| In recent years,the state has vigorously developed the aerospace industry and paid more attention to aerospace materials and processing.New materials are increasingly applied to the field of aviation,such as glass-ceramic,carbon fiber composites and particulate reinforced metal matrix composites and the like,are widely used gradually.When these new materials are used for precision small hole processing,higher performance requirements are also imposed on small diameter tools.The small diameter stainless steel tube diamond knife prepared by electroplating has good cutting performance and is prepared conveniently.But there are problems such as coating peeling and poor tool wear resistance during the cutting process.In view of these problems,this paper studies the pretreatment of 0Cr18Ni9 stainless steel substrate,and proposes anodization pretreatment and flash plating process to enhance the combined state of the coating and the substrate.At the same time,based on the performance requirements of the tool carcass material,Ni-CO alloy carcass was selected and preparation process parameters of the carcass metal were optimized to ensure that the tool carcass metal has high hardness and abrasion resistance;Choose the appropriate pre-treatment method of abrasive particles and electroplating process parameters to ensure the diamond content of small-diameter tools and good abrasive particles and carcass combination strength,giving full play to the grinding effect.The main contents of the thesis research include the following aspects:1)Aiming at the problem of easy wear of small diameter electroplated diamond tool carcass binder,the pre-plating process of 0Cr18Ni9 stainless steel was studied,and the corresponding process parameters were determined.The test analysis shows that the sulfamic acid concentration is 150g/L and the electrolyte has a higher degree of anodic polarization at 35℃,which is more suitable for anodic electrolytic activation.At the current density of 300A/dm~2 and an electrolysis time of 60s,the surface of substrate is dense.The oxide film is removed and the crystal grains are exposed.After electroplating nickel,through thermal shock test and cross-cut test,the coating has no peeling and peeling and good bonding strength with the substrate;When the hydrochloric acid concentration is 80ml/L and nickel chloride concentration is 280g/L,the cathode polarization is the largest;On the basis of the above pretreatment,it is verified through multiple cycles of thermal shock tests that the coating has good bonding strength with the substrate.2)Optimizing the material of tool carcass for the problem of easy wear of small diameter electroplated diamond tool carcass binder.Firstly,based on the mechanical properties of nickel-based binary alloys such as microhardness,Ni-Co alloy with a low cobalt content was selected as the tool carcass material.From the microstructure and structure,the effects of cathode current density,cobalt sulfamate concentration,bath temperature,bath p H,and saccharin sodium concentration on the surface morphology,coating composition and microstructure of the Ni-Co alloy coating were investigated.From the perspective of the mechanical properties of the coating,the effects of cathode current density,cobalt sulfamate concentration,bath temperature,and saccharin sodium concentration on the microhardness,wear resistance and wear morphology of Ni-Co alloy coatings were investigated.Based on comprehensive test and analysis results,the optimized process parameters of the electroplated carcass materials are:current density 2A/dm~2,cobalt sulfamate concentration 14g/L,bath temperature 35°C,p H3.5,sodium saccharin concentration 0.5g/L,a tool carcass alloy with high hardness and good wear resistance can be obtained.3)The technology research of electroplated small diameter stainless steel tube diamond tools was carried out,and the effects of different diamond pretreatments on the surface morphology of the tools and the bonding strength with the carcass were explored.The analysis shows that the strongly oxidized diamond particles are tightly bound to the Ni-Co alloy carcass,and the surface of the composite coating is evenly distributed,while the bonding strength of the diamond after only the purification treatment is weak.Surface metallized diamond abrasive grains easily lead to agglomeration,lamination,and poor bonding.4)A revolution-rotation composite motion electroplating processing device was set up.The effects of different electroplating tool process parameters,including the cathodic current density of buried sand,the buried sand time,and the thickening time on the tool morphology,particle content,and grinding performance were studied.The research shows that the cathode current density of buried sand 2A/dm~2 can avoid scorching.Under the sand burying time of 15min and the thickening time of 90min,the higher abrasive content and uniformity of abrasive grain distribution on the tool end face can be ensured,and the abrasive cutting performance,giving full play to the role of abrasive particles to improve life.5)Tool prototypes were prepared,and the drilling process was used to verify the effectiveness of the improved process,which can alleviate the current problems of low bonding strength,poor wear resistance and low service life of electroplated tools. |
