不锈钢表面Cr-Pd合金电沉积及镀层在强还原性介质中的耐蚀性

通过选择络合剂、缓冲剂及采用方波脉冲电流和优化电镀工艺, 在酸性镀液中实现了Cr-Pd共镀, 并在不锈钢表面制备出均匀致密且与基体结合良好的Cr-Pd合金镀层. 通过改变镀液中铬盐和钯盐的相对含量, 可以大范围改变镀层成分. Cr-Pd合金镀层可显著提高不锈钢在高温还原性腐蚀介质中的耐蚀性, 在沸腾的20%(质量分数)H₂SO₄溶液中, Cr-Pd合金镀层使316L不锈钢的腐蚀速率降低了4个数量级以上. 镀层中的Cr和Pd对致钝具有协同促进作用, 当镀层中含有2.5%Pd(质量分数)时即具有明显的促进钝化效果, 含33.3%Pd镀层对不锈钢的保护效果与纯Pd镀层相当.     

固溶处理对铸造AM50镁合金腐蚀力学性能的影响

研究了铸造AM50镁合金固溶处理后的组织及腐蚀力学性能的变化规律。结果表明,固溶处理后,由于大量Al固溶进α-Mg中,AM50镁合金相组成主要为α-Mg固溶体。此外,固溶处理没有改变AM50镁合金的断裂机制,仍为准解理断裂。受最大蚀坑深度和固溶强化理论影响,在腐蚀时间为24 h前,镁合金固溶处理后的腐蚀剩余强度高于铸态;而在72 h至336 h之间,固溶处理后的镁合金剩余强度低于铸态;在432 h时,固溶处理后的合金剩余强度重新高于铸态合金。铸态和固溶处理后AM50镁合金的腐蚀速率均呈现出先大后小的规律,这种现象主要由镁合金在NaCl溶液中的腐蚀原理决定的。     

不锈钢和镍基合金在高温高压醋酸溶液中的腐蚀行为

采用特制高压釜设备,研究304L不锈钢、316L不锈钢、317L不锈钢和镍基合金(Incoloy 800)在高温高压醋酸溶液中的腐蚀,初步探讨了不锈钢和镍基合金在醋酸溶液中的腐蚀机理及Ni和Mo元素对提高不锈钢耐蚀性能的影响.结果表明,温度对不锈钢和镍基合金耐蚀性有显著影响,随着温度的升高,腐蚀速率逐渐增大,当温度升高到一定值,不锈钢的耐蚀性会急剧下降.在低温醋酸溶液中,Ni对于提高不锈钢耐蚀性是有益的;在高温醋酸溶液中,Ni对于提高不锈钢耐蚀性没有显著影响.在低温醋酸溶液中,Mo对于提高不锈钢耐蚀性没有显著影响;在高温醋酸溶液中,Mo对于提高不锈钢耐蚀性是有益的.     

Corrosion behaviour of an Fe3Al-type intermetallic in a chloride containing solution

The corrosion behaviour of an Fe₃Al-base intermetallic compound with different crystal structures in a chloride containing solution has been investigated. The corrosion current densities of this intermetallic were independent of the material crystal structure showing a passive state stable with time. These corrosion rates were of the same order of magnitude as for 316L stainless steel. The pitting corrosion resistance evaluated by means of cyclic anodic polarization curves was high for all different states. Amongst the different crystal structures of this intermetallic alloy, the two ordered states present the lowest pitting probability. This Fe₃Al intermetallic shows higher pitting corrosion resistance than the 316L stainless steel but its capacity for repassivation is lower. A damaging factor of influence on the pitting corrosion behaviour is the presence of non-metallic inclusions on the surface which reduce the pitting corrosion resistance by almost a half.     

