Assessing mechanical properties of the dissimilar metal welding between P92 steels and alloy 617 at high temperature

In this study, a new welding technology of dissimilar materials, Cr-based P92 steels and Ni-based Alloy 617 is introduced and demonstrated to investigate its reliability. Firstly, multi-pass dissimilar metal welding between P92 steel and Alloy 617 was performed using DCEN TIG welding technology, buttering welding technique and a narrow gap groove. After welding, in order to understand characteristics of the dissimilar metal welds, metallurgical micro-structures analysis by optical observation and static tensile strength assessment of the dissimilar welded joints were conducted at 700°C.     

Assessment of the crack growth characteristics at the low fatigue limit of a multi-pass welded Ni-based alloy 617

It has become known that the most effective methodology for green power plant systems is to increase the generating efficiency of steam power plants. Among the materials developed to improve the performance, it is known that the most practical and applicable materials are Ni-based Alloys. However, it is necessary to first guarantee mechanical reliability of the weld for applying these Ni-based Alloys. In this study, firstly, the fatigue strength of multi-pass welded Ni-based Alloy 617 in as-welded and post weld heat-treated conditions were assessed. And then the crack growth characteristics at the low fatigue limit of them were assessed. From the results, fatigue strength of the welds those were post weld heat treated did not show large difference compare to not heat-treated ones. These results mean that the weld of Ni-based Alloy 617 is not influenced remarkably by post weld heat treatment in the metallurgical and mechanical changes. However, it was found that the fatigue crack grew at the low fatigue limit, which was about 48.4% (327 MPa) of the static tensile strength (675.1 MPa) of the weld, and 43.1% of the base material (759.4 MPa).     

新的多轴非比例加载低周疲劳寿命估算公式

利用对 3 16L不锈钢多轴非比例加载低周疲劳的试验结果 ,对现有的多轴低周疲劳寿命估算方法进行讨论 ;基于 3 16L不锈钢非比例加载低周疲劳的微观机理 ,选择最大剪应变以及应变路径的非比例度作为损伤参量 ,建立基于临界面方法的新的非比例加载低周疲劳寿命估算公式 ;利用新的非比例加载低周疲劳寿命估算公式对寿命的预测结果表明 ,新的寿命估算公式对剪切型破坏的 3 16L与 3 16LN不锈钢及拉伸型破坏的 3 0 4不锈钢非比例加载低周疲劳寿命预测精度比现有的临界面方法高     

Q355NE+SUS304异种金属焊接接头组织与腐蚀疲劳性能研究

以Q355NE+SUS304异种金属焊接接头为研究对象,对其显微组织、3.5%NaCl+0.5%Na2SO4(质量分数),PH=5溶液腐蚀疲劳和腐蚀疲劳断裂特征进行了研究,分析了异种金属焊接接头腐蚀疲劳性能和断裂过程。结果表明:试验级腐蚀疲劳极限在170MPa左右,腐蚀疲劳裂纹起源于Q355NE侧的热影响区,逐渐扩展最终断裂于接头焊缝区,异种金属焊接接头构件级腐蚀疲劳通过4吨极限加载条件下的200万次试验,未发生破坏。     

基于微观孔洞型损伤的疲劳蠕变寿命预测方法

孔洞型损伤是延性金属材料一种常见的破坏形式.对于材料疲劳蠕变破坏过程,文中提出等效孔洞体积概念,从微观唯象角度出发,综合考虑疲劳蠕变对孔洞体积长大的影响,得到一种微孔洞型疲劳蠕变寿命预测模型.以此模型对1.25Cr0.5Mo钢540℃应力控制下疲劳蠕变寿命进行预测,结果显示该模型具有很好的适用性.     

Preliminary application of the draft code case for alloy 617 for a high temperature component

The ASME draft Code Case for Alloy 617 was developed in the late 1980s for the design of very-high-temperature gas cooled reactors. The draft Code Case was patterned after the ASME Code Section III Subsection NH and was intended to cover Ni-Cr-Co-Mo Alloy 617 to 982°C (1800°F). But the draft Code Case is still in an incomplete status, lacking necessary material properties and design data. In this study, a preliminary evaluation on the creep-fatigue damage for a high temperature hot duct pipe structure has been carried out according to the draft Code Case. The evaluation procedures and results according to the draft Code Case for Alloy 617 material were compared with those of the ASME Subsection NH and RCC-MR for Alloy 800H material. It was shown that many data including material properties, fatigue and creep data should be supplemented for the draft Code Case. However, when the evaluation results on the creep-fatigue damage according to the draft Code Case, ASME-NH and RCC-MR were compared based on the preliminary evaluation, it was shown that the Alloy 617 results from the draft Code Case tended to be more resistant to the creep damage while less resistant to the fatigue damage than those from the ASME-NH and RCC-MR.     

