微观组织对0Cr17Ni4Cu4Nb马氏体不锈钢的耐点腐蚀性能的影响

采用化学浸泡法和模拟闭塞电池方法研究了固溶+时效和固溶+调整+时效处理的0Cr17Ni4Cu4Nb马氏体不锈钢的耐点腐蚀性能,并与18-8型奥氏体不锈钢(316L)耐点蚀性能进行了对比。结果表明,0Cr17Ni4Cu4Nb马氏体不锈钢组织内富Cu析出相促进了点蚀坑萌生,而点蚀坑发展则与组织形貌有关。固溶+调整+时效处理的0Cr17Ni4Cu4Nb马氏体不锈钢因组织内析出富Cu相多而大,其萌生的点蚀坑密度较高,但由于马氏体板条较细,其点蚀坑尺寸和深度较小;固溶+时效处理的0Cr17Ni4Cu4Nb马氏体不锈钢因组织内析出富Cu相少而小,萌生的点蚀坑密度较低,但粗大的板条马氏体组织导致点蚀坑尺寸和深度较大。与18-8型奥氏体不锈钢耐点蚀性能对比表明,通过对0Cr17Ni4Cu4Nb马氏体不锈钢进行合理的热处理,其耐点蚀性能可与18-8型奥氏体不锈钢相当。     

不锈钢与渗碳钢惯性摩擦焊接头的组织与性能

目的 研究0Cr18Ni12Mo2Ti不锈钢与20CrMnMo渗碳钢的惯性摩擦焊焊接接头的组织与力学性能。方法 通过金相、能谱分析、显微硬度、拉伸试验对焊接接头进行组织与力学性能分析。结果 焊接试样上0Cr18Ni12Mo2Ti不锈钢一侧飞边尺寸比20CrMnMo渗碳钢一侧飞边小;焊接接头熔合区仅为50 μm,熔合线附近元素扩散层很窄,其中0Cr18Ni12Mo2Ti不锈钢仍为奥氏体组织,20CrMnMo钢组织由铁素体与珠光体转变为马氏体与索氏体,20CrMnMo一侧热力影响区组织为细小的片状珠光体与铁素体;焊缝区的显微硬度为358HV,高于2种母材;焊接接头抗拉强度大于590 MPa,断后伸长率大于32%,断裂位置均在0Cr18Ni12Mo2Ti不锈钢母材一侧。结论 采用惯性摩擦焊工艺可实现不锈钢与渗碳钢的高强连接。     

Fe-16Cr-2.5Mo合金悬臂梁减振性能的研究

从解决工程应用问题出发,分别利用加速度传感器与应变传感器,在20 Hz～400 Hz范围内,采用相同的实验方法对比研究了0Cr18Ni9Ti不锈钢、1 100°C退火态与冷轧态Fe-16Cr-2.5Mo合金悬臂梁在宽频带激励下的减振性能.研究结果表明,热处理对Fe-16Cr-2.5Mo合金梁的减振性能有很大的影响, 自由振动下退火态悬臂梁的振动加速度和应变衰减较冷轧态与0Cr18Ni9Ti不锈钢显著;受迫振动下退火态悬臂梁的振动加速度峰值与应变峰值较0Cr18Ni9Ti不锈钢与冷轧态有明显的下降.     

热处理对0Cr1 7Mn14Mo2N双相不锈钢性能的影响

研究了热处理对0Cr17Mn14Mo2N双相不锈钢铸态组织中δ－铁素体的含量，形态以及双相不锈钢性能的影响。结果表明，在1050－1200℃之间加热时，组织为奥氏体基础上分布着的球化的及长条形的δ－铁素体，且加热温度越高保温时间越长铁素体的球化率越高。在1250℃加热时，组织为粗大的铁素体等轴晶，其中铁素体以球状均匀分布的0Cr17Mn14Mo2N双相不锈钢的拉伸性能最好。     

稀土对1Cr18Ni9钢腐蚀性能及组织状态影响

利用化学法对1Cr18Ni9钢表面扩渗稀土,通过X－射线衍射分析了试样表面的组织状态。结果表明,1Cr18Ni9钢渗入稀土后,表面有CeFe7和LaO新相产生,并引起奥氏体含量降低,铁素体含量增加,改变了试样表面的微观结构。阳极极化曲线的测定结果表明,扩渗稀土后的1Cr18Ni9钢试样耐腐蚀性能超过了稳定化处理的1Cr18Ni9Ti钢水平。     

珠光体耐热钢与奥氏体不锈钢的焊接

奥氏体不锈钢(1Cr18Ni9Ti)和珠光体耐热钢(12Cr12Mo)焊接时,用在珠光体耐热钢的坡口表面堆焊过渡层或附加中间过渡段的方法,可以得到奥氏体和少量铁素体的双相组织的焊缝,焊接接头在500℃以上的条件下工作,提高焊接接头的热持久强度,取得较好的使用效果。     

