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Fabrication And Tribological Behaviours Of Micro-nano Textures On The AlCrN Coatings

Posted on:2017-01-30Degree:MasterType:Thesis
Country:ChinaCandidate:P GaoFull Text:PDF
GTID:2271330485980075Subject:Mechanical Manufacturing and Automation
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The design idea of hard coated micro-nano textured surface which combines effect of micro-nano textures with hard coatings is proposed in this paper. On the basis of analyzing preparation of key technologies, micro-nano groove textures are fabricated on the AlCrN coatings by laser technology, as well as their tribological behaviours are systematically studied. The effect of micro-nano textures on tribological behaviours of AlCrN coatings are illustrated and the friction mechanisms are revealed.Firstly, micro groove textures are fabricated by pulse fiber laser machine, and the effect of processing parameters on the textures morphologies are studied. Combining with the surface properties of AlCrN coatings, the best processing parameters are received:pulse power of 12W and scanning speed of 200mm/s and one-time scanning. Different angles and spacing with the depth of 3μm and the width of 36μm are fabricated by this processing parameters.Nano groove textures are fabricated on the AlCrN coatings by femtosecond laser machine on the basis of analyzing its principle. The influence of processing parameters are studied and the best processing parameters, which are that single pulse power of 3.5μJ and scanning speed of 1000μm/s, scanning spacing of 5μm and one-time scanning, are used to fabricate three kinds of areal density of nano-textures to study the effect of tribological behaviours on the AlCrN coatings. The three kinds of areal density nano-textures are 100%,50% and 25%, respectively.The tribological behaviours of micro textures on AlCrN coatings with different angles, spacing and surface roughness are studied. Results show that micro-textures can improve the tribotogical behaviours of AlCrN coatings. Micro-texture can be more effective improving tribo logical behaviours of AlCrN coatings under low load, high sliding speed and adding lubricant The morphologies of micro groove textures have great effect on the tribo logical performance. The best texture angle is parallel to the sliding direction, and the best spacing is 400μm. Reducing surface roughness of the micro-textures surface can effectively improve wear resistance of AlCrN coatings surface. Friction coefficient of front and back polishing surface do not have much difference, but reducing surface roughness of micro-textures surface can decrease grinding crack size of AlCrN coatings and wear volume of friction ball.Finally, the tribological behaviours of nano-textures on AlCrN coatings with different areal density and different lubricating condition are studied. Results show that nano-textures increase friction coefficient comparing to un-texture surface instead of decreasing it under dry friction conditioa Friction coefficient increases gradually with the increasing of areal density of nano-textures. The main forms of wear are adhesive wear and oxidation wear. Under the condition of adding lubricating grease, nano-textures can effectively reduce friction coefficient of AlCrN coatings. With the increasing of areal density of nano-textures, friction coefficient decreases gradually and time of duration of low friction coefficient increases gradually. Nano-textures can be a storage of lubricating grease and provide lubricating grease continuously. Also, they can be a storage of wear debris. When the nano-textures are filled by wear debris, they lose the ability of provide lubricating grease and four kinds of samples have the same tribological behaviours.
Keywords/Search Tags:micro-nano texture, AlCrN coating, reciprocating sliding friction, tribological behaviours
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