Corrosion behaviour of single and double layer hydroxyapatite coatings on 316L stainless steel by plasma spray

AISI316L stainless steel is extensively used in orthopedic and dental applications. However, this alloy exhibits low integration behaviour when it comes in contact with surrounding bone tissue and implant healing duration can be as much as few months. The aim of this study is the fabrication of biocompatible hydroxyapatite (HA) coatings on stainless steel substrate in order to accelerate the process of osseointegration of implants. The biocompatible single layer of Titania (TiO₂), Hydroxyapatite and bi-layer TiO₂/HA coatings were deposited by atmospheric plasma spray on 316L stainless steel. Coated and uncoated stainless steel specimens were incubated in simulated body fluids and 0.9% NaCl solutions for 1h and 7 days. In vitro electrochemical-corrosion evaluation of coated and uncoated stainless steel specimens have been investigated by Tafel extrapolation and linear polarization methods. Results indicates that corrosion resistance of single layer HA coated stainless steel specimens are superior to single layer TiO₂ and bi-layer HA/TiO₂ coated stainless steel specimens.     

Effect of Solution Treatment on Microstructure and Corrosion Properties of Mg–4Gd–1Y–1Zn–0.5Ca–1Zr Alloy

The as-cast multi-element Mg–4Gd–1Y–1Zn–0.5Ca–1Zr alloy with low rare earth additions was prepared, and the solution treatment was applied at different temperatures. The microstructural evolution of the alloy was characterized by optical microscopy and scanning electron microscopy, and corrosion properties of the alloy in 3.5% NaCl solution were evaluated by immersion and electrochemical tests. The results indicate that the as-cast alloy is composed of the a-Mg matrix,lamellar long-period stacking-ordered(LPSO) structure and eutectic phase. The LPSO structure exists with more volume fraction in the alloy solution-treated at 440 °C, but disappears with the increase in the solution temperature. For all the solution-treated alloys, the precipitated phases are detected. The corrosion rates of the alloys decrease first and then increase slightly with the increase in the solution temperature, and the corrosion resistance of the solution-treated alloys is more than four times as good as that of the as-cast alloy. In addition, the alloy solution-treated at 480 °C for 6 h shows the best corrosion property.     

相对流速对316L钢焊缝在液态铅铋合金中腐蚀行为的影响

在核工业领域,316L不锈钢因其优异的性能常被作为核用钢种,液态铅铋合金常作为加速器次临界驱动系统(ADS)的冷却剂,高速流动的液态铅铋合金(LBE)会对316L不锈钢焊缝造成氧化腐蚀,同时氧化腐蚀后的产物也会对液态LBE造成污染,所以研究316L不锈钢焊缝在液态铅铋合金中的腐蚀行为具有重要意义. 文中对比研究了使用母材作为焊丝进行TIG焊的316L不锈钢焊缝在550 ℃动态(相对流速为1.70,2.31,2.98 m/s)液态LBE中的耐腐蚀性能,试验时间为1 500 h. 结果表明,三组试样都生成了双氧化层,外氧化层主要为Fe₃O₄,内氧化层主要为FeCr₂O₄,内氧化层相对于外氧化层较致密;随着流速的提高,元素的传质过程变快,氧化腐蚀加剧,内氧化层增厚.     

Corrosion behaviour of a dissimilar joint TIG weld between austenitic AISI 316L and ferritic AISI 444 stainless steels

The AISI 444 stainless steel (SS) has become an option to substitute the AISI 316L SS because of its low cost and satisfactory corrosion resistance. However, the use of AISI 444 alloy tubes in heat exchangers causes the welding of a dissimilar joint. The aim of this study was evaluate the corrosion resistance of the tube-to-tubesheet welded by a TIG process composed of AISI 316L and AISI 444. Preparation of samples was executed through replication of tube-to-tubesheet joints. In order to test the corrosion resistance of the welded joint, the following tests were applied: sensitisation, mass loss from room temperature up to 90 °C and electrochemical corrosion tests in 0.5 mol/L HCl and 0.5 mol/L H₂SO₄ electrolytes. The results have shown that the dissimilar joint suffers galvanic corrosion with increased degradation of the heat-affected zone of the AISI 444 tube. Nevertheless, the mechanisms of localised corrosion (pit and intergranular) were more active in the AISI 316L alloy. It is concluded that the dissimilar joint showed better corrosion resistance than the welded joint composed solely of AISI 316L at temperatures up to 70 °C, as the conditions observed in this work.     