关于隔离开关各种常见故障的分析及措施

奥氏体不锈钢(1Cr18Ni9Ti)和珠光体耐热钢(12Cr12Mo)焊接时,用在珠光体耐热钢的坡口表面堆焊过渡层或附加中间过渡段的方法,可以得到奥氏体和少量铁素体的双相组织的焊缝,焊接接头在500℃以上的条件下工作,提高焊接接头的热持久强度,取得较好的使用效果。     

冷却速率对1Cr18Ni9Ti钢高温脆性区凝固组织的影响

连铸过程中裂纹主要产生在凝固末期的高温脆性温度区间,凝固组织对其影响巨大.结合相图并利用示差扫描量热仪(DSC)、定向凝固实验系统和Gleeble-3800热模拟实验机,在对1Cr18Ni9Ti奥氏体不锈钢的熔化和近平衡凝固过程进行分析的基础上,研究了冷却速率对奥氏体不锈钢高温脆性区凝固组织的影响.研究表明,1Cr18Ni9Ti钢的近平衡凝固模式为FA型,随着冷速的加大,铁素体的形态从晶内骨骼状分布转变到晶间不规则块状分布,其含量也有所提高.     

飞机发动机用梯度封严涂层的研究

为了进一步提高封严涂层与基体材料之间的附着性能,对梯度封严涂层与1Cr18Ni9Ti不锈钢之间的附着性能进行了探讨。采用拉开法测试梯度封严涂层与1Cr18Ni9Ti不锈钢之间的附着强度,并用冷热循环法测试梯度封严涂层的耐冷热循环性能,与普通封严涂层的附着强度及耐冷热循环性能进行比较,结果发现：梯度封严涂层的附着强度比普通封严涂层的附着强度有提高,而且梯度封严涂层的耐冷热循环性能明显优于普通封严涂层。     

铁素体对铸造奥氏体不锈钢CF-3M性能的影响

研究了铁素体含量对铸造奥氏体不锈钢CF 3M的强度、磁性能的影响 ,结果表明 ,调整Cr、Ni当量比值可以控制铁素体含量 ,从而可以调整钢的强度和磁性能。随Cr、Ni当量比值的增加 ,钢中铁素体含量增加 ,钢的强度也随之增加 ,磁导率增加的速率加快。但铁素体含量以不超过 7%为宜 ,即Cr、Ni当量比值应小于 1.0 2。     

A new constitution diagram for predicting ferrite content of stainless steel weld metals

Duplex stainless steels combine the best properties of austenitic and ferritic stainless steels. They possess high yield strengths (=450 N/mm²) and have excellent resistance to stress corrosion cracking in severe corrosive environments. The secret of this optimum combination of properties is the balanced austenite-ferrite microstructure of the alloys and the weld metals used to join them. The High Alloys Committee of the US-based Welding Research Council has recently issued a new constitution diagram to assist the prediction of the ferrite content of duplex stainless steel weld metals from the alloy's chemical composition.     

Struktur und Eigenschaften nichtrostender Stähle nach einer Plasmaimmersionsionenimplantation und einer Plasmanitrierung

Structure and properties of stainless steels after plasma immersion ion implantation and plasma nitriding Stainless steels can be nitrided at temperatures ≤ 400 °C to increase their hardness and wear resistance without a decreasing of their excellent corrosion resistance. Structure and properties of the surface layers produced by plasma nitriding and plasma immersion ion implantation in this temperature range were tested. There are negligible differences in the structure of the produced surface layers in spite of different interaction principles of the used technologies. However there are clear differences between the case of different steels. The case of ferritic chromium steels mainly consists of ε-nitride. Whereas the cases of austenitic and ferritic austenitic steels are characterized by expanded austenite. The corrosion resistance of the steels is reduced by nitriding only, if evident CrN-formation occurs.     

Electrochemical corrosion behavior of novel Cu-containing antimicrobial austenitic and ferritic stainless steels in chloride media

The electrochemical corrosion behavior of novel Cu-containing antibacterial austenitic and ferritic stainless steels in 0.05 mol/L NaCl solution has been investigated by dc polarization and ac impedance measurements and compared with that of the conventional stainless steels. Cu was found to particularly affect the kinetics of the anodic reaction. The corrosion performance of the austenite was greatly improved by Cu addition in the studied anodic potential range, whereas Cu effects on the ferrite showed remarkable sensitivity to the applied potential and improved corrosion resistance only in the low anodic potential range. Three-dimensional presentation of the variable-potential impedance data was employed in analyzing the electrochemical corrosion processes and revealed a close relationship between the impedance parameters and the applied potential. The trends of impedance results agree well with those obtained from potentiodynamic polarization measurements.     

