252kV GIS机构止动螺栓的断裂失效分析

某批次35Cr Mo合金钢252 k V气体绝缘金属封闭开关设备(GIS)机构电镀锌止动螺栓在合闸试验调节中发生断裂失效,通过化学成分分析、断口分析、硬度测试、氢脆评估试验、金相检验等方法对螺栓断裂原因进行了分析。结果表明:该止动螺栓断裂是由氢脆造成的,而止动螺栓发生氢脆断裂是由螺栓电镀锌后去氢工艺不当造成的。最后提出了预防螺栓氢脆断裂的改进措施。     

高压燃油泵溢油阀断裂失效分析

某高压燃油泵溢油阀在服役过程中发生断裂,通过尺寸设计与原材料选用分析、化学成分分析、断口分析、金相分析、有效硬化层深度测试、硬度测试、镀锌层厚度测试、孔径尺寸测试等方法对溢油阀断裂原因进行了分析。结果表明:该溢油阀失效模式属于氢脆延迟断裂。溢油阀表面渗碳淬火处理导致其硬度偏高,氢脆敏感性增强;酸洗镀锌过程中由于未进行脱氢处理,导致溢油阀表面发生氢聚集,最终在安装应力和氢的共同作用下发生氢脆断裂。最后针对溢油阀断裂原因提出了预防措施。     

65Mn弹簧卡断裂失效分析

采用断口分析、金相检查、能谱分析和氢含量检测等方法,对65Mn弹簧卡在使用过程中发生的断裂原因进行了分析判断。结果表明：弹簧卡失效断裂原因为镀锌处理造成了较大氢致内应力以及晶界被弱化而引起的氢脆断裂。     

两种零件不同条件下氢脆断裂分析

对两种零件不同条件下氢脆断裂的宏、微观形貌特征进行了观察与分析,并对断裂构件的氢含量进行了分析测试.结果表明,钢制构件中氢含量超过一定值后均可发生氢脆断裂.构件是否发生氢脆断裂以及氢脆断裂的宏、微观形貌特征与构件中的氢含量、材料强度、所受应力状态等有关.     

某导弹位标器用弹簧垫圈失效分析

某型号导弹住标器用弹簧垫圈在现场装配时发生断裂,对断裂件进行了化学成分、硬度和宏、微观检验。结果表明．弹簧垫圈冶金质量符合要求;其断裂失效是镀锌后除氢不彻底．导致装配时发生氢脆断裂。提出了建议。     

双头螺栓失效分析

与汽车电机装配在一起的双头螺栓在拧紧后不久便发生断裂。采用扫描电镜、化学分析、金相检验等方法对失效件进行了检测，同时又进行了氢脆试验验证。结果表明，螺栓在进行表面酸洗及电镀时，氢向金属内部扩散和富集，当氢浓度达到一定临界值后，促使氢致裂纹的产生和扩展。在外应力的作用下，即出现氢脆现象导致螺栓断裂。     

发动机缸盖螺栓断裂原因分析

某发动机缸盖螺栓在装配后发生断裂。通过宏观、微观检验以及化学成分分析、力学性能测试、氢脆试验等对断裂原因进行了分析。结果表明:缸盖螺栓发生了氢脆断裂。其原因是缸盖螺栓在表面磷化后的去氢处理不当,导致装配后缸盖螺栓在拉应力的作用下产生氢脆裂纹,并最终发生断裂。     

镀锌螺栓的断裂分析

镀锌螺栓在组装后放置1～2d于根部或头部发生大量断裂,采用化学成分分析、金相检验、硬度检测及断口分析等方法对螺栓的断裂性质及断裂原因进行了分析。结果表明：螺栓断裂为典型的氢脆断裂;主要原因是螺栓在后期酸洗和电镀过程中除氢不彻底,吸入了大量的氢;次要原因是热处理工艺控制不当,使螺栓心度硬度偏高,增加了其对氢脆的敏感性;两者共同作用最终导致螺栓发生氢脆断裂。     