Corrosion and erosion performance of HVOF/TiAlN PVD coatings and candidate materials for high pressure gate valve application

The main objective of this paper is to study the slurry erosion and corrosion behavior of WC10Co4Cr, Armcore ‘M’ Stellite 6 and 12 HVOF coatings, TiAlN PVD coating, selected steels, such as X20Cr13, 17Cr–4Ni pH steel and Ti6Al4V titanium alloy alongwith conventional hard weld deposits of Stellite 6 and 21. The slurry erosion studies were carried out at 60° angle of impingement for the velocities in the range of 15–20 m/s using mineral sand of −40 to +80 mesh. The corrosion studies were carried out as per ASTM B 117-73 for 100 h. During slurry erosion testing, WC10Co4Cr HVOF along with TiAlN PVD coating are found out, to be the best coating materials followed by HVOF coating of Armcore ‘M’ material. However, for corrosion, Ti6Al4V, Stellite 6 and 21 hard weld deposits and 17Cr–4Ni pH steel turned out to be the best materials followed by HVOF coating of Stellite 6 and 12. HVOF coatings of WC10Co4Cr and Armcore ‘M’ materials corroded significantly, however, TiAlN PVD coating corroded very badly even after 24 h of testing.     

在役压力容器含缺陷结构腐蚀疲劳剩余寿命预测的随机分析

本文根据OCr18Ni9钢在1000ppm NaCl溶液中的腐蚀疲劳裂纹扩展速率计算公式，采用概率方法，考虑裂纹尺寸、载荷、材料等参数的随机性，给出腐蚀疲劳剩余寿命随机计算方法。最后，通过工程案例说明方法的可行和有效。     

Investigation of the fatigue behaviour of butt-welded joints treated by ultrasonic peening process and compared with fatigue life assessment standards

Ultrasonic peening is a technique to be used for improving the fatigue life of welded structures. The technique makes use of an ultrasonically vibrated pin which is pressed against the toe regions of the weld. The beneficial effect is mainly due to the introduction of favourable compressive stresses on weld toe regions, causing local plastic deformation and reducing stress concentration effect. This paper deals with the influence of ultrasonic peening treatment on fatigue life improvement in butt-welded plates. Fatigue life is predicted for the welded plate as per BS 7608 standard, AWS D 1.1 structural welding code and IIW-XIII-1539-96 standard, and they are compared with the experimental results. The ultrasonic peening technique is applied on a plain carbon steel plate weldment, and specimens conforming to ASTM E 466 standard are prepared and tested in a servohydraulic static dynamic testing machine at three different stress levels. Afterwards their fatigue lives are obtained. The comparison of the fatigue life in unpeened and peened specimens brings out the beneficial influence of the treatment. It is found that the improvement in fatigue life is up to 35% at 250 MPa of applied stress. But at higher stress levels, the benefit is less. At 350 MPa of applied stress, peening results in lower fatigue life. A comparison of the predicted fatigue lives from various standards with the experimental results shows that it is very close to the life at 50% probability of survival as predicted by the BS 7608 standard. The details of the experiments conducted and the results obtained are furnished in this paper.     

