Study On Synergistic Effect Of Oxidation And Complexation On The Micro-removal Mechanism Of Typical Iron-based Materials

Typical iron-based materials such as pure iron,stainless steel and bearing steel are widely used in daily production and life.Pure iron has essential national defense applications,aerospace and scientific research because of its good permeability,high purity and good cold and hot processing performance.Due to the corrosion resistance of stainless steel,it has been widely used in medical equipment,furniture,industrial equipment and other fields.Bearing steel has been widely used in ultra-precision manufacturing of basic parts such as bearings due to its high hardness,wear-resistance and fatigue resistance.In recent years,the research on the chemical mechanical polishing of iron-based materials is increasing rapidly,but the research on the micro-removal mechanism is not sufficient.Therefore,in this thesis,atomic force microscope(AFM)was used to explore the micro-removal mechanism of iron-based materials under the synergistic effect of oxidation and complexation.Firstly,the effect of in-situ chemical action on material removal was investigated by AFM wear experiments in different environments.Combined with static corrosion experiments,electrochemical experiments,SEM,STEM and EDS,the micro-removal mechanism of oxidation and complexation synergistic effect on pure iron and the micro-removal mechanism of silica abrasive particles on pure iron were further explored.Finally,the surface reaction film of iron-based materials was controlled by in-situ chemical action to realize nanopatterning on the surface of iron-based materials such as bearing steel and stainless steel.The main contents and results of this thesis are as follows:(1)An experimental method for the micro-removal mechanism of iron-based materials was establishedWith pure iron as the research object,the off-line vacuum AFM wear experiments were carried out by the diamond probe.The results showed that the trend of material removal depth and volume was different from the polishing rate in chemical mechanical polishing.On this basis,by exploring the rust law of pure iron in the solution and optimizing the treatment of pure iron samples,the in-situ AFM wear experiments in the solution were carried out.The results showed that the in-situ chemical function at the interface has an important influence on the micro-removal of iron-based materials.The method of in-situ AFM wear experiment in the solution could better reflect the pure iron surface reaction film under in-situ chemical conditions,which laid an experimental foundation for the following mechanism exploration.(2)Revealing the synergistic effect of oxidation and complexation on the micro-removal mechanism of iron-based materialsIn-situ AFM wear experiments of pure iron were carried out by Si O₂ probe.The results showed that the synergistic effect of hydrogen peroxide and glycine affected the micro-removal of pure iron.Low concentrations of hydrogen peroxide promoted the complexation of glycine,and reducing the mechanical strength of pure iron surface and facilitating mechanical removal.The high concentration of hydrogen peroxide made the iron surface passivated rapidly and inhibited the complexation of glycine,and increasing the mechanical strength of the pure iron surface,making it difficult to be mechanically removed.Through the static corrosion experiments and electrochemical corrosion experiments,it was found that the synergistic effect of oxidation and complexation could affect the chemical corrosion of solution on pure iron.Finally,through AFM adhesion and friction tests,combined with SEM,STEM and EDS analysis and characterization,it was further revealed that the iron surface was mainly composed of amorphous oxides,and no subsurface damage was found.Moreover,Si O₂ particles mainly removed pure iron through mechanical function rather than chemical bonding.The studies provided a theoretical basis for the subsequent application of nanostructure processing on the surface of iron-based materials.(3)Surface nano-machining of iron-based materials was carried out based on the synergistic effect of oxidation and complexationFirstly,the nano-processing parameters were optimized.The optimized process parameters were as follows:the plotting load F_n was 10?N,the plotting number N was 5,and the plotting speed v was 2?m/s.Based on this parameter,micropatterns and microstructures were machined on the surface of iron-based materials such as GCr15 bearing steel and 316L stainless steel.Finally,the chemical function was used to regulate the surface reaction layer of iron-based materials,and the application of nano-texture processing was realized on the surface of bearing steel and stainless steel.At last,the micro-removal mechanism of stainless steel was preliminarily explored.It was concluded that the mechanical strength of the stainless-steel surface was changed by in-situ chemical action,and the abrasive particles such as silica and alumina were mainly removed by mechanical function.In summary,in this thesis,AFM is used to study the micro-removal mechanism of the synergistic effect of oxidation and complexation on the chemical mechanical polishing of typical iron-based materials,which further enriches and improves the material removal mechanism in the chemical mechanical polishing of iron-based materials,and will have important guiding significance for the development of the chemical mechanical polishing of iron-based materials in the future.