AZ91D镁合金电偶腐蚀的扫描Kelvin探针研究

利用扫描Kelvin探针技术(SKP)研究AZ91D镁合金与316L不锈钢偶接件在盐雾试验中电偶腐蚀规律。通过在中性盐雾试验不同周期的表面腐蚀形貌的观察和伏打电位分布图的测量结果分析表明,AZ91D镁合金电偶腐蚀效应与偶接阴阳极的伏打电位差密切相关,AZ91D镁合金与316L不锈钢偶接件存在较大的电位差(约为–1.28V),其电偶腐蚀效应非常显著。在盐雾试验初始阶段,腐蚀主要发生在偶接界面AZ91D镁合金一侧,该腐蚀区域的伏打电位增加幅度较大,而316L不锈钢受到保护没有发生明显腐蚀。随着盐雾试验时间的延长,AZ91D镁合金腐蚀加快,腐蚀产物覆盖区域不断扩大,24h盐雾试验后,偶接件的平均伏打单位差由原始的–1.29V增加到–1.53V,AZ91D镁合金的电偶腐蚀效应加大。由于AZ91D镁合金在盐雾中生成的腐蚀产物对基体具有一定的保护作用,当腐蚀产物不断增加并覆盖表面,偶接件的电位差减小导致AZ91D镁合金的电偶腐蚀效应降低。     

相变伪弹性对NiTi合金多相流损伤的影响

在旋转圆盘仪多相流损伤实验中，NiTi合金表现出十分良好的抗冲刷磨损及冲刷磨损联合作用性能，拉伸和循环应力－应变力学测量表明，NiTi合金具有橡皮弹性吸收能量的相变伪弹性特点，分析认为，相变伪弹性是该合金表现出良好抗损性能的主要原因。     

316L不锈钢在高含氯离子乙二醇中的腐蚀行为

采用失重法实验研究了温度、Cl-浓度对316L不锈钢腐蚀动力学行为的影响;实验判别了316L的晶间腐蚀倾向.结果表明:在C1-质量浓度为36 516 mg/L,Fe3+质量浓度为776 mg/L的情况下,316L的腐蚀速率随温度的升高而增大,温度超出60℃时腐蚀速率迅速增大,120℃时腐蚀速率达到最大值0.0781 m...     

新型热扩散法制备耐海洋环境腐蚀钢筋及其耐蚀性

通过热扩散工艺在自行研制的钢筋原坯表面形成一层化学成分满足不锈钢要求且耐蚀性能优异的"类不锈钢"表面层。采用XRD、SEM及EDS对热扩散层的相结构、表面形貌和截面成分分布进行了分析和表征。通过浸泡加速腐蚀试验、动电位极化曲线和电化学阻抗谱研究了HRB400、316L以及"类不锈钢"钢筋试样在含氯离子混凝土模拟孔隙液中的腐蚀行为及规律。结果表明,热扩散层主要由Cr_(23)C_6、Fe-Cr和Cr_2N等相组成。在含有氯离子的混凝土模拟孔隙液中,"类不锈钢"钢筋的耐蚀性比HRB400提高了287.4倍,比316L提高了1.4倍。"类不锈钢"钢筋的腐蚀电流密度是HRB400的1/299,是316L的1/223。"类不锈钢"钢筋的极化电阻R_p值是HRB400的28.7倍,是316L的4.5倍。因此,"类不锈钢"钢筋在混凝土模拟孔隙液中的耐氯离子腐蚀性能优于316L和HRB400。     

