Study On Synergistic Lubrication Character Of Wear-Resistant Coating And Surface Texture Of Fingertip Seal

As a new type of seal with excellent sealing performance and low processing cost,contact fingertip seal is widely used in aviation industry.However,because the contact fingertip seal works at high temperature and high speed,the fingertip seal is prone to wear,which decreases the fingertip seal performance with time,and the fingertip seal life is short.Spraying coating on the surface of the friction pair or processing the surface texture can effectively improve the friction performance between the friction pair and reduce the wear between the friction pair.In this paper,the coating and surface texture were cooperatively applied to the fingertip seal friction matching pair,and the normal and high temperature friction and wear characteristics of the coating and surface texture cooperatively lubricated fingertip seal friction matching pair were explored by means of the pin plate friction mechanism test,finite element simulation and fingertip seal bench test.The friction and wear mechanism of coating and surface texture co-lubrication was investigated by EDS analysis.The main research contents are as follows:1)In view of the high temperature and high speed conditions of fingertip seal,NiCoCrAlYCr₂O₃-AgMo composite coating was selected for collaborative lubrication of coating and surface texture,and the collaborative lubrication method of coating and surface texture was selected according to the characteristics of coating.AgMo composite powders were prepared by electroless silver plating.The powders had good fluidity and were completely coated.Plasma spraying is used to spray the coating.After spraying,the coating is dense,the interface between the functional layer and the bonding layer is clear,and the surface of the coating is smooth and flat after grinding.The surface texture is processed by laser on the surface of the coating.The texture shape is circular,the diameter is 200um and the surface density is 10%.Reasonable surface texture processing parameters were selected by orthogonal test.The experimental results show that the laser processing power has the greatest effect on the texture processing,the processing times have the second effect on the texture processing,and the processing speed has the least effect on the laser processing.The texture morphology after machining was observed by laser confocal microscope,and the processing parameters were determined as laser processing power of 3W,processing times of 2,processing speed of 400mm/s.2)The fingertip seal friction pair was transformed into pin-disk friction pair by the method of similar PV value to explore the mechanism of collaborative lubrication friction between coating and surface texture.The average contact pressure of fingertip seal under different upstream and downstream pressure differences was obtained by finite element simulation.Compared with optical disc,only texture,only coating,and surface texture co-lubricate the friction and wear characteristics of pin disc friction pairs.The test results show that the average friction coefficient of coating and surface texture is the lowest 0.154,only coating friction coefficient is 0.217,only texture friction coefficient is 0.534,and disc friction coefficient is 0.651.The minimum wear rate of coating-surface texture co-lubrication test pin is 0.11 × 10^-7mm³/（N·m）.The wear rate of coating-only test pin is higher than that of coating-surface texture co-lubrication test pin,and the wear rate of coating-only test pin is much higher than that of coating-only test pin.At normal temperature,the wear rate of the test disk under co-lubrication of coating and surface texture is close to that of the test disk with only coating,but much smaller than that of the test disk with only texture and optical disc.Experiments were carried out at room temperature and high temperature for the co-lubricating friction pairs of coating and surface texture.The test results show that the friction coefficient of coating and surface texture co-lubricating is the lowest at room temperature,the highest at 400℃,the friction coefficient begins to decrease at 600℃,and continues to decrease to 0.26 at 800℃.The wear rate of the test pin firstly increases and then decreases with the increase of temperature,and reaches the minimum 0.055 ×10^-7mm³/（N·m）at 800℃.There is little difference between the wear amount of the test disc at room temperature and high temperature,and the wear depth is less than 10um.The results show that the friction coefficients of the friction pairs of the coating and surface texture are close to each other under different positive pressures.The positive pressure has little effect on the friction coefficient.The wear length of the test pin increases with the increase of the positive pressure,and the wear amount of the test disc increases with the increase of the positive pressure.But the test pin test disc overall wear is small.3)Through SEM scanning electron microscopy and XRD analysis,it is found that the colubrication mechanism of the coating and surface texture is that the existence of the coating protects the entire surface texture from being worn off during wear,and the surface texture plays a role in collecting debris and reducing small wear particles during the whole wear process.The existence of surface texture can reduce the wear of the coating and ensure the continuous function of the coating.At high temperature,the coating will be oxidized to form Ni-based oxides and molybdic acids to reduce wear,ensuring that the coating and surface texture lubrication has better friction and wear characteristics at room temperature and high temperature.4)The finite element simulation was used to compare the wear amount and contact pressure changes of only coating and coating-surface texture co-lubrication.The simulation results showed that the contact pressure of coating-surface texture co-lubrication and coating-surface texture co-lubrication and coating-only pin-disk friction pairs changed in the same trend over time during the wear process,and the maximum contact pressure shifted slowly from just below the spinning side to the rotating center.However,it is difficult for the contact pressure of the coating and surface texture to keep stable.,and the contact pressure will change with wear.Only the contact pressure of the coating friction pair will keep stable.with wear.The wear amount of coating and surface texture co-lubricating test pin increases directly with the increase of time,and the error of wear amount in simulation and test is small.5)By comparing the leakage amount of fingertip seal with the coating alone and the collaborative lubrication of coating and surface texture,the simulation results show that the existence of surface texture can effectively play a spoiler effect and reduce the flow rate of fluid flowing through the leakage gap of fingertip seal.The fingertip seal leakage of colubricated fingertip with surface texture is reduced by 32.5%compared with that of coated fingertip seal only.