304奥氏体不锈钢离子辐照后超显微硬度和微结构变化

对304奥氏体不锈钢进行固溶处理及随后的铁离子和氦离子辐照,并对三种处理试样进行超显微硬度测量和透射电镜下微观组织的观察.结果发现,相同的辐照能量和剂量下,两种离子辐照的硬化效果和微结构有较大的差异.铁离子辐照后试样的较浅层的硬化效果更显著,氦离子辐照后试样的较深层硬化效果更高些;铁离子辐照后试样表层辐照缺陷主要由高密度位错和位错缠结构成,氦离子辐照后表层辐照缺陷主要由细小致密的黑斑构成.     

应力作用下不锈钢TIG焊焊缝的He+辐照损伤行为

目的 结合核材料应用环境,探究应力作用对304奥氏体不锈钢、430铁素体不锈钢和T91马氏体不锈钢的TIG焊焊缝辐照损伤行为的影响.方法 采用剂量(每cm2的离子数量)为2.1×1017,辐照能量为150 keV,束流为60μA的He+离子束,对2种应力状态下3种不锈钢的焊缝进行He+辐照,并对其辐照前后的微观形貌和显微硬度进行测试分析.结果 SEM图像表明,外加拉应力的引入对304奥氏体不锈钢焊缝辐照缺陷的密度分布和尺寸大小的影响最大,辐照缺陷的间距在有应力作用时缩小了61.5％,缺陷的尺寸则增长了59.2％;纳米压痕数据显示,外加拉应力对T91马氏体不锈钢辐照硬化率增长的影响相对较小,仅为17.9％.结论 应力会使辐照缺陷最大尺寸增加,应力会在一定程度上降低材料的抗辐照性能.辐照导致T91,304,430这3种不锈钢焊缝硬度提高.相同应变条件下,与430不锈钢和304不锈钢相比,T91钢焊缝辐照硬化增量最小,T91焊缝的抗辐照硬化性能相对优异,工程应用中可优先选用T91钢.     

He+ 辐照对CLAM钢焊缝微观组织和性能的影响

在室温下用强度为70 keV的He⁺辐照CLAM钢焊缝,使用扫描电子显微镜(SEM)、透射电子显微镜(TEM)和连续刚度纳米压痕技术(CSM)对其表征,研究了He⁺辐照对CLAM钢焊缝的微观组织和性能的影响。结果表明,随辐照剂量的增大焊缝表面黑色孔洞的尺寸增大、密度提高;辐照剂量为1×10¹⁷ ions·cm^-2时,在两种焊缝中形成的位错环的尺寸分别约为18.97 nm、15.73 nm,数密度分别约为2.24×10²¹ m^-3、1.78×10²¹ m^-3,氦泡引起的辐照肿胀率分别约为1.7%和0.4%;辐照缺陷(位错环、氦泡)导致的辐照硬化率分别为49.0%和29.9%。与焊态焊缝相比,调质处理态焊缝的辐照损伤较弱,在一定程度上表明经调质处理后焊缝的抗辐照性能有所提高。     

奥氏体不锈钢离子渗碳后的腐蚀行为

为了提高奥氏体不锈钢零件的使用寿命,利用低温离子渗碳技术对AISI 316L奥氏体不锈钢进行了表面渗碳处理.用X射线衍射仪和光学显微镜分析了渗碳层的微观组织结构,用显微硬度计测试了渗碳层的硬度分布,通过电化学极化曲线测试技术和化学腐蚀试验研究了离子渗碳AISI 316L不锈钢的腐蚀行为.渗碳层为单相碳过饱和奥氏体固溶体,由此明显提高了AISI 316L不锈钢的抗腐蚀性能,渗碳层硬度梯度平缓,表面显微硬度高达900 HV.结果表明,奥氏体不锈钢低温离子渗碳处理不仅提高了其表面硬度,而且提高了不锈钢表面的耐腐蚀性能,从而提高了其使用寿命.     

奥氏体不锈钢焊接接头辐照偏析和辐照硬化的研究

为探究奥氏体不锈钢焊接接头辐照后的晶界偏析和硬化规律,实验采用剂量为2×10~(17)n/cm~2、100 keV的He~+对三组不同焊接参数的316L焊接接头进行辐照,并对其辐照前后的硬度、微观结构和晶界成分进行了表征。辐照后焊接接头的TEM结果表明出现了位错环、位错缠结、位错墙、位错胞和氦泡等辐照诱导的特征微结构,但其尺寸和密度与焊接参数并无明显的关联;晶界的EDS数据表明,辐照诱导的偏析会导致焊缝原本富Cr贫Ni的晶界出现富Ni贫Cr的现象;辐照前后的显微硬度数据表明,辐照后硬度的增量随着热输入增大而减小。因此,奥氏体不锈钢焊接接头辐照偏析和辐照后显微结构的变化与普通奥氏体不锈钢类似;晶粒尺寸随着焊接热输入减小而减小,而晶粒细化使晶粒内位错通道密度增大,辐照产生的高密度缺陷对位错滑移的阻碍作用就越明显,则辐照硬化增量会随着热输入的增大而减小。     

