenomenon restricts application fields of gas seal technology.Wettability characteristics of laser textured SiC surfaces have been studied in this paper with the aim to control the condensation adsorption of moisture on seal surfaces.Firstly,mathematical model of wetting property with micro-convexes and micro-grooves textures on SiC surface was developed based on the Wenzel model and Cassie-Baxter model.According to the analysis of the presented model,textured SiC surfaces were fabricated with laser processing method.It was show that laser power affects the chemical composition of the SiC sample surfaces.The chemical composition was almost constant when the laser power was lower than 2.4W.However,the content of Si decreased obvious on the surface when the power increased to 2.6W.Then,influence of chemical composition and topography on the SiC surface wettability was obtained experimentally.It was illustrated that chemical composition makes a great influence on the wettability of smooth SiC surface,hydrophilic property raised with the increase of Si content.Meanwhile,the topography affects the wettability obviously of micro-convexed surfaces,the hydrophobicity is improved.And the more obvious hydrophobicity on the smooth substrate,the greater hydrophobicity it was on the textured surface.Anisotropy-grooved surface presented significant anisotropy of wetting.Further,water droplet movement driven by airflow on laser textured surfaces was observed experimentally.It was found that the surface textures affected the dynamic adsorption characteristics.And the airflow and slop of sample had an obvious influence on the waterdrop movement on the textured surfaces.It was easier to spread on the textured surfaces.With the increase of tilting angle,the elongation length of water increased firstly and then decreased.Finally,seal experiment with moisture gas was carried out so as to analyze influence of surface topography on adsorption ability of SiC seal face.Experimental results show that water droplet condensed on the high pressure side.Under shear of seal airflow,water condensation gradually occurred on the seal face.Part water film was observed in the gas lubricating zone when the film thickness became smaller.The surface micro-groove textures made the water drops move along the boundary of spiral grooves.According to the above analysis,laser surface texturing method was introduced to the design of gas face seal so as to control condensation adsorption by changing surface wetting properties,which provides basis for stability design of gas seal face under extreme conditions such as high pressure,low temperature and medium critical phase transition.This work is helpful in solving the condensation failure problems,expanding the gas seal application field,and has an important significance for engineering applications.