Study On The Simulation And Preparation Of Diamond Films On The Inner-Hole Of Drawing Dies With Dtnfh

Drawing die is a key part of metal drawing and processing.The wear resistance of the inner-hole surface directly determines the wear and life of the die,and further affect the product surface quality and production efficiency.The diamond coating can be deposited on the inner-hole surface of the die by Hot Filament Chemical Vapor Deposition(HFCVD)technology,which can significantly reduce the wear rate and friction coefficient of the inner-hole surface,greatly improve the die life and production efficiency,and improve the product processing quality.In the current industrial production,the deposition technology with hot filament through the hole(DTFH)is widely used.However,its scope of application is narrow.It’s not applicable for drawing die with small aperture(diameter Φ≤3mm),and not efficient to be applied on the drawing die with large aperture(diameter Φ20≥mm).The small wire-drawing die and the large tube-drawing die play an important role in the metal drawing industry,and it is urgent to explore the new method to realize the preparation of the diamond coating.In addition,the development of mass production makes the equipment capacity increase,which not only has a serious impact on the uniformity of the surface temperature field,but also seriously restricts the diamond coating growth rate and film quality.In this paper,a novel deposition technology with no filaments passing through the hole(DTNFH)with double-layer hot-filament layout is proposed and studied to achieve the HFCVD diamond films growth on the inner-holes of drawing die.The key factors such as the analysis of the critical factors,the distribution of temperature and flow field,the preparation and characterization of the diamond film are studied.The main contents of the study are as follows:1.Analysis of key influencing factors and feasibility verification ofDTNFH.Due to the more complicated physical field and deposition environment of DTNFH,the key influencing factors are investigated from the point of view of deposition mechanism,gas environment and hot filament radiation.The results show that the effect of the hot filament radiation on the substrate is the fundamental reason that affects the active group and the temperature field of the substrate surface under different depositional geometric environment.The difference between the radiation values of the hot filament on the surface of the inner-hole in DTNFH is investigated.For different hot filament diameter,inner-hole diameter,the plane distance H,the radiation intensity at different angles of the inner-hole is only about 1%,which can meet the requirements of the hole roundness.According to the experiment results,the diamond films can be deposited on the whole zone of the innerhole,if the hole depth is limited with 4D,and thus the structure of the drawing die is redesigned rationally.2.Establishment and verification of simulation model for DTNFH.In this paper,a 3D simulation model is established firstly,which fits the real situation very well.The temperature field is simulated by Fluent software,and the observation points are selected to compare the simulation value and the real value of the temperature.The results show that the error between the simulated temperature and the actual temperature is within 3%,and the change trend is very consistent.The temperature field simulation has practical significance and accuracy.3.Temperature field simulation and experimental analysis of HFCVD diamond films preparation on the small inner-hole of wire-drawing die.The orthogonal design method and the control variable method are respectively used to simulate and optimizate the hot filament parameters and other deposition parameters such as the heat dissipation condition and the supporting cooling method,for the single and batch coating preparation process.The experiment and characterization are carried out with optimized parameters.The simulation parameters are: D1=0.4mm,D2=0.4mm,L1=7.5mm,L2=8mm,S1=7mm,S2=5mm.The results show that the high-quality diamond films withlow stress and good uniformity are deposited on the small inner-holes of wiredrawing dies using the optimized parameters.4.Temperature field simulation and experimental analysis of HFCVD diamond films preparation on the large inner-hole of tube-drawing die.The hot wire arrangement is optimized as follows: three hot filaments are used on the above and below layers.The orthogonal method is used to optimize the filament parameters of the single die: D1=0.4mm,D2=0.4mm,L1=7.5mm,L2=8mm,S1=7mm,S2=5mm.The control variable method is used to optimize the deposition parameters of batching dies.The results of depositional experiments show that the continuous and dense diamond films are deposited on the single and batch tube-drawing dies,which can further verify the accuracy of the simulation.