电化学极化及高温氧化的界面反应与合金表面改性新技术

At present, all of the surface odification technologies such as composite coatings, vapor deposition, ion beam-based techniques, sputtering, plasma treatment,.diffusion coating and plating etc are the processes of transporting certain elements or compounds of corrosion resistance from outside on or below the surface of alloys..The aim of the present project is to explore a simple and potential surface modified process by means of the electrochemical anodic polarization and the selective air oxidation at high temperature, which are not required to transport materials to modified surface of alloys. In terms of this idea, two studies have performed: 1.The effects of anodic passivating aging, critical ranspassivation and alternating.voltage(A.V.) modulated passivation on the stability, constitute and corrosion.resistance of passive film formed on Fe-Mn base alloying with Al, Cr, and Si in 50%.HNO3 solution or 1 mol l-1 Na2SO4 solution were studied by way of combined.electrochemical examination and Auger electron spectroscopie(AES)/X-ray.photoelectron spectroscopic(XPS) analysis. After passivation aging in anodic passive.region, the stability, improvement of constitute and resistance to corrosion of passive film increased markedly. For an example of Fe-24Mn-4Al-5Cr alloy,when increased the anodic passivation time, in 50% HNO3 solution from 15 min to 5 h, the active time(Ta) of passive film in 1 mol l-1 Na2SO4 + 0.5 mol l-1 H2SO4 solution prolonged from 300s to 12500s, and the corrosion resistance characterized by polarization curve in 1 mol l-1 Na2SO4 solution is obviously superior to that of Fe-13% Cr-0.1 % C SS. The modified efficiency of passive film for anodic aging in 1 mol l-1 Na2SO4 solution.is inferior to that in strong oxidizing 50% HNO3 solution. The higher the anodic.passivation potential, the longer the aging time and the stronger the oxidizing of electrolyte, the better the property and constitute of passive film aged. The property of modified passive film is mainly dependent on the anodic passivation potential, aging time and oxidizing of electrolyte. Passivating at critical transpassivation potential and.alternating voltage(A.V.) modulated passivation under each of their optimal.passivating parameters were performed in 1 mol l-1 Na2SO4 solution. The results show.that the two passivation methods can increase the active time(Ta) i.e, the stability of passive film of Fe-Mn base alloys containing Al, Cr or Al and Cr and Si in 1 mol l-1 Na2SO4 + 0.5 mol l-1 H2SO4 solution. The results of probing Fe, Mn, Al and Cr ions in the electrolyte solution of passivation by using atomic absorption spectrometer reveal that the preferential dissolution of Fe and Mn will induce the enrichment of Al and Cr in passive film. The electrochemical studies of active time(Ta), anodic polarization curves, and the analysis of pas sivating electrolyte solution using AAS are in agreement and are confirmed each other. 2. The dependence of selective oxidation, Mn-depleted layer and barrie film of oxides on alloying elements and temperture has been studied. For obtaining the efficient barrier layer of mixed oxides in surface of alloy, the oxidation kinetic, surface morphology, phase in dentification of the oxide scale and cross-sectional views of Fe-Mn base alloying with Al or Cr or Al and Cr and Si were studied using cycling oxidation test, scanning electron microscopy(SEM), X-ray diffraction(XRD) and energy probe X-ray icroanalysis(EPMA). The present investigation can be .summarized as follows: a) With in creasing alloying elements from Fe-Mn to Fe-Mn-Al, to Fe-Mn-Al-Cr and to Fe-Mn-Al-Cr-Si, the mass gain – time curves at 700℃ and 800℃ change from almost linear law to sub-parabolic, to parabolic and cubic parabola and to logarithmic law. b) Because of the Gibbs free energy .G0 of.formation for Al2O3 is very low in elements of Fe-Mn-Al-Cr-Si alloy, the preferential oxidation of Al in Fe-Mn base alloys will form a thin layer of Al2O3 and aluminate..This layer

研究铁锰基合金不同条件电化学极化与高温氧化的界面反应、离子迁移、元素贫化与富集及其化合物的分布等规律。人工调控强耐蚀性元素如ＡｌＣｒＳｉ及高价氧化物在表面膜富集而将弱耐蚀性元素如ＭｎＦｅ及其氧化物排除于表层外，提高合金表层耐蚀性。开创合金内源表面改性新技术并提出工艺设计参数。扩大ＦｅＭｎ基合金应用范围和丰富钝化膜形成与高温氧化理论。