磷偏析对低碳钢孔蚀扩展的影响

    选择6种冶金因素各有特点的低碳钢,通过模拟“闭塞腐蚀电池”试验和室内挂片试验,结合金相组织、硫印、磷偏析和腐蚀形貌分析,研究磷偏析对孔蚀扩展的影响.结果表明,腐蚀形貌上呈现出凹凸状的平行腐蚀沟槽,这种平行腐蚀沟槽与磷偏析相关,而不是与沿轧制延伸的夹杂物(硫偏析)或平行的带状组织(碳偏析)相关.凹凸状的平行腐蚀沟槽形成原因是磷在溶液中离解为磷酸根离子,产生微溶的金属盐,在蚀坑的阳极活化区沉淀,从而抑制了阳极溶解.       

碳钢中磷的偏析对坑孔腐蚀的影响

选择五种具有不同冶金特点的碳钢,通过模拟蚀孔的闭塞腐蚀电池试验及室内挂片试验,研究了轧制钢板中磷偏析对坑孔腐蚀扩展的影响。结果表明,磷偏析是形成蚀坑内梯田状腐蚀形态的主要原因;磷偏析及较低的磷含量都加速蚀坑的发展;沿轧向延伸的磷偏析带及夹杂物导致了蚀坑沿平行板面方向的腐蚀扩展速度大于垂直方向的扩展速度。     

碳钢及低合金钢点蚀性能的研究

选择三种典型的碳钢、低合金钢,通过极化试验比较了它们之间的点蚀诱发敏感性和模拟孔蚀的"闭塞腐蚀电池",试验研究了它们之间的孔蚀扩展行为。结果表明,B钢的点蚀诱发能力小于A钢和C钢;在同样的阴极极化电位下,B钢的阳极溶解电流也明显小于后两者。电子探针分析了不同夹杂物在诱发点蚀过程的腐蚀特征,夹杂物是钢中主要的点蚀诱发源。显微分析"闭塞腐蚀电池"腐蚀形貌,发现腐蚀形貌具有平行沟槽状。初步分析原因是沿轧向延伸的磷偏析带及夹杂物所导致的。扫描电镜和能谱仪对腐蚀产物的形貌、成分分析结果表明:B钢的锈层均匀致密,而A钢的锈层呈网状、疏松且有大量裂纹和孔洞。     

碳钢及低合金钢点蚀性能的研究

选择三种典型的碳钢、低合金钢,通过极化试验比较了它们之间的点蚀诱发敏感性和模拟孔蚀的“闭塞腐蚀电池”,试验研究了它们之间的孔蚀扩展行为。结果表明,B钢的点蚀诱发能力小于A钢和C钢;在同样的阴极极化电位下,B钢的阳极溶解电流也明显小于后两者。电子探针分析了不同夹杂物在诱发点蚀过程的腐蚀特征,夹杂物是钢中主要的点蚀诱发源。显微分析“闭塞腐蚀电池”腐蚀形貌,发现腐蚀形貌具有平行沟槽状。初步分析原因是沿轧向延伸的磷偏析带及夹杂物所导致的。扫描电镜和能谱仪对腐蚀产物的形貌、成分分析结果表明：B钢的锈层均匀致密,而A钢的锈层呈网状、疏松且有大量裂纹和孔洞。     

Cr13不锈钢在盐酸溶液喷射冲刷作用下的表面腐蚀形貌表征

研究了Cr13马氏体不锈钢在盐酸喷射条件下腐蚀形貌的局部差异。结果表明,射流与样品表面接触中心区域产生圆状点蚀坑、中心区的四周形成放射性分布的彗星状腐蚀沟槽;随腐蚀时间延长,蚀坑和沟槽密度增加;彗星状腐蚀沟槽由点蚀坑和尾部的沟槽组成;点蚀坑起源于MnS夹杂处,彗星尾部沟槽主要发生在马氏体区,而δ铁素体区没有明显腐蚀。     