不锈钢波纹管在NaCl溶液中腐蚀疲劳寿命试验

研究了不锈钢波形膨胀节的腐蚀疲劳寿命,在3.5%NaCl溶液的人工腐蚀环境下,进行了一组加载频率为0.1 Hz的不同位移条件下不锈钢波形膨胀节腐蚀疲劳寿命试验。通过回顾国内外常用的膨胀节疲劳设计公式,在EJMA标准疲劳设计公式基础上提出了腐蚀加速效应系数Ccorr,从试验数据拟合出Ccorr的大小,据此提出了腐蚀条件下膨胀节疲劳设计公式,用于修正腐蚀条件下膨胀节的疲劳寿命。     

1Cr18Ni9Ti与16MnR异种钢埋弧自动焊研究与应用

1Cr18Ni9Ti与16MnR是超高压开关壳体常用钢板,通过对1Cr18Ni9Ti不锈钢与16MnR低合金钢埋弧自动焊单面焊双面成型工艺的研究,分析了1Cr18Ni9Ti与16MnR异种钢焊接容易产生焊接缺陷的原因,通过大量工艺试验、评定,以此确定出1Cr18Ni9Ti与16MnR异种钢埋弧自动焊单面焊双面成型合理的焊接工艺,并在生产实际中得到了应用。     

汽轮机低压转子2Cr13不锈钢叶片断裂分析

通过断口宏观形态分析、扫描电镜(SEM)微观观察、能谱(EDS)分析和显微组织分析以及常规力学性能测试,对电站汽轮机低压转子2Cr13不锈钢叶片断裂失效模式和失效原因进行了全面的分析,并对开裂机制进行了深入探讨.结果表明:该汽轮机低压转子2Cr13不锈钢叶片的失效模式为腐蚀疲劳破坏,叶片材质较差的内部因素和腐蚀疲劳的工况条件共同作用造成了叶片的断裂失效.     

Characterisation of joint properties through spatial mapping of cracks in fatigue specimens,extracted from the linearly friction welded steel coupon

Linear friction welding (LFW) is widely used for the fabrication of high-value components in the aero-industry. The versatility of use and high integrity of joints produced by LFW, suggest that this technology could contribute greatly to sustainable engineering of the future. For example, in near-net-shape manufacturing, LFW is predicted to offer a substantial reduction in material waste and processing time, in addition to offering the capability of bonding material pairs currently difficult to fusion weld. LFW of steel components is seldom researched in published literature, with little information available on fatigue strength and fracture behaviour of such joints. This may hamper the confidence needed to popularise LFW in wider industry. Thusly, authors conducted a discovery-oriented fatigue study, followed by metallography and micro-hardness tests, conducted on a 100Cr steel LFW coupon and corresponding batch of parent material. The weld coupon was dissected into a set of fatigue specimens, to allow mapping of the joint's internal properties through individual fatigue estimates and fracture morphology of each specimen in the set. A prototype fatigue machine was constructed, designed to deliver independent displacement and force controlled bending or torsional loadings, representing complex real-world conditions more accurately than common, uniaxial tests. The hour-glass shape of fatigue specimens allowed for targeting strictly the weld region, inducing fracture at the weakest material section, which was found to lay far outside the immediate contact interface. Referencing distances from fracture points to the theoretical weld interface plane in each fatigue trial, resulted in discovery of a macroscopic pattern. Interpolated to a crack initiation plane, this pattern is proposed to reflect the heat-affected zone, across the greater LFW coupon. Authors also studied crack paths and suggest a link between fracture direction, residual stresses in joint and angular orientation of the crack initiation plane in respect to the theoretical weld interface.     

预测腐蚀疲劳寿命的概率方法

在建立航空发动机铝合金构件点状腐蚀和腐蚀疲劳裂纹扩展模型的基础上，将铝合金叶片的机械腐蚀特性和由环境诱导的电化学行为看作是随机量或随机过程，提出腐蚀疲劳寿命预测的概率方法，利用重要随机变量的累积分布函数，估算寿命累积分布函数，预测腐蚀疲劳寿命。     

一种基于参数影响的数据驱动下的疲劳寿命预测方法

金属构件的主要失效方式是在循环载荷作用下的疲劳破坏,因此金属构件的疲劳寿命预测对于保证结构安全性和可靠性十分必要。能量法是一种既能用于低周疲劳寿命预测,也能用于高周疲劳寿命预测的方法,其以寻找有效的显式能量损伤参量为手段,结合适当的损伤积累方式进行寿命评估。针对材料疲劳寿命预测问题,提出一个基于能量法和人工神经网络算法的疲劳寿命预测方法。为了达到反映不同加载路径影响的目的,从转动惯量的角度引入两个路径相关参量。使用基于应变控制的九种材料的疲劳试验数据对提出的神经网络模型进行训练、测试。结果显示模型对训练数据和测试数据均有良好的预测精度,并可对单轴加载、多轴加载、高周疲劳和低周疲劳寿命进行有效预测,表明本模型在多轴疲劳寿命预测方面具有较广泛的适用性。     

