Study On Tribological Properties Of Textured Working Surface On Conical Dies

The contact region between wire and conical die is in a state of high pressure during drawing processing.Severe friction and wear may result in serious damage of the conical die.As surface modification technology,the surface texture provides a new method to improve friction characteristics of conical dies.Compared with coating technology and modified materials technique relying on contact to realize lubrication effect,the surface texture utilizes bearing capacity of lubricating film to avoid effectively the loss of materials result from friction pairs' contact.The surface texture is defined as morphology arrays owning particular geometric dimensions and arrangement on the working surface.The surface texture reduces friction and wear through decreasing the contact area of friction pairs.Additionally,it can utilize the storage of lubricating oil to realize hydrodynamic lubrication and second lubrication to reduce wear.Contact condition will be changing in the process of sliding contact.The quality of processing and whether the texture design is based on the friction mechanism will have a significant impact on evaluation of tribological properties.According to research results,the micro-pits or micro grooves under lubricating environment can realize fluid hydrodynamic lubrication,cavitation effect and inertia effect.Especially,hydrodynamic lubrication is obvious when the surface texture own the convergent outlet in the vertical section.Cavitation effect can generate cavity which inhibits the negative pressure,nevertheless it leads to the appearance of cavitation micro-pits which would become sponge shape.That reduces seriously parts service life.How to improve the pressure of surface texture's convergent outlet and bearing capacity of the region is the key to the study.Based on friction mechanism of the textured working surface,the study founded the model of surface texture under fluid lubricating environment.Calculating contact pressure of friction pairs and using finite element method,the research simulated different shapes of surface texture and designed one type of texture having convergent effect on the working surface.The process technology of texture is widely,such as shot peening,reactive ion etching,high temperature removal technology and micro-cutting.According to different shape parameters,the research used femtosecond laser to engrave cemented carbide specimens working surface.Utilize ultra depth of field instrument to observe surface texture,and the research prepared textured specimens meeting the requirements of design which owned different shapes and area occupancy ratios.Each textured specimens' experiments including four kinds of rotation speeds and loads were taken aiming to research different shape of textured surface's lubrication regularities under different working conditions.Meanwhile,the study drew friction curves of every shape of workpieces according to the area occupancy ratios' influence on friction characteristics.The experimental results showed that lower area occupancy ratios' reduced the effect of hydrodynamic lubrication,however surface roughness was high because of more texture units.Other than common shapes possessing the convergent outlet in the vertical section,the micro-texture model having the convergent effect on the working plane makes full use of grooves' gathering and leading role to get relatively high pressure because of fluid convection.After experiments,the wear mechanism of each specimen was analyzed.Some parameter combinations and working conditions making working surface maintain steady tribological properties were proposed.