65Mn钢波形垫圈断裂分析

本文从化学成分、显微组织、断口形貌、氢含量、硬度等方面,对表面镀镉65Mn钢波形垫圈使用过程中连续出现早期断裂的原因进行了分析。对同批零件进行了氢脆和回火脆性验证试验,分析了除氢时间、氢含量、硬度以及回火温度对断口形貌的影响,同时对不同硬度检测方法对垫圈硬度值的影响进行了分析。结果表明,硬度浏量方法选择不当导致波形垫圈的实际硬度超出技术要求,使波形垫圈脆性增加,引起波形垫圈最终断裂,残余氢导致断口呈沿晶特征。建议将该波形垫圈回火温度控制在380-410℃范围内,选择HV5.0或HV10检测硬度,除氢时间不低于12h。     

鞍形弹性垫圈断裂原因分析

通过对断裂铍青铜鞍形弹性垫圈断口进行宏观微观观察、金相组织检查、硬度测试等理化分析,以及对同批次原材料进行组织检验分析断裂原因。结果表明:断裂垫圈断口呈沿晶韧性断裂特征,主要是硬度偏技术要求上限,增加了材料的脆性引起断裂,并提出了相应改进措施。     

阴极极化对高强度船体结构钢焊缝氢脆敏感性的影响

在恒定阴极电位下利用慢应变速率拉伸试验研究高强度船体结构钢焊缝的电化学性能和力学性能。结果表明,试样拉伸断裂主要发生在焊缝的熔合区;结构钢的阴极极化程度对抗拉强度和屈服强度的影响不大;随阴极电位负移,船体结构钢在海水中的延伸率、断裂时间和断裂应变率逐渐减小, 并且当施加阴极电位为-0.89 V（vs SCE）时各项性能最佳。同时,随着阴极电位负移,断裂方式逐渐从韧性断裂向脆性断裂发展,氢脆敏感性逐渐增加,在 -0.70 V~-0.89 V（vs SCE）之间氢脆敏系数低于5%,不发生氢脆;当电位负于-0.94 V（vs SCE）,氢脆敏感性迅速提高,当极化电位为-0.99 V （vs SCE）时氢脆系数显著增大至20%,断口开始出现解理单元细小准解理断裂特征;在负于-1.04 V（vs SCE）时,氢脆系数已高于25%,进入危险区,且断口开始出现较多解理单元粗大的准解理、解理等氢脆断裂特征;随着电位继续负移至-1.14 V（vs SCE）,断口完全出现解理组织、沿晶、穿晶结构或者两者混合的氢脆断裂特征。     

组合开关紧固用弹性卡箍失效分析

针对三菱汽车某款组合开关模块紧固用弹性卡箍的断裂失效现象,对弹性卡箍零件进行应力分析,发现最大应力在减料孔端部。对失效零件进行化学成分、金相组织、断口形貌分析,得出零件断裂主要为"氢脆断裂"。在此基础上,提出通过震动时效来消减应力和采用久美特表面涂层处理代替表面电镀锌处理来杜绝"氢脆"的方法。实验和装车运行证明了此解决方案的有效性。     

汽车缸盖螺栓断裂原因分析

汽车发动机用的一批35CrMo钢缸盖螺栓使用不久后即发生大比例的断裂,断裂位置都位于螺纹尾部磨削加工段,且断口形貌都比较接近。化学成分、显微组织、硬度、表面和断口形貌的检查和分析结果表明,断裂螺栓属于氢脆引起的延迟断裂。断裂批次螺栓的酸洗工序安排在了磨削和滚丝之后,螺纹尾部在酸洗后即出现了大量表面沿晶微裂纹,服役过程中沿晶裂纹进一步扩展并最终断裂。存在过酸洗和酸洗工序安排不合理是引起螺栓断裂的主要原因。     

三角杆自攻螺栓断裂分析

三角杆自攻螺栓装配后延时断裂,通过断口分析、金相检查、硬度测试以及氢含量测定,对其断裂原因进行了分析。发现螺栓断裂原因是氢脆,据此提出了消除氢脆的方法和改进措施。     

