Test And Analysis Of Friction And Wear Properties Of Nickel Graphite Coating

The seal coating plays an important role in maintaining the sealing of the engine gas path and improving the efficiency of the engine.The seal coating has become an indispensable material for aero engines.After repeated use of aero-engines,the wearable coatings may fall off in a large area,so it is very important to study the performance changes of the seal coatings under heat treatment conditions.In this paper,flame spraying technology is used to prepare nickel graphite coating on TC11 alloy plate,and the microstructure,porosity,hardness and hardness of nickel graphite coating after heat treatment at room temperature and 200-400 ℃ for 400-2000 h are studied.Combined with the strength change law,the friction and wear mechanism of the nickel graphite coating was studied using a high temperature vacuum friction and wear testing machine to obtain the effect of temperature on the wearability of the coating.The main research contents are as follows:(1)X-ray diffractometer,scanning electron microscope,Image J software were used to test and characterize the phase,microstructure,porosity and hardness of nickel graphite coating samples before and after heat treatment.The test results show that the graphite phase,nickel phase and Ni O phase mainly exist in the nickel graphite coating,and the porosity is about 15%.As the heat treatment temperature increases,the time becomes longer,the degree of nickel oxidation increases,the porosity increases,and the characteristic peak of graphite weakens and disappears.(2)Use a Vickers hardness tester to test the hardness of the surface,cross-section,and bonding layer of the nickel graphite coating before and after heat treatment.Combine the digital image technology with a tensile testing machine to test the bonding strength of the nickel graphite coating.The results show that at 200 ℃ or 300 ℃,as the heat treatment time increases,the hardness increases first and then decreases.When the heat treatment temperature is 400 ℃,the hardness of the surface and cross section of the coating is slightly reduced,and the overall hardness value does not change much.The bonding strength of the original nickel graphite coating is only 2.93 MPa.As the heat treatment temperature increases,the heat treatment time increases,and the bonding strength gradually decreases.(3)Use a high-temperature vacuum friction and wear testing machine to test the friction and wear properties of nickel graphite coating at room temperature to 400 ℃.The test results show that the depth of wear increases with the temperature of the friction test.At 25 ℃ to 400 ℃,the wear scar depth increased from 86.86 μm to the maximum value of 155.77 μm.The amount of wear decreases with the temperature of the friction test.At room temperature,the amount of wear is 0.076 g;when the test temperature is 100 ℃,the amount of wear increases to 0.088 g;when the temperature increases to 400 ℃,the amount of wear has fallen to 0.045 g,the coefficient of friction decreases first and then rises with increasing temperature,the coefficient of friction at room temperature is 0.28,300 ℃ reaches the minimum value of 0.13,and 400 ℃ rapidly increases to 0.44;the main wear mechanism of the original sample coating at room temperature is fatigue wear;At 100 ℃ and 200 ℃ test temperature,the main wear of the coating is abrasive wear and oxidative wear;at 300 ℃,the coating wear mechanism is mainly adhesive wear;at 400 ℃ test temperature,the coating wear mechanism is mainly fatigue Wear and adhesive wear.