70钢拉簧氢脆断裂失效分析

对７０钢拉簧在制造及使用过程中出现的失效断裂特征做了分析，结果表明，拉簧断裂是电镀过程吸氢导弹的氢脆断裂，对此，提出了改进措施。     

十字槽沉头螺钉断裂失效分析

材料为ML30CrMnSiA钢的十字槽沉头螺钉在初次装配过程中发生批量断裂失效,通过宏观观察、化学成分分析、力学性能试验、金相分析、断口扫描电镜及能谱分析、氢含量测定等方法对螺钉断裂原因进行了分析。结果表明:螺钉头部的十字槽底部在冷镦或热处理过程中产生微裂纹,在酸洗、镀镉等工序中,氢沿微裂纹渗入基体,加之螺钉强度偏高,超过设计要求,从而导致螺钉发生氢脆开裂并扩展,实际承载面积降低,最终在装配应力作用下发生断裂失效。     

辊套断裂原因分析

本文采用化学分析、力学性能、金相组织、断口分析等方法研究了辊套的断裂行为。结果表明,辊套断裂是由于氢脆造成,辊套失效与材料缺陷及热处理工艺不良有关。     

Hydrogen Embrittlement on High-Speed Stainless Steel Belts Used for Tin Plating Chip Lead Frame

The 300 series stainless steels generally exhibit good corrosion resistance in common use. However, a premature fracture event caused by hydrogen embrittlement was encountered on 300 series stainless steels which was used as belt hanging chips in a tin plating process for the chip lead frame. The cause of the fracture was carefully studied. A metallurgical microscope and photoelectric direct reading spectrometer were used to examine the metallographic structures and chemical compositions of the matrix material. A scanning electron microscope and energy disperse spectroscope were also applied to analyze the micro morphologies and micro-area composition of the fracture. Meanwhile, the chemistry and hydrogen content of the process media were inspected by ion chromatography and hydrogen analyzer. In addition, the finite element method was employed to simulate the effect on the belt from the service conditions. The analysis results revealed that the unqualified material selection, the aggressive media, and the inappropriate technological parameters were the main causes of the failure. Furthermore, the mechanisms of hydrogen embrittlement were discussed, and countermeasures and suggestions were put forward.     

电镀氢脆故障及应对措施

电镀过程中作为阴极的被镀零件在获得镀层的同时在零件金属内部也渗入了氢,如果该零件金属对氢脆敏感、又有拉应力存在时便可能发生氢脆,使零件断裂,甚至诱发事故.介绍了几例典型的氢脆故障,结合实例分析指出,渗入金属内部的氢是可逆氢,可以通过加热烘烤排出,以避免事故发生.     

Failures of engineering components due to environmentally assisted cracking

Examples of failures of engineering components by stress-corrosion cracking, corrosion-fatigue, hydrogen embrittlement, liquid-metal embrittlement, and solid-metal embrittlement are described. Causes of failure include inappropriate materials selection or heat treatment, poor design, and high residual stresses. The examples illustrate how fractographic characteristics, analysis of films and deposits on fracture surfaces, and other factors help in diagnosing the modes and causes of failures, thereby enabling the appropriate remedial measures to be taken.     

Hydrogen Embrittlement Failure of a Galvanized Washer

A galvanized washer used for a locomotive impeller broke into three pieces after an accumulative service of 4–5 h. The washer is fabricated from 42CrMo steel and the fracture surfaces reveal intergranular fracture morphology with microvoid coalescence observed on the facets. Microstructure observation indicates the presence of a severely banded microstructure mainly consisting of untempered martensite and bainite. The average hardness of the failed washer is HRC 59.1. The hardness value is much higher than specified (HBW 260-300) and is in the range of hydrogen embrittlement susceptibility. The significant number of elongated MnS inclusions acting as traps of hydrogen are present in the martensite regions. The delayed fracture associated with the predominance of intergranular fracture micromechanism and the high hardness level and the presence of microstructure susceptible for the hydrogen embrittlement strongly suggest the hydrogen embrittlement being the mostly possible failure mechanism. The likely sources for hydrogen entrapment are the electro-galvanizing process and acid-pickling before galvanizing. The hydrogen was retained in the washer due to absence of baking treatment to remove it or insufficient baking. The incorrect heat treatment process before galvanizing resulting in the high hardness level of the washer is mainly responsible for the occurrence of hydrogen embrittlement on the washer.     

