| In response to the problem of insufficient interfacial adhesion of the hard coating-soft substrate composite system,a new idea of depositing hard coatings on the surface of the ultrasonic rolling textured substrate is proposed by combining ultrasonic rolling surface texturing technology and coating technology.Most of the conventional surface textures are fabricated by subtractive manufacturing methods(e.g.,laser processing,electrical discharge machining,etc.).In this study,ultrasonic surface rolling process(USRP),an isomaterial manufacturing technique,is applied to fabricate substrate surface textures.The smooth substrate surface is converted to the ultrasonic rolling textured substrate surface prior to depositing the coating to reduce the property mismatch between the plastic substrate and the hard coating and to further enhance the interface bonding of the coating-substrate system.Using theoretical analysis,simulation modeling,and experimental verification,the formation mechanism and controllable fabricating parameters of ultrasonic rolling textures on the plastic substrate surface are explored.And the hard coatings are deposited on the surface of the ultrasonic rolling textured substrate.The influence of ultrasonic rolling substrate surface texturing on the mechanical performance,interface bonding properties,and tribological behavior of the hard coating-soft substrate system is systematically investigated.A new idea of fabricating surface textures by the ultrasonic surface rolling process is proposed.Based on the elastic-plastic contact deformation theory,the feasibility and dimensional controllability of surface textures by USRP are analyzed,and the analytical model between the ultrasonic rolling processing parameters and the texture depth is derived.The finite element model(FEM)of the ultrasonic rolling surface texturing process is established,and the formation mechanism of surface textures fabricated by the ultrasonic surface rolling process is revealed.The influence of ultrasonic rolling processing parameters on the dimensional characteristics of surface textures is analyzed.Based on the processing characteristics of USRP,the motion trajectory of the rolling head is designed,and the regular linear arrays are prepared on the surface of the AISI 5140 steel substrate by USRP equipment.The influence of ultrasonic rolling processing parameters on the morphology and dimensional characteristics of substrate surface textures is studied.It is concluded that the step distance,air pressure,and feed speed have significant effects on the texture morphology.The step distance plays a decisive role in the width of the texture,the air pressure has the greatest impact on the depth of the texture,and the feed speed has no significant impact on the geometry of the texture.The surface properties of the ultrasonic rolling textured substrate are systematically investigated.The results show that compared with the PS sample,the ultrasonic rolling textured substrate shifts the diffraction peak to a small angle,implying the induction of residual compressive stress on the substrate surface.In addition,the hardness and hydrophilicity of the ultrasonic rolling textured substrate surface are enhanced.The AlTiN coating is deposited on the surface of the ultrasonic rolling textured substrate by the multi-arc ion plating technology.It is found that the coating showed a well-defined and dense bonding interface with the textured substrate,and the texture profile fabricated on the substrate is retained on the coating surface.The effect of ultrasonic rolling substrate surface texturing on the surface properties of AlTiN coating is systematically studied.Results suggest that the mechanical performance of the coating is closely associated with the surface state of the substrate.The ultrasonic rolling texturing substrate with enhanced mechanical properties can improve the mechanical properties of the coating deposited on its surface,including improving the surface hardness,wettability,and residual compressive stress of the coating.The mechanism of improving the mechanical properties of AlTiN coating by ultrasonic rolling substrate surface texturing is explored.On the one hand,the strengthened mechanical properties of the textured substrate surface enhance the ability to carry the coating.On the other hand,the textures retained on the coating surface change the contact state between the coating and the external load.The cracking behavior and failure mechanism of AlTiN coating deposited on the ultrasonic rolling textured substrate surface are studied by scratch test.It is concluded that ultrasonic rolling substrate surface texturing can improve the critical failure load of the AlTiN coating.In addition,the ultrasonic rolling processing parameters also have a significant effect on the scratching deformation behavior of the coating.Compared with the PSC sample,the interfacial bonding force of the AlTiN coating deposited on the ultrasonic rolling textured substrate surface(APC-0.3)increased by a maximum of 56.6%.The cracking behavior of AlTiN coating deposited on the textured substrate is investigated by indentation test,and it is found that the ultrasonic rolling substrate surface texturing enhances the crack propagation resistance of the coating.The mechanism of enhanced interfacial bonding performance of AlTiN coatings by ultrasonic rolling substrate surface texturing is discussed.The textures provide increased adhesion area and mechanical engagement of the coating on the substrate.The enhanced wettability of the textured substrate surface facilitates the wetting,spreading,and adhesion of coating droplets.The high surface energy and high polar component induced by textured substrate surface promote the bonding between coating and substrate.The residual compressive stress at the interface improves the resistance to crack propagation.The textured substrate with a strengthening layer provides a good bearing surface for coating adhesion.The good synergistic deformation between the textured substrate and the coating enhances the ability of the coating system to resist deformation.The tribological characteristics of AlTiN coating deposited on the ultrasonic rolling textured substrate surface in sliding against GCr15 steel are evaluated by reciprocating sliding friction and wear tests.The following conclusions are obtained:the ultrasonic rolling substrate surface texturing can reduce the average friction coefficient of the coating to a certain extent,and can significantly enhance the wear resistance of the coating.At a sliding speed of 8 mm/s,a load of 15 N,and a sliding time of 1800 s,the wear volume of the steel balls sliding against the APC-0.3 sample is reduced by 49.0%compared to the PSC sample.At a sliding speed of 2 mm/s,a load of 20 N,and a sliding time of 7200 s,the tribological properties of the coating deposited on an ultrasonic rolling textured substrate surface are better than those of the PSC samples under dry friction condition.The improvement mechanism of ultrasonic rolling substrate surface texturing on the tribological performance of AlTiN coating can be revealed from the effects of textures on the surface state and interface bonding.The textures of the coating surface improve the friction contact behavior,and the textures at the interface enhance the adhesion of the coating and the substrate. |
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