低合金钢在海水中局部腐蚀锈层结构的研究

使用光学显微镜、电子探针、电子显微镜、微电化学测试等方法对两种低合金钢在海洋条件下的局部腐蚀锈层结构进行了研究。研究工作表明,低合金钢虽然具有较碳钢严重的局部腐蚀,但当该种合金钢的局部腐蚀锈层具有合金元素富集、致密等特征时,局部腐蚀将受到抑制,其原因是蚀坑内含富集合金元素的腐蚀产物成了难溶性盐,复盖了蚀坑底部基体,阻滞了腐蚀过程,降低了局部腐蚀速度。而在蚀坑外的平坦区域则没有发现合金元素的明显富集——局部腐蚀由向深度方向转而朝着扩大蚀孔直径的方向发展。这种变化的规律可由微电化学的蚀坑内外ΔmV-d曲线明显地看到所研究的钢种中,AlCuP钢具有较为典型的上述特征。NlCuAs钢的局部腐蚀行为与碳钢相近。     

某油田抽油杆断脱失效原因分析

某油田抽油杆腐蚀严重,表面布满腐蚀坑,主要集中在其圆周分布的三分之一的区域,并伴有纵向拉痕;表面另外的三分之二区域没有点蚀坑,只有较浅纵向拉痕的沟槽。对抽油杆表面腐蚀形貌、金相组织和扫描电镜进行分析,揭示其腐蚀失效的原因。抽油杆环境中氧的腐蚀、Cl~-的加速腐蚀作用、盘根及垢粒摩擦腐蚀等因素有关。     

几种典型耐海水钢耐点蚀性能的比较

选择了三种典型的耐海水腐蚀钢,在pH为10的3%(wt.%)NaCl溶液中进行了极化试验,比较了钢的点蚀诱发敏感性;在3%(wt.%)海盐水和人造海水中分别进行了间浸挂片试验和模拟闭塞腐蚀电池试验,评价了钢的点蚀扩展速度;利用金相显微镜、电子探针(EPMA)、扫描电镜(SEM)和X射线衍射(XRD)分析了钢中夹杂物、腐蚀形貌和锈层的特征。结果表明,Ni-Cu-P钢的点蚀诱发敏感性比Cr-Cu-Ni钢强,Cr-Cu-P钢最弱。在相同条件下,Cr-Cu-P和Cr-Cu-Ni钢的点蚀扩展速度接近,但都明显大于Ni-Cu-P钢。四种钢的内锈层主要组成均为Fe3O4、α-FeOOH和和少量的非晶化合物,但Cr-Cu-P和Cr-Cu-Ni钢的内锈层明显比Ni-Cu-P钢致密。在酸化的蚀坑内,Cr可降低钢基体的电位,从而促进蚀坑的扩展;而Ni的添加则提高钢基体的电位,从而有助于降低钢的点蚀扩展速度。     

激光共聚焦扫描显微镜在腐蚀形貌表征中的应用

对N80钢进行了全面腐蚀和沟槽腐蚀试验,采用激光共聚焦扫描显微镜(LSCM)表征其表面的腐蚀形貌,并与宏观观察、扫描电镜和金相显微镜等方法进行了比较。结果表明:利用LSCM分析能够更直观和客观地找到局部腐蚀和腐蚀坑深处,仪器自带标尺还可直接和便捷地测量坑深,由此计算的沟槽腐蚀敏感系数更可靠。     

扩散退火对热浸镀铝锰合金镀层组织结构及性能的影响

采用热浸镀工艺在Q235钢表面形成了Al-2%Mn、Al-13%Mn铝锰系合金镀层,对Al-Mn合金镀层进行了扩散退火处理,并分析了合金镀层的组织结构、表面形貌及抗磨料磨损性能。结果表明:经扩散退火处理后,镀层中的Fe2Al5消失,但出现了新的物相Al8Mn5及Al10Mn3;镀层表面形貌发生了较大变化,块状化合物消失,出现了瘤状物以及氧化腐蚀坑,而Al-13%Mn镀层氧化腐蚀更明显;镀层表面的硬度由830 HV增加到1100 HV左右;扩散退火不利于提高镀层的抗磨粒磨损性能。     

GH4738合金高温扩散退火工艺

借助于Thermal-calc热力学软件计算了合金的平衡凝固相图,以此为依据制定了高温扩散退火处理的试验参数。利用OM和SEM观察了GH4738合金的铸态偏析状况,并用EPMA技术研究了合金铸态以及不同高温扩散退火制度下的元素偏析规律。结果表明,铸态合金中Ti元素偏析最为严重,高温扩散退火处理后Ti元素偏析得到明显改善,经1200 ℃×50 h的高温处理后效果最为显著,同时计算了残余偏析指数随温度的变化曲线,计算结果和试验结果基本吻合。     