汽车方向盘自挤螺钉断裂分析

采用断口分析、金相检验、显微硬度测试、化学成分分析、氢脆预载荷试验等方法对某型号乘用车方向盘固定螺钉的断裂原因进行了分析。结果表明：螺钉的断裂性质是氢致延迟断裂,裂纹起源于螺钉头下第一牙底。电镀后驱氢不充分致使螺钉表层残留较高含量的氢,表面渗碳层及首牙处的应力集中构成了导致氢脆的3个敏感因素。     

Failure in a high pressure feeding line of an oil refinery due to hydrogen effect

This work describes failure analysis of a feeding pipeline of an oil refinery. For this analysis visual inspection, dye penetration, optical and electron microscopy, XRD, tensile tests, fracture toughness tests and stress calculations were used. Result of the investigations show that hydrogen embrittlement has played an important role in the failure of the pipeline. For completing the case, hydrogen embrittlement damage of the piping material made from commercial ASTM A105M low alloy manganese steel was studied by using baking and hydrogenation treatments. Baking treatment was carried out at 520 °C for 20 min followed by slow cooling while hydrogenation treatment was carried out in a solution of H₂SO₄ which contained As₂O₃ for 0–6 h under cathodic situation. Then change in the mechanical properties and fracture toughness of the steel after the treatments were measured by tensile and fracture toughness tests. In addition, fractography was carried out using a scanning electron microscope (SEM) and image analyzer. Results show that the baking treatment increased elongation to failure and fracture toughness significantly and reduced yield strength slightly compared to the failed condition of the pipe. Hydrogenation treatment decreased elongation to failure and fracture toughness of the material considerably and increased strength barely. Increase in the hydrogenation time reduced ductility of the steel further more. These results indicate that hydrogen through hydrogen embrittlement mechanism, made the pipe material brittle and susceptible to cracking. Embrittlement with the assistance of an emergency shutdown and stress concentration provides damage nucleation and finally developed brittle fracture.     

Failure analysis of a river water circulating pump shaft from a NPP

This paper presents the failure analysis of a river water circulating pump from a Nuclear Power Plant. The failed component was the upper shaft made of martensitic stainless steel. The metallurgical analyses performed include fractography, metallography and energy dispersive spectrometry analysis. Charpy impact, tensile and hardness tests were also performed. The destructive examination carried out revealed that the root cause of the pump shaft failure was an improper thermal treatment of the material that generated a temper embrittlement process. However, in addition, a hydrogen embrittlement process could have contributed to the failure.     

Finite Element Analysis of Hydrogen Transport in Steel Pressure Vessel at Room Temperature

Hydrogen embrittlement is commonly considered as an important failure mechanism for steel pressure vessels and pipes made of such as Cr–Mo and 4130X steels under high-pressure hydrogen environments, which means hydrogen atom can easily penetrate and diffuse into the metal, leading to the distortion of microscopic lattice and the degradation of macroscopic strength and fracture toughness. Under the support of the National Key Fundamental Research and Development Project of China (2015.1-2019.12), we aim to launch a series of theoretical, experimental, and numerical research on the macroscopic damage evolution and microscopic fracture of steel structures under high-pressure hydrogen environment, which ultimately commits to gaining deep insight into the hydrogen embrittlement mechanisms. This work studies the hydrogen transport mechanisms in Cr–Mo steel pressure vessels under different hydrogen environments using finite element analysis (FEA), which is fundamental to subsequent research on the hydrogen-induced damage evolution and crack behaviors. The purpose of this paper is to explore the effects of the initial hydrogen concentrations and structural sizes on the hydrogen transport mechanisms in 2.25Cr-1Mo pressure vessels with a nozzle at room temperature. Numerical results by comparing different hydrogen concentration distributions show that structural discontinuities tend to accelerate the hydrogen embrittlement sensitivity.