Sintering and characterization of YAG dispersed ferritic stainless steels

The present study investigates the effect of yttrium aluminium garnet (YAG) addition on the densification, mechanical, tribological and corrosion behaviour of ferritic (434L) stainless steels. The composites were sintered at both solid-state (1200 °C) and supersolidus (1400 °C) sintering conditions. Supersolidus sintering results in superior densification, hardness and corrosion resistance of both straight 434L stainless steel as well as YAG reinforced 434L stainless steels. The addition of YAG to 434L stainless steels at supersolidus sintered conditions improves the strength and wear resistance of 434L stainless steels without significantly degrading the corrosion performance.     

Structure and properties of ion-nitrided stainless steels

The structure and properties of ion-nitrided layers on several stainless steels, 410 martensitic stainless steel, 430 ferritic stainless steel and 321 austenitic stainless steel, has been studied under varying process conditions with microhardness-depth correlations, optical microscopy and transmission electron microscopy. The process variables studied include time (2 to 10 h) and temperature (400 to 600° C). The highest case depth values and hardness levels were observed in martensitic stainless steels. The lowest case depths were observed in austenitic stainless steel. In general, the behaviour of matensitic and ferritic stainless steels were similar. All three steels showed increasing case depths and decreasing surface hardnesses with increasing ion-nitriding temperatures and times. Nitriding depth was found to be parabolic with ion nitriding time in all three steels at all ion-nitriding temperatures investigated, the nitriding reaction being faster in martensitic stainless steel than the others. Electron microscopy showed that almost no structural difference arises in the core of ferritic and austenitic stainless steels whereas recrystallization of the martensitic structure was observed in the core of martensitic steel following ion nitriding. Electron microscopy results also showed that ion nitriding produces platelets or disc-shaped precipitates on {001} matrix planes, coherent with the matrix. These platelets showed a striated morphology which is thought to be the result of the elastic strain in the matrix.     

Development of high nitrogen, low nickel, 18%Cr austenitic stainless steels

Two high nitrogen stainless steels are studied through metallographic, mechanical and corrosionistic tests and the results are compared with those shown by a standard AISI 304. These high nitrogen steels show a significantly higher mechanical strength than usual AISI 304 while their corrosion resistance lie among that of standard austenitic and that of standard ferritic stainless steels.     

Zum Verhalten rost‐ und säurebeständiger Stähle unter Komplexbeanspruchung. Teil 1 Passivität und Lochkorrosionsbeständigkeit

Some Aspects on Corrosion Fatique of Stainless Steels. Part 1 Passivity and Pitting Corrosion Susceptibility Iron‐Chromium‐Nickel alloys are of special interest for many applications because of their excellent resistance to corrosion. The nature and composition of passive films formed on stainless steels depend on the prevailing conditions, viz. steel‐composition, passivation potential, aging, pH, electrolyt composition and temperature. Passive films may be damaged by local breakdown. At least two mechanisms are possible for this localisation: mechanical breakdown by slip steps and electrochemical breakdown (for e.g. by the effects of chloride ions). Because of this, steels suffer a degradation of their fatique properties when exposed to an aqueous environment. Passivation of austenitic, ferritic‐austenitic and martensitic stainless steels has been studied in different solutions using electrochemical techniques. The results clarified that for two of the investigated alloys the prediction of fracture initiation based on pitting corrosion in chlorid containing solutions is possible. (To be continued.)     

Methods to overcome embrittlement problem in 9Cr–1Mo ferritic steel and its weldment

This article presents the issues that need to be addressed in ferritic steel, for their use in nuclear core, namely, the embrittlement and type IV cracking of weldment. It has been established that the ferritic steels possess a significantly higher resistance to radiation damage as compared to the present generation austenitic stainless steels and the creep behavior is satisfactory for applications up to 873 K. The major challenges that need to be addressed are the poor creep resistance of the weld joints and embrittlement of ferritic steels. This article describes the efforts taken at IGCAR to overcome the embrittlement problem by impurity control, grain boundary engineering or design of suitable thermomechanical treatments in a 9Cr–1Mo ferritic steel.     

铁素体不锈钢在高温尿素环境中的腐蚀行为研究

对三种商用车排气系统用铁素体不锈钢(436L、439M、441)进行了尿素结晶腐蚀试验,以模拟铁素体不锈钢在商用车排气系统内选择性催化还原器(SCR)中的渗氮腐蚀行为。探究了合金成分及夹杂物对不锈钢耐高温尿素腐蚀的影响,并依据EDS表征结果阐释了材料内部腐蚀的渗氮机理。研究表明,在高温热震疲劳和氧化的协同作用下,高温高氮的环境导致铁素体不锈钢晶界及晶内局部区域快速析出氮化铬颗粒,造成晶界及基体局部区域贫铬。由于436L和441不锈钢含有较高的Mo和Nb,其耐高温尿素腐蚀能力显著优于439M。此外,由于436L和441不锈钢中夹杂物细小弥散,也降低了氮化铬在夹杂物的形核析出几率,成为提高抗高温尿素腐蚀的另一个因素。