Determination of the Fe-Cr-Mo Phase Diagram at Intermediate Temperatures using Dual-Anneal Diffusion Multiples

A recently developed dual-anneal diffusion-multiple approach is employed to the determination of the Fe-Cr-Mo phase diagram at intermediate temperatures. Diffusion multiples of Fe-Cr-Ni-Co-Mo were first annealed at 1200 °C for 500 h to create wide ranges of solid solution compositions. Subsequent annealing of the diffusion multiples at individual intermediate temperatures induced various precipitate phases. Electron probe microanalysis (EPMA) across the interface between large precipitates and the matrix phase provided local equilibrium information for the establishment of equilibrium tie-lines which are utilized to construct the Fe-rich part of the Fe-Cr-Mo isothermal sections at 900 and 800 °C. The Mo-rich part of the isothermal sections at intermediate temperatures was not obtained due to the sluggish kinetics of precipitation and growth, resulting in too small precipitates for reliable EPMA composition evaluation. A complete 1200 °C isothermal section of the Fe-Cr-Mo system is also established from EPMA data on a water quenched diffusion multiple that was annealed at 1200 °C for 500 h only without a second anneal.     

Ti-Ta-Fe合金力学和扩散性能的高通量测定（英文）

结合纳米压痕和扩散偶方法对Ti-Ta-Fe合金富Ti端的力学性能和扩散性能开展高通量研究。通过在1273 K固溶退火25 h制备5组三元Ti-Ta-Fe扩散偶。借助纳米压痕和电子探针等技术确定Ti-Ta-Fe体系体心立方相随成分变化的力学性能。利用实用高效数值回归方法从三元扩散偶的成分梯度中获取1273 K温度下的互扩散系数。基于以上实验结果构建一套Ti-Ta-Fe合金随成分变化的力学和扩散性能数据库。该数据库可用于钛合金热加工过程中的加工变形性能分析。结果表明,控制Fe含量可提高钛合金的硬度和降低杨氏模量。     

退火温度对铜铝复合板界面相演化及性能的影响

采用冷轧复合法制备铜铝复合板,研究退火温度对复合界面金属间化合物的演化及性能的影响。利用电子探针(EPMA)观察复合界面结构,结合EDS、XRD分析界面物相成分,通过剥离测试和室温拉伸试验表征复合板的结合性能。结果表明,随着退火温度的升高,复合界面扩散层增厚,依次生成CuAl₂、Cu₉Al₄和CuAl 3种金属间化合物。CuAl₂和CuAl相的生成破坏了界面结合,导致剥离强度显著下降。在300 ℃及以上温度退火时,复合板发生回复和再结晶软化,其整体拉伸性能优异。综合考虑拉伸性能及剥离强度,冷轧复合法制备铜铝复合板的最佳退火温度为300 ℃。     

Investigation of mechanical and diffusion properties in bcc Ti−Nb−Zr−Sn alloys via a high-throughput method

The mechanical and diffusion properties of bcc Ti−Nb−Zr−Sn alloys in the Ti-rich corner were analyzed through a high-throughput method with the combination of nanoindentation and diffusion couple techniques. Nine groups of quaternary Ti−Nb−Zr−Sn diffusion couples were prepared after annealing at 1273 K for 25 h. The composition-dependent mechanical properties were determined by nanoindentation and electron probe microanalysis (EPMA) techniques. Moreover, the corresponding interdiffusion coefficients were confirmed from the composition gradients of the quaternary diffusion couples using a pragmatic numerical inverse method. A composition-dependent database on the mechanical and diffusion properties was utilized to discuss the processability during the hot working. The results reveal that the solute elements Nb and Sn are strictly controlled to increase the hardness and wear resistance of Ti−Nb−Zr−Sn alloys, and the additional element Zr is mainly useful to improve the processability during the hot working.     

