Preparation And Application Research Of Alloyed Fe/Ni-Si Intermetallic Compound Infiltration Layer

Fe/Ni-Si intermetallic compounds have excellent comprehensive properties such as high hardness,high-temperature oxidation resistance,corrosion resistance and wear resistance.In order to solve the defect and brittleness question of this kind of material prepared by conventional methods,starting from widening the wide application of intermetallic compound materials,considering that the use of intermetallic compound materials as film materials can play a protective role on the substrate,so the preparation of high hardness intermetallic compound film on the surface of soft steel/nickel material by molten salt non-electrolysis is proposed.On the one hand,alloying can be realized by making full use of alloying elements in the substrate inside to prepare the alloying film.On the other hand,trying to introduce an external alloy source on the surface of the substrate by electroplating methods and obtain an alloyed layer with better performance by adjusting the type and coordination sequence of the electroplating layer.By investigating the corrosion behavior of the alloyed Fe₃Si layer in H₂SO₄,NaCl and NaOH media,the semiconductor properties of the passivation film were fully revealed.By comparing the effect of Fe/Ni-Si alloying layer on corrosion resistance and wear resistance of 2Cr13 steel and nickel materials surface,the main research results are as follows:?1?The infiltration layer prepared on the surface of 2Cr13 and 304 stainless steel was composed of Fe₃Si and Fe ₃Si intermetallic compound layer alloyed with Cr and Ni and the porous diffusion layer underneath.Among them,Cr-and Ni-alloyed Fe₃Si layers on 304 surfaces were the most compact,less defective and thicker.The Fe₃Si infiltration layer shows obvious passivation characteristics in 10%H₂SO₄ aqueous solution,which significantly improved the corrosion resistance of the substrate.In a3.5%NaCl solution,when the temperature was higher than 40?,Fe₃Si exhibited better corrosion resistance than the matrix under the same conditions and plays a role in protecting the matrix.In a 3.5%NaOH solution,the corrosion resistance of Fe₃Si?304?was always lower than that of 304 substrate.?2?A dense passivation film was formed on the surface of Fe₃Si?304?in H₃BO₃/Na₂B₄O_7?10H₂O buffer solution.The passivation film has a double-layer structure.The inner layer was mainly composed of Cr,Fe oxides?CrO₃,FeO?and Ni.The outer layer was composed of Cr,Fe oxides and hydroxides?Cr₂O₃,CrOOH,Fe₂O₃,Fe₃O₄,FeOOH and Fe?OH?₃?.With the increase of alloy elements and film-forming potential,the decrease of Cl^-concentration and film-forming temperature,the passive film resistance and charge transfer resistance increase,the density of impurity states in the film decreases,and the protective effect of the passive film on the substrate increases.The passivation film exhibited n-p-n type semiconductor characteristics,but when Cl^-was added,the passivation film exhibits only N-P type semiconductivity.?3?Surface electroplating Ni/Cu+neutral molten salt infiltration siliconizing composite treatment can be used to prepare Fe₃Si metal compound layer containing alloying elements(Cr,Cu-,?Cr,Cu,Ni?-and?Cr,Ni?-and a corresponding diffusion layer structure on the 2Cr13 steel substrate.The formed alloyed Fe₃Si layer can increase the surface hardness,wear resistance and corrosion resistance against the sulfuric acid solution of the substrate to varying degrees.However,the comprehensive properties of the alloyed Fe₃Si layer obtained by electroplating Ni composite infiltration siliconizing treatment was the best.?4?Molten salt infiltration siliconizing was carried out on the surface of pure Ni substrate and G3 nickel base alloy.The obtained siliconizing layer consisted of a porous diffusion layer inside and a relatively dense silicide layer outside.The surface siliconizing layer had a certain anti-friction and lubrication effect and enhanced the wear resistance of the matrix surface.The corrosion resistance of siliconized specimens in 10%H₂SO₄ solution has been reduced,but there were still obvious secondary passivation characteristics and wider passivation zone.