40吨起重机后桥齿轮早期失效原因分析

本文通过对早期失效后前桥主齿轮截面抛光,断口宏观,光学显微,电镜观察分析结果表明,齿表层达32μm深的黑色网状物,碎片呈辉光疲劳剥落,脆断,裂源起始于表层不完全淬火组织并沿着黑色网而扩展,断口为密集冰糖状化合物,具有氢脆爪状撕裂线及沿晶断裂的典型特征。     

电力机车连接螺栓断裂分析

采用宏观观察、金相检验、成分分析、力学性能检测及断口分析对断裂的连接螺栓进行分析。结果表明:螺栓呈现脆性断裂特征,裂纹源位于螺杆与六角头过渡处,源区微观特征为沿晶+准解理,晶面上存在孔洞及撕裂棱,具有氢脆断裂的特征,并且在螺杆与六角头过渡处存在过度腐蚀的特征;螺栓断裂的主要原因为酸洗过度导致过多的H渗入基体内,在扭转应力和拉伸应力共同作用下,发生氢致延迟断裂。     

碳氮共渗处理时氢脆问题的探讨

通过电镜断口分析、氢含量对比等方法对驱动轴的断裂原因进行了分析。结果表明:驱动轴断裂为氢脆断裂。产生氢脆的原因是零件在碳氮共渗时存在渗氢现象;主要渗碳介质中水分含量超标是导致氢脆的主要原因。并提出了改进方法,取得了良好效果。     

飞机盖板螺栓断裂失效分析

某飞机服役一段时间后，机翼盖板1根螺栓发生断裂。通过外观痕迹和断口形貌观察、显微组织检查、硬度测试、能谱成分分析、氢含量测试以及氢脆试验，对螺栓的断裂性质和原因进行了分析。结果表明，螺栓断裂性质为氢致延迟脆性断裂。材料强度偏高，氢脆敏感性较大是螺栓发生氢脆断裂的内因，表面局部腐蚀吸氢是导致螺栓氢脆断裂的直接原因。调整热处理工艺，在满足设计要求的前提下适当降低螺栓的强度，同时加强螺栓的腐蚀防护，可以有效预防氢脆断裂的发生。     

电化学充氢对Cr15铁素体不锈钢和304奥氏体不锈钢氢脆敏感性的影响

研究了充氢时间、充氢电流密度、晶体结构对不锈钢氢脆敏感性的影响。结果表明:对于铁素体不锈钢,随着充氢时间的延长、电流密度的增大,塑性显著降低,氢脆敏感性大幅度增加;通过SEM观察实验钢断口形貌,断裂类型由韧性断裂转变为脆性断裂。而相同条件下,奥氏体不锈钢氢脆敏感性较低,抗氢脆性能较好。充氢后实验钢表面存在大量H,且氢含量随试样深度逐渐降低,晶界可能作为氢陷阱影响实验钢的氢脆敏感性。     

飞机起落架固定螺栓氢脆断裂研究

飞机起落架一固定螺栓发现裂纹,经断口宏观观察、微观观察、金相检查、硬度检测及H含量测定,综合分析确定该型螺栓的断裂性质,并分析断裂失效的原因。研究结果表明,螺栓的断裂性质为氢脆断裂,其修理过程中发生塑性变形产生局部应力集中,电镀前未除应力是氢脆断裂诱因,并导致最终断裂。建议该型螺栓修理时应严控表面处理过程,严格执行除应力措施,从而降低该型螺栓发生氢脆断裂的可能性。     

50CrVA弹簧断裂原因分析

50CrVA弹簧装配一段时间后发现断裂,后更换不同批次弹簧又发生断裂。对断裂弹簧进行断裂特征、组织观察分析,对硬度和镀层厚度进行测试。结果表明:存在表面镀层偏厚;弹簧的断裂性质为氢脆断裂;调查分析发现,断裂弹簧使用的表面处理槽液发生了改变,而工艺并未随之变化,致使在电镀过程中H的作用对弹簧影响较大,这是弹簧氢脆断裂的主要原因;此外,弹簧装配使用时不同轴导致应力集中,也对氢脆的发生有促进作用。工艺试验后,提出相应的改进措施,弹簧未发生断裂故障。     

