Research On Stress Control Technology Of Combustion-resistant Coating By Electric Spark Deposition In Kerosene

Titanium alloy has excellent comprehensive performance,so it has become an irreplaceable important material for high-performance aircraft engines to reduce weight and improve thrust-to-weight ratio.However,titanium alloys have higher combustion sensitivity.The working environment of an aero engine is in a state of high temperature and high pressure,which is easy to catch fire and pose a serious threat to the safe use of the aero engine.How to prevent the above accidents has become a field in which various technologies compete for practical application.In this paper,without changing the existing structure of the engine and the materials used for parts,the electric spark deposition in kerosene was studied.The compressive stress combustion-resistant coating was prepared on the surface of titanium alloy parts to verify the combustion-resistant coating of the flame retardant coating.The main conclusions of this paper are as follows:1.This paper studies the ESD process in kerosene and compares it with the ESD process in argon.Then,the surface roughness,thickness,hardness and other properties of the flame retardant coating prepared in two different media were tested.The test results showed that the coating prepared in kerosene performed better.2.In order to realize the automation of the coating preparation process and reduce the influence of kerosene impurities on the coating quality,this paper designs and builds a set of automated system for electric spark deposition in kerosene.The system design mainly includes two parts:kerosene filter and electric spark deposition automation device.Select and design its components and build the system,and then verify the coating preparation.The verification results show that the structure of the coating is dense without obvious defects.3.In this paper,the residual stress of the combustion-resistant coating was detected by the Prism residual stress test system.The test results show that:the whole coating prepared in argon shows tensile stress,the maximum tensile stress reaches 1045MPa;the whole coating prepared in kerosene shows compressive stress,the maximum compressive stress reaches-91.2MPa.The tensile-compressive transition of the residual stress in the coating was achieved by the ESD process in kerosene.Then,the high-cycle fatigue performance of the sample was tested.The fatigue life of the sample prepared in kerosene can reach 3×105 times,which is a big improvement over the sample prepared in argon.4.The existing droplet method resistant combustion test system has the problems that the gas heating temperature can not reach 400? and the heating speed is slow.The heating tube in the heating system was modified and a temperature test was carried out.The test results showed that the temperature of the gas at the outlet of the heating tube can reach up to 460?,and the gas heating time was shortened to 0.5h.Finally,the flame retardant performance of the flame retardant coating is verified on the system.The test results show that the coating prepared in kerosene exhibits excellent flame retardancy when the temperature of the sample is lower than 700?.In summary,on the surface of the titanium alloy,the combustion-resistant coating is prepared by the electric spark deposition process in kerosene,which realizes the transformation of the coating stress from tensile stress to compressive stress,and shows good combustion-resistant performance.It provides a new way to solve the fire and combustion problem of aero-engine titanium alloy parts,which is of great significance for the engineering application of this technology.