同位素效应对铁中辐照损伤的影响

有关氦与辐照缺陷的相互作用已有不少系统性的工作,但对氢与辐照缺陷的相互作用的研究不多。特别是氢的同位素氘或者氚存在于核聚变反应堆中,关于氢的同位素效应对辐照损伤的研究工作很少。采用离子加速器在室温下对纯铁注入氘离子,经500℃时效1h后,研究了电子辐照下位错环的演变过程并讨论了同位素效应对位错环偏压的影响。实验表明,随辐照剂量的增加,空位型位错环的尺寸逐渐减小直至消失。由于注氘纯铁中的位错偏压小,其空位型位错环缩小的速率比注氢纯铁中空位型位错环小,由此可以推断注氘纯铁比注氢纯铁抗辐照损伤性能好。     

坡口形状对CLAM钢焊缝抗辐照损伤性能的影响

为探究坡口形状对中国低活化马氏体(CLAM)钢焊缝辐照损伤性能及辐照硬化性能的影响,采用扫描电子显微镜(SEM)、原子力显微镜(AFM)、透射电子显微镜(TEM)、掠入射X射线衍射(GIXRD)和纳米压痕技术等方法,研究了在室温下经能量为70 keV、剂量为1×10¹⁷ions/cm²的He⁺辐照后,V型、U型和双U型坡口CLAM钢焊缝的辐照损伤情况及力学性能。结果表明,离子辐照后,不同坡口形状焊缝金属中均产生了氦泡、析出物等缺陷,力学性能呈现出不同程度的降低。与V型和U型坡口焊缝相比,双U型坡口焊缝辐照后焊缝内部缺陷分布更均匀、尺寸更小。这是由于在三类焊缝中,双U型坡口焊缝热输入更小,焊缝晶粒组织相对较小,晶界密度更高。更高密度的晶界阻碍了缺陷间的相互聚集,减小了缺陷的尺寸。辐照后双U型坡口焊缝表面粗糙度最低,氦泡、析出物尺寸最小,衍射峰偏移量、宽化率最低,表面硬度最低,抗辐照硬化性能最好。这表明通过控制焊接坡口的形状,细化焊缝晶粒组织,可显著提升焊缝抗辐照损伤性能及抗辐照硬化性能。     

脉冲电流处理对轧制316L不锈钢的快速强化

目的 探究不同参数的脉冲电流处理(EPT)对轧制316L不锈钢拉伸性能、显微硬度及微观组织的影响。方法 将轧制的316L不锈钢作为原始样,调节流过样品的脉冲电流密度,分别为130、170、190、260、310 A/mm²,分析脉冲电流密度与其拉伸性能和显微硬度的关系。结果 轧制316L不锈钢的抗拉强度和显微硬度随着脉冲电流密度的增大呈现先增大后减小的趋势,其中当脉冲电流密度为170 A/mm²时达到峰值,抗拉强度由1 485 MPa提升到1 625 MPa,同时显微硬度也由431HV增大到473HV。通过电子背散射衍射分析微观组织可知,与原始样相比,经过脉冲电流处理的样品晶粒尺寸明显减小,马氏体含量明显增多,脉冲电流处理可以促使微观组织快速均匀化。结论 脉冲电流处理可以在短时间内实现轧制316L不锈钢组织的均匀化调控,有效改善轧制316L不锈钢的微观组织,减少轧钢形变织构,促使参与的奥氏体转变为马氏体,使微观组织趋于稳定,同时还可以使轧制316L不锈钢晶粒快速细化,达到细晶强化的效果,有效提高整体抗拉强度和显微硬度。     

