| Chemical Vapor Deposition(CVD)diamond film has good mechanical and chemical properties.It is often coated on the end face of the mechanical seal ring to improve its sealing performance.In-depth understanding of the tribological properties of diamond films under different working conditions can provide an important theoretical basis for the successful application of diamond coatings on the end faces of mechanical seal rings.In this paper,based on tribological experiments,we combined with electron microscope(SEM),Raman spectrometer,energy spectrometer and step instrument,etc.to learn the friction and wear properties of diamond film in different working conditions(test parameters,abrasive medium,acid-base medium and surface Texture state).The results are as follows:1.The friction test parameters have a significant effect on the tribological properties of the diamond film.When the normal load increased from 8 N to 20 N,the friction pair reached a lower steady state value of the friction coefficient more quickly.Because the increased load could aggravate the local graphitization of the diamond film,thereby optimizing the friction interface lubrication performance.In addition,when the friction speed reached 200-400 rpm,the friction coefficient of the friction pair and the wear rate of the grinding balls reached the lowest values.Respectively,they were 0.0758 and 4.48 × 10-4 mm3N-1m-1.This is due to the fact that when the speed of alternating speed increases,the change of friction speed will lead to the loss of friction heat,which may alleviate the graphitization process to weaken the friction lubricity,and thus reduce the friction performance of friction.2.The acidity,alkalinity,salt content,abrasive particle content and abrasive particle size of the friction fluid will affect the friction and wear properties of the diamond film.After adding 10 g of W5 diamond abrasive grains,the MCD/Si3N4 friction pair showed the best tribological performance.That is to say,the corresponding friction coefficient was 0.076 and the wear rate of the grinding ball was 5.93×10-4 mm3N-1m-1.Because the addition of an appropriate amounts of abrasive particles in the friction fluid will enhance the bearing capacity of the lubricating film;when the abrasive amount was excessive,it would cause a large amount of abrasive particles to aggregate,forming large diamond agglomerates similar to W10 abrasive particles.Thereby it could destroy the stability of the lubrication system properties and reduce the tribological properties of diamond films.Compared with water lubrication,the friction coefficient and ball wear rate of NCD/Si3N4 friction pair under acid-base solution would be significantly reduced.The reason is that hydrogen ions and hydroxide groups will affect the hydrolysis of the silicon nitride surface,thereby affecting the friction coefficient and the wear of the silicon nitride balls.In the salt solution,the stability of the lubricating film was increased by increasing the concentration of the friction fluid according to the fluid lubrication effect,and then the friction and wear were slowed down.3.The reasonable laser micro-texture spacing has a certain improvement effect on the tribological properties of the diamond film.When the texture spacing was 90 ?m,the friction coefficient of the diamond film and the wear rate to the grinding balls both reached the lowest values,which were 0.097 and 2.78×10-4 mm3N-1m-1,respectively.This can be explained that the micro-texture on the surface of the film will increase the wettability of the friction interface to water,so it can form a stable dynamic pressure liquid film.When the texture spacing is too large or too small,it will affect the water absorption of the diamond film surface,thus by changing the lubricity of the lubricating film,the tribological properties of the diamond film are not optimal. |
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