Characteristics of Diffusion Annealing Between Martensitic Stainless Steel and Nickel in the Form of Coating and Foil

Characteristics of interaction between martensitic stainless steel type AISI 410 with nickel in the form of coating layer and foil were investigated. Nickel was coated on AISI 410 substrate by electroplating in various thicknesses (6-16 μm). The 300-μm-nickel with purity of 99.9% was employed as a foil layer. All specimens were annealed in the temperature range of 700-900 °C for 5, 10, 15, and 60 min. Optical microscopy, SEM and EPMA analyzer were carried out in order to characterize the interdiffusion behavior differences between nickel and AISI 410 while using nickel layer in different form. It was observed that the thickness of nickel coating had a minor effect during annealing on the interaction between Ni and substrate at faying surface. However, the results show that the interaction of nickel coating layer with base material is much faster than foil layer during annealing process. This study suggests that the coating layer diffused faster to the substrate than foil layer; moreover, in the former case, heavy outer load was omitted. The concentration profiles were plotted for two cases. Although in case of using layer in the form of coating the annealing time was relatively short (5-15 min), it was observed that the concentration profiles for main elements had shapes close to the theoretical curve. For various thicknesses (6-16 μm) of Ni coating, the experimental results show that the interaction at faying surface caused the thickness of nickel coating growth. The diffusion zone width was plotted against the annealing temperature and time for both cases and the growth of the diffusion zones was compared.     

强磁场作用下铸造Al-4%Cu合金时效析出的

研究了强磁场对Al-4%Cu合金时效析出的影响,采用显微硬度测试、X射线衍射以及电子探针等手段研究了材料的组织及性能。结果表明:在其他条件相同情况下,强磁场提高了材料的硬度,缩短了时效析出时间并且增加了晶界析出相的数量。强磁场作用于相变时引起的时效转变扩散系数的增加是以上变化的主要原因之一。同时,结果也表明在强磁场下时效析出时基体晶粒度、脱溶相形状及其排列方式无明显变化。     

固溶处理温度对双相不锈钢在硫酸介质中腐蚀磨损行为的影响

采用销环式腐蚀磨损试验机研究了固溶处理的双相不锈钢在１０％Ｈ２ＳＯ４中的腐蚀磨损行为．腐蚀磨损率－载荷关系曲线表明：较高温度固溶的双相不锈钢在低载荷下的耐腐蚀磨损性比低温固溶的优，而在高载荷下却恰恰相反；阴极保护下（－６００ｍＶ，ＳＣＥ）具有同样的关系．扫描电镜观察证实，高温固溶处理产生大量铁素体而导致高载下出现脆性剥落是其耐腐蚀磨损性变坏的原因．     

胜利垦32区块外输管线穿孔分析与对策

胜利垦32区块外输管线频繁特殊穿孔,不易检测,治理困难。取样解剖后发现,穿孔多为手指状的直孔,几乎都由内壁点腐蚀引起。断面上穿孔分布无规律性,上中下部位均有,沿管道轴向有相对分段集中的特点。通过对腐蚀产物进行XRD分析,对腐蚀管段进行EPMA分析、材质分析以及金相检验和夹杂物检验分析,初步认定:垦32区块外输管线频繁穿孔主要是由于不同管段内表面的夹杂物分布及夹杂程度差异导致的。就试验结果和目前的技术发展来看,建议采用玻璃鳞片涂层或采用钢骨架复合管或渗氮工艺进行管线保护。     

Importance of initial surface film in the degradation of stainless steels by atmospheric exposure

The surface compositions of stainless steels types 304, 316, 430, and 444 combined with four types of surface finishes, 2B finish, hairline polishing, mirror polishing, and bright annealing, were measured by ICP-AES, EPMA, and XPS before exposure. The surface finish that most enriched the chromic species in the surface film was mirror polishing, followed by bright annealing, 2B finish, and hairline polishing. The order of corrosion-resistance was type 444, type 316, type 304, and type 430. The surface compositions were correlated with the rating number and pitting depth after exposure to atmospheric environments. The rating number had a high positive correlation with the concentration of Cr in the surface film, and had a slight correlation with the near-surface composition measured by EPMA at 12 kV, but did not show any correlation with bulk composition within the composition range covered in the present work. This same trend was observed for pitting depth. It was concluded that the cationic concentration of Cr in the surface film before atmospheric exposure is the prime factor in controlling the resistance of stainless steels to atmospheric corrosion.