316L/S32101异种金属焊接接头的显微组织与力学性能研究

目的 研究乏燃料水池用钢板316L与覆板S32101双相不锈钢的焊接性、接头不同区域显微组织特征及接头与母材之间的性能差异.方法 利用氩弧焊接技术对5 mm厚的316L底板与3 mm厚的S32101覆板以搭接的形式进行焊接,利用金相显微镜、扫描电镜、维氏显微硬度仪和电子万能材料试验机对焊接接头的宏观形貌、显微组织以及力学性能进行研究.结果 316L/S32101焊缝组织主要由铁素体基体、晶界树枝状奥氏体以及晶内细小片状奥氏体所组成;316L侧靠近焊缝处存在一个较窄的熔合区,其组织由奥氏体基体和少许细小分散的铁素体组成,而S32101侧靠近焊缝处组织则由粗大铁素体晶粒和沿晶粒边界分布的若干小块状奥氏体组成.从316L母材区到焊缝区,硬度显著增大,而从焊缝区到S32101母材区,硬度变化很小;焊接接头的抗拉强度高达510 MPa,为两侧316L和S32101母材强度的87.9％和88.6％.结论 在焊接电流为240 A和焊接速度为300 mm/min的条件下,可以通过氩弧焊获得成形良好的搭接接头,且接头的力学性能优异.     

纳米二氧化钛对质子辐照下MQ增强硅橡胶力学性能的影响

采用空间综合辐照模拟设备研究了纳米二氧化钛对100 keV和150 keV能量质子辐照下MQ增强加成型硅橡胶力学性能的影响。试验结果表明,质子辐照后,未添加纳米粒子的硅橡胶表面颜色明显加深,同时出现不同程度的老化龟裂裂纹,裂纹数量和深度随辐照能量和剂量的增加而增加;硅橡胶的硬度和拉伸强度随辐照剂量的增加先增加而后降低。添加纳米二氧化钛的硅橡胶与未改性硅橡胶相比,经过相同能量、剂量的质子辐照后,表面颜色加深和表面裂纹损伤的程度均减小,硬度和力学性能的损伤程度下降,表现出明显的抗质子辐照性能。     

Evaluation of variation of tensile strength across 316LN stainless steel weld joint using automated ball indentation technique

Tensile strength variation across 316LN stainless steel fusion welded joint comprising of base metal, deposited weld metal and heat affected zone (HAZ) has been evaluated by Automated Ball Indentation (ABI) technique. Automated Ball Indentation tests were conducted on the various zones of the steel weld joint at 300, 523 and 923?K. The flow curves obtained from ABI results were consistent with corresponding conventional uniaxial tensile test results. The HAZ exhibited higher tensile strength than the other regions of the steel weld joint at all investigated temperatures. The ratio of ultimate tensile strength to yield stress (YS), which represents the work hardening behaviour, increased with an increase in temperature for the base metal and HAZ; whereas it remained nearly the same for the weld metal.     

Experimental investigation on corrosion and hardness of ion implanted AISI 316L stainless steel

The AISI 316L stainless steel has been widely used both in artificial knee and hip joints in bio-medical applications. In the present study AISI 316L SS was implanted with two different ions: nitrogen and helium at 100 keV with a dose of 1 × 10¹⁷ ions/cm² at room temperature. The crystallographic orientation and surface morphology were studied using X-ray diffraction (XRD) and scanning electron microscope (SEM). The effects of ion implantation on the corrosion performance of AISI 316L stainless steel was evaluated in 0.9% NaCl solution using electro chemical test both on the virgin and implanted samples. The subsequent Tafel analysis shows that the ion implanted specimens were more corrosion resistant when compared to the bare specimens. Microhardness was also measured by Vickers method by varying the loads. The results of the studies indicated that there was a significant improvement in both corrosion resistance and hardness of implanted samples.     

强流脉冲电子束对4Cr13不锈钢的表面改性

为了改善4Cr13不锈钢的表面强度和耐磨性,对其进行了强流脉冲电子束表面辐照处理,研究了该处理对4Cr13的形貌、相结构、显微硬度及耐磨性能的影响。结果表明：电子束处理后,不锈钢表面出现多种形态的熔坑,20次脉冲处理时熔坑边缘出现了大量的变形孪晶;脉冲电子柬处理使不锈钢发生了由α相向γ相的转变,表层晶粒细化至纳米尺度;...     

Investigation on microstructure,mechanical properties and corrosion behavior of AISI 316L stainless steel to ASTM A335-P11 low alloy steel dissimilar welding joints

In the present study, the microstructure, mechanical properties and corrosion resistance of AISI 316L austenitic stainless steel to ASTM A335-P11 low alloy steel dissimilar joints, which are widely employed in the oil and gas industries especially for manufacturing of heat exchangers over 600°C, were investigated. For this purpose, two filler metals of ER309L and ERNiCrMo-3 were selected to be used with GTAW process. The results of microstructural evaluation revealed that the ERNiCrMo-3 weld metal contains dendritic and interdendritic zones, and the ER309L weld metal microstructure includes skeletal ferrites in an austenitic matrix. The maximum impact fracture energy and microhardness values were obtained for the ERNiCrMo-3 weld metal specimens; however, no significant difference was observed between the tension properties. The corrosion test results showed that the ERNiCrMo-3 has a higher corrosion resistance than ER309L. Finally, it was concluded that ERNiCrMo-3 would be a suitable filler metal for joining AISI 316L to A335-P11 for a variety of applications.     