炼油加工过程中氯离子与硫离子对 316L 不锈钢和Monel 合金腐蚀的影响

目的研究常减压装置高温原油馏分及塔顶水相中氯离子、硫离子含量对316L不锈钢和Monel合金(镍基合金)腐蚀的影响。方法通过腐蚀挂片实验,获得316L不锈钢和Monel合金在含不同浓度氯离子和硫离子的水相、油相中的腐蚀速率变化规律。利用扫描电子显微镜,研究316L和Monel合金表面腐蚀后的微观形貌,探讨两种离子对316L不锈钢和Monel合金腐蚀的影响规律。结果在酸值较高的脱后原油中,316L不锈钢和Monel合金的腐蚀速率分别为0.0091,0.0248 mm/a;在酸值较低的常二段馏分中,316L不锈钢和Monel合金的腐蚀速率分别为0.0078,0.0031 mm/a。在常二段馏分中,加入600mg/L氯离子和30 mg/L硫化钠时,316L不锈钢和Monel合金的腐蚀速率分别为0.1755,0.1707 mm/a。在相同条件的脱后原油中,316L不锈钢的腐蚀速率为0.0545 mm/a,Monel合金的腐蚀速率为0.1281mm/a。结论油相中氯离子含量较低时,环烷酸腐蚀占主导因素;而氯离子含量达到较高水平后,氯离子对腐蚀的影响占主导作用。316L不锈钢和Monel合金的腐蚀速率都随氯离子含量的增加而增加,并且硫离子的存在对腐蚀也有一定的促进作用。在塔顶水相中,氯离子和硫离子均对Monel合金腐蚀的影响不大。     

Effect of surface oxide properties on corrosion resistance of 316L stainless steel for biomedical applications

Surface passivation is a promising technique for improving the corrosion resistance both in vitro and in vivo as well as the biocompatibility of 316L stainless steel. In this work, we studied the effect of different passivative processes on the in vitro corrosion resistance of 316L stainless steel wire. Characterization techniques such as anodic polarization test, scanning electron microscopy, auger electron spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy were employed to co-relate the corrosion behavior to various surface characteristics and surface treatments. Results showed that all of these surface treatments did not improve the corrosion resistance of the alloy satisfactorily except amorphous oxidation. This improvement is attributed to the removal of plastically deformed native air-formed oxide layer and the replacement of a newly grown, more uniform and compact one which is composed of nano-scale oxide particles with higher oxygen and chromium concentrations. The properties of surface oxide layer, rather than its thickness, seem to be the predominant factor to explain the improvement of in vitro corrosion resistance.     

冷轧变形对CrCoNi合金组织与性能的影响

针对磁悬浮熔炼的铸态CrCoNi合金,在室温条件下,进行变形量为50%的冷轧变形,研究了铸态及变形后合金的物相成分、显微组织、力学性能及耐腐蚀性能。结果发现,铸态CrCoNi合金在变形前后没有发生物相变化,依旧为FCC单相结构;铸态组织分布不均匀,经过轧制变形后,晶粒被破碎与拉长;随变形道次增加,强度提升,塑性下降。同时发现,相比于铸态,经过轧制变形后的CrCoNi合金耐腐蚀性得到改善,且均优于304不锈钢。     

Corrosion behaviour of thermal sprayed nitinol coatings

NiTi alloy is here investigated as an alternative coating to stainless steel since it is considered to possess good corrosion properties. Three different thermal spray techniques (high velocity oxy-fuel -HVOF-, vacuum plasma spray -VPS- and atmospheric plasma spray quenching -APS+Q-) have been used for building the coatings, and electrochemical tests have been carried out for corrosion evaluation. Open-circuit tests have revealed that the VPS-coating shows fairly good corrosion resistance, both in the as-sprayed and polished forms. The HVOF coatings however, showed a strong dependence on the surface conditions and APS+Q is dominated by electrolyte penetration through coating cracks, thus exhibiting a higher i_corr.     