调质45钢变幅载荷下疲劳寿命预测

通过调质 45钢的超载实验及变幅疲劳实验 ,进一步验证作者提出的变幅载荷下疲劳寿命及其概率分布预测方法的适用性。实验结果及分析结果表明 ,调质 45钢切口件的超载效应因子 Z=0 ,从而可不必考虑载荷顺序效应 ,而直接采用 Miner法则和恒幅下的疲劳寿命曲线表达式进行预测 ,且实验结果与预测结果吻合很好     

钢丝微动疲劳裂纹萌生寿命预测研究*

钢丝微动疲劳过程中,钢丝裂纹萌生特性直接影响其裂纹扩展特性,进而制约钢丝微动疲劳寿命,因此开展钢丝微动疲劳裂纹萌生寿命预测研究具有重要意义。基于有限元法、摩擦学理论和断裂力学理论,运用Smith-Watson-Topper（SWT）多轴疲劳寿命准则建立考虑磨损的钢丝微动疲劳裂纹萌生寿命预测模型,基于多种不同的钢丝疲劳参数估算方法对钢丝的微动疲劳裂纹萌生寿命进行了预测,并探究接触载荷、疲劳载荷、交叉角度及钢丝直径等微动疲劳参数对钢丝微动疲劳裂纹萌生寿命的影响规律。结果表明：基于中值法的预测结果最接近实际值;在微动疲劳过程中,钢丝微动疲劳裂纹萌生寿命主要与接触载荷和疲劳载荷相关。通过引入微动损伤参数建立简化的适用于钢丝绳的钢丝微动疲劳裂纹萌生寿命预测模型,通过与考虑磨损的预测模型计算结果进行对比验证了该模型的准确性。     

Fretting fatigue of single crystal nickel at 600 °C

An experimental setup has been developed to conduct fretting fatigue tests at 610 °C and fretting fatigue lives are characterized for the contacting pair of IN100 and single crystal nickel subjected to a range of loading conditions. A well characterized set of experiments have been conducted to obtain the friction coefficient in the slip zone. A robust quasi-analytical approach, based on solution to singular integral equations, has been used to analyze the contact stresses. Different multi-axial fatigue parameters have been investigated for their ability to predict the initiation life of the specimens. An estimation of crack propagation life was made using conventional fracture mechanics approaches, after making certain assumptions to simplify the problem. Total life was predicted using nucleation life from different parameters and propagation life from conventional fracture mechanics approach. These predicted lives were compared with experimentally observed failure lives. The quality of the comparison provides confidence in the notion that conventional life prediction tools can be used to assess fretting fatigue at elevated temperatures.     

电镀铜薄膜疲劳性能与寿命预测

利用MMT-11N微机械疲劳试验系统对11.5 μm厚无基体支持的电镀铜薄膜试件的拉伸疲劳特性进行了试验研究。试件采用准LIGA工艺制作。试验在室温条件下进行,采用载荷控制、脉动循环加载,载荷频率为20 Hz,得到了铜薄膜光滑试件和缺口试件的S-N曲线,根据传统宏观疲劳理论确定了铜薄膜循环应力—应变曲线和应变—寿命曲线。利用修正局部应力—应变法对缺口试件的疲劳寿命进行了预测,预测寿命与试验寿命误差在3.2倍因子之内,预测结果较好地符合试验结果。试验表明,取半寿命周期的迟滞回线作为稳定迟滞回线在微机械疲劳中仍是可信的,局部应力—应变法亦可应用于微机电系统疲劳寿命预测,宏观疲劳理论在一定程度上也适合于描述微机械疲劳。     

非比例载荷下304不锈钢低周疲劳寿命预测

在拉扭疲劳试验机上完成了一系列非比例加载下对304不锈钢的低周疲劳试验,对目前常用的几种多轴疲劳寿命预测模型进行了分析比较。结果表明,以单轴疲劳寿命分析方法为基础的等效应变法,不能预测多轴非比例加载下的低周疲劳寿命,以临界面法为基础的Socie剪切模型对非比例加载下304不锈钢材料的疲劳寿命预测较好。