304不锈钢管TIG焊接头凝固行为及热力耦合研究

目的 对2mm厚不锈钢管的焊接工艺参数进行优化,并基于模拟仿真软件对接头的热应力场进行模拟,以解决薄壁管件接头应力测试不方便的问题。方法 以TIG焊对2 mm不锈钢管进行焊接,通过对接头宏观形貌、微观组织、显微硬度等结果进行优化进而得到最佳焊接工艺参数,采用双椭球热源和温度-位移耦合方法结合最优工艺参数进行数值模拟。结果 当焊接电流为150 A、焊接速度为66 cm/min时,焊接接头全部熔透,且正面及背面焊道均匀致密,成形良好。焊缝中心上部区域和下部区域均呈现等轴晶形貌,下部区域尺寸较上部区域尺寸略大,熔合线附近为柱状晶组织。焊接接头显微硬度整体分布呈现U形,其中热影响区显微硬度（197HV）大于焊缝区域硬度（162HV）,熔合线附近显微硬度达到最低值（145HV）。模拟结果显示,在焊接过程中,当纵向残余应力从母材向焊缝中心过渡时,由压应力逐步转化为拉应力;焊缝中心横向应力呈现为压应力,向两侧母材过渡时应力值逐渐趋近于0,径向应力值变化幅度较小,模拟数据变化趋势与实测数据变化趋势接近。     

Keyhole gas tungsten arc welding of AISI 316L stainless steel

Keyhole gas tungsten arc welding (K-TIG) was used to weld AISI 316L stainless steel of mid-thickness (thickness ranging 6–13 mm). 316L plates of 10-mm thickness were jointed using an I-groove in a single pass without filler metal. The effects of welding parameters on the fusion zone profile were investigated. The weld properties, including mechanical properties, microstructure, and corrosion resistance, were analyzed. The primary weld microstructures were austenite and δ-ferrite. The tensile strength and impact property of the weld were almost the same as those of the base metal, while the corrosion resistance of the weld was even better than that of the base metal. High-quality 316L stainless steel joints can be realized through K-TIG welding with high productivity and low processing cost. The practical application of K-TIG welding to join mid-thickness workpieces in industry is well demonstrated and an ideal process for welding AISI 316L of mid-thickness with high efficiency and low cost is presented.     

A study on low magnetic permeability gas tungsten arc weldment of AISI 316LN stainless steel for application in electron accelerator

Low magnetic permeability is an important criterion in selection of the material of construction of beam pipes and vacuum chambers of electron accelerators for safeguarding against distortion of the magnetic field. In the modified design of new 20 MeV/30 mA Injector Microtron for the existing synchrotron radiation sources Indus-1 and Indus-2, AISI 316 LN stainless steel has been identified as the material of construction of its vacuum chamber. Welding of AISI 316LN stainless steel with conventional filler alloys like ER316L and ER317L of AWS A5.9 produces duplex weld metal with 3–8% ferro-magnetic delta ferrite to avoid solidification cracking. The results of the study has demonstrated that GTAW of AISI 316LN SS with high Mn adaptation of W 18 16 5 N L filler produced a crack free non-magnetic weld with acceptable mechanical properties. Moreover, AISI 316LN stainless steel is not required to be solution annealed after the final forming operation for obtaining a low magnetic permeability, thereby avoiding solution annealing of large vacuum chamber in vacuum/controlled atmosphere furnace and associated problems of distortion. Besides Injector Microtron, the study also provides useful input for design of future indigenous accelerators with vacuum chambers of austenitic stainless steel.     

Multiple heat isothermal stress rupture correlations for type 316L(N) stainless steel and their use Part 2 – Applications for nuclear grade type 316L(N) stainless steel base metal and its weld metal

Abstract

The 'reference' multiple heat isothermal stress rupture correlations for stainless steel types 316 and 316L(N) base metals derived in Part 1 are used for establishing those for a specific 316L(N) stainless steel base metal and also its weld, both candidates for the forthcoming prototype fast breeder reactor at Kalpakkam. The phases that form in the weld metal during creep are the same as those in the base metal; however, the uniformly distributed δ ferrite ( ~ 7 ferrite number) in vermicular morphology present in the initial microstructure accelerates their formation and increases their quantities, resulting in poorer stress rupture properties. A simple modification allows for correlating and extrapolating the weld data to long rupture lives using the multiple heat isothermal correlations developed for the base metal.