Study On Preparation And Friction And Wear Characteristics Of Surface Coating For Special-Shaped Textured Cutting Tools

When metal is machined,the severe wear of workpiece material on tool surface is an important reason for tool failure and reducing its service life.It has been a research hotspot to improve the friction and lubrication performance between the surface of the tool and the workpiece by performing certain surface modification treatment on the tool.Surface texture technology and surface coating technology are the two most popular surface modification technologies.The surface texture not only reduces the direct contact area between the friction pair surfaces,but also stores the lubricating fluid to achieve dynamic pressure lubrication and secondary lubrication effects.The anti-friction,anti-wear and lubrication functions of the solid self-lubricating material also improve the tribological properties of the material surface.The advantages of the two methods are applied to the tool surface to improve its tribological characteristics.The YT15 cemented carbide is used as the base material.Fabrication of triangular,triangular groove and semi-circular annular micro-textures with different occupancies by laser processing technology.The fluid simulation analysis of each micro-texture unit under the same characteristic parameters shows that the liquid lubrication film flowing through the above three micro-texture pits has high hydrodynamic pressure due to the effect of liquid reflux and convection in the pits,especially when the micro-texture shape is semi-circle annular.By adjusting the speed and load values,the triangular,triangular groove and semi-circular annular textured specimens with different area occupancies were tested.The results show that when the area occupancy of micro-texture on the working surface is about10%,the three groups of specimens with different morphologies have the lowest total friction coefficient and the most stable.Particularly,the specimen with semi-circle annular texture shows the best tribological properties.WS₂/Zr composite coatings were prepared by magnetron sputtering on the surface of specimens with special texture,which occupied about 10%of the total area.Combined with ANSYS simulation,the related properties of the composite coatings were tested and analyzed.It is found that the addition of the Zr transition layer effectively improves the stress concentration between the WS₂ coating and the YT15 cemented carbide substrate,and reduces the residual stress gradient between the coating and the substrate.The obtained composite coating has clear shape and uniform distribution,and the crystal structure has a preferential growth orientation,high film-based bonding force and high microhardness,and the thickness of the composite coating is uniform,and is maintained between 5?m and 5.5?m,in line with the requirements of subsequent tests.Comparative frictional wear under the same conditions for non-textured uncoated polished specimens,simple textured specimens with different microtexture profiles,and textured coatings with microtexture and coating synergistic effects test.The friction characteristics and wear mechanism of the three working surfaces were analyzed.Textured specimens of different shapes exhibit a lower and more stable coefficient of friction than purely polished parts.The reason is that the micro-texture reduces the direct contact area between the surfaces of the friction pair and the micro-texture exerts dynamic pressure lubrication and secondary lubrication.The coating material on the textured surface can act as a solid lubricant in the position where the micro-convex body on the two surfaces contacts directly when the lubricant does not work.The storage and collection of coating materials by micro-texture pits also enhance the secondary lubrication effect.Therefore,the textured coating specimens exhibit the most excellent tribological properties,especially the semi-circle annular textured coating specimens have the lowest and most stable friction coefficient of the working surface.On the basis of common cemented carbide cutters,semi-circle annular textured cutters and semi-circle annular textured coated cutters were prepared.The cutting and wear properties of three groups of cutters were studied by cutting 45 Quenched and tempered steel.The results show that for the tool with semi-circle annular micro-texture and WS₂/Zr composite coating acting on the tool surface at the same time,its own three-dimensional cutting force is much lower than that of the tool with semi-circle annular micro-texture acting alone and the common tool.Meanwhile,the average friction coefficient of the rake face is also reduced.There is a large amount of iron chip bonding on the rake face of common cutting tools.The rake face of semi-circle annular textured tool has only a small amount of iron chips bonding.There is no iron chips bonding on the rake face of semi-circle annular textured coated tool,and the wear area of semi-circle annular textured coated tool is mostly peeling of coated film.Coating is prepared on the basis of micro-texture,which enhances the wear resistance and bond resistance of the tool itself.