Corrosion behaviour of Lotus-type porous high nitrogen nickel-free stainless steels

Corrosion behaviour of three austenitic Lotus-type porous high nitrogen Ni-free stainless steels exposed to an acidic chloride solution has been investigated by electrochemical tests and weight loss measurements. Polarization resistance indicates that the corrosion rate of Lotus-type porous high nitrogen Ni-free stainless steels is an order of magnitude lower than that of Lotus-type porous 316L stainless steel in acidic environment. The localised corrosion resistance of the investigated high nitrogen Ni-free stainless steels, measured as pitting potential, E_b, also resulted to be higher than that of type 316L stainless steel. The influences of porous structure, surface finish and nitrogen addition on the corrosion behaviour were discussed.     

选区激光熔化MnSi2增强316L不锈钢复合材料的表面质量及耐蚀性能

为改善316L不锈钢在海洋环境下的耐腐蚀性能,通过MnSi₂增强316L不锈钢基体,采用选区激光熔化(SLM)制备MnSi₂/316L不锈钢复合材料。利用Image-Pro Plus软件、光学显微镜、扫描电镜(SEM)及电化学工作站研究了激光功率对316L不锈钢金属基复合材料致密度及耐腐蚀性能的影响,通过Tafel极化曲线和阻抗谱表征其耐腐蚀性能的强弱,并通过点蚀形貌揭示了其腐蚀机理。结果表明:添加MnSi₂是提高316L不锈钢耐腐蚀性能的有效途径。随着激光功率的增大,耐腐蚀性能呈现先提高后降低的趋势,当激光功率达到190 W时,2%MnSi₂/316L不锈钢复合材料的致密度为99.80%,其腐蚀电位为－0.053 V (vs SCE)。同时,2%MnSi₂可以显著改善316L不锈钢的成形质量,提高其耐腐蚀性能,其腐蚀形式为氯离子诱导氯化物生成的点蚀,且点蚀产生位置主要集中在孔隙边界处。     

络合剂对316L不锈钢化学机械抛光效果的影响

为提高316L不锈钢化学机械抛光（chemical-mechanical polishing,CMP）效率,针对络合剂类型对316L不锈钢加工效果的影响及影响机制进行研究。以材料去除率（material removal rate,MRR）和表面粗糙度（R_a）为指标,探究络合剂类型（甘氨酸、草酸和柠檬酸）及浓度对抛光效果的影响。利用电化学工作站、接触角测量仪和X射线光电子能谱仪（XPS）分析络合剂对316L不锈钢CMP加工影响机制。结果表明:当甘氨酸质量分数为0.2%时,能够同时获得较高的材料去除率和较低的R_a,分别为210 nm/min和1.613 nm。高浓度的络合剂对316L不锈钢材料去除率的抑制作用来源于络合剂增强了316L不锈钢表面耐蚀性,降低了表面氧化速度。XPS分析表明部分甘氨酸络合物会吸附于316L不锈钢表面产生缓蚀作用。      

Corrosion behaviour of hot-pressed austenitic stainless steel in H2SO4 solutions at room temperature

The corrosion behavior of hot-pressed stainless steel (HPSS) of Type 316 was investigated. Samples of HPSS with porosity of 10–30% were prepared. The influence of the porosity factor on corrosion behaviour was investigated by potentiodynamic polarization, open circuit potential, identification of corrosion products by EDAX and SEM observation.It was found that porosity of the HPSS is the main factor affecting corrosion resistance. High porosity results in low corrosion resistance. The open circuit potential of the HPSS is about ? 200 mV (VSCE) as compared to 200 mV for the wrought 316 stainless steel. The potentiodynamic measurements indicate that cathodic concentration polarization is achieved at a relatively low current density and secondary active-passive transition is observed at a relatively high current density in HPSS as compared to wrought 316 stainless steel.It is suggested that the main mechanism affecting the low corrosion resistance of HPSS in H₂SO₄ is the evolution of hydrogen concentration cells due to electrolytic stagnation in the interconnected open pores. As a result the surfaces of the interconnected open pores act as an active anode and the engineering sample surface acts as an active cathode.