Hydrogen-enhanced lattice defect formation and hydrogen embrittlement of cyclically prestressed tempered martensitic steel

The numbers of lattice defects formed by applying cyclic prestress with/without hydrogen for various numbers of cycles and strain rates during cyclic prestress were compared for tempered martensitic steel. A tensile test was also carried out to evaluate hydrogen embrittlement susceptibility following the application of cyclic prestress. The results showed that when cyclic prestress was applied without hydrogen, the number of cycles and strain rate had no apparent effect on mechanical properties and fracture morphology at the time of the subsequent tensile test. In contrast, when cyclic prestress was applied with hydrogen, the fracture strain and fracture stress decreased with an increasing number of prestress cycles and a decreasing strain rate, and the fracture morphology exhibited brittle fracture, signifying an increase in hydrogen embrittlement susceptibility at the time of the tensile test. The number of hydrogen-enhanced lattice defects also increased with increasing number of cycles and a decreasing strain rate was found when cyclic prestress was applied with hydrogen. These results indicate a correlation between hydrogen embrittlement susceptibility and the number of hydrogen-enhanced lattice defects. The kinds of increased hydrogen-enhanced lattice defects were probably vacancies and vacancy clusters formed by the interactions between hydrogen and dislocation movement during the application of cyclic prestress. The vacancies and vacancy clusters formed during the application of cyclic prestress with hydrogen presumably caused intergranular fracture and increased hydrogen embrittlement susceptibility.     

钢的氢脆的新研究方向

简要回顾了人们对钢的氢脆问题的认识过程和研究历史,概述了钢中氢的存在状态与氢脆的关系,钢的塑性变形与氢脆的关系,其中包括断口形貌和断裂过程。此外还论述了奥氏体不锈钢的氢脆及氢引起的断裂现象等共性问题。     

Effect of Hydrogen and Magnetic Field on the Mechanical Behavior of High Strength AISI 4340 Steel

Presence of hydrogen in materials is known to affect their mechanical properties due to hydrogen embrittlement problem. Steels used in various applications are prone to be exposed to aqueous electrochemical environments, which may introduce hydrogen into the alloy. These alloys are also prone to be simultaneously exposed to magnetic field, which may affect the hydrogen embrittlement susceptibility of these alloys. Therefore, it is important to examine the effect of hydrogen and magnetic field on the mechanical behavior of iron-based alloys. In this work, the effect of hydrogen and magnetic field on the fracture behavior of high strength AISI 4340 steel was examined. Three-point bend test was used to study the fracture behavior. In all the cases, the samples tested with hydrogen charging show a drastic reduction in ductility and fracture stress values. The effect of magnetic field was seen to be negligible. The hydrogen embrittlement was characterized by a change in the fracture surface from a ductile-type fracture to a brittle cleavage-type fracture. Acoustic emission signals collected during the test corresponds to the fracture behavior.     

Effect of hydrogen on the properties and fracture characteristics of TRIP 800 steels

The paper describes effect of hydrogen on the properties and fracture characteristics of two variants of TRIP 800 C–Mn–Si steels. The effect of hydrogen was studied by means of tensile tests on specimens previously charged by hydrogen. Hydrogen provoked embrittlement in both variants but only for very high hydrogen content. Hydrogen embrittlement manifested itself mainly by a loss of plasticity. Both steel variants were able to absorb a large amount of hydrogen, up to 50 ppm. Concerning fractographic characteristics, steels containing higher hydrogen content displayed transgranular cleavage fracture. In exceptional cases, an irreversible embrittlement was revealed initiating on non-metallic inclusions.     

30CrMnSiA合金前端吊耳断裂原因分析

某30CrMnSiA合金前端吊耳发生断裂,对断裂吊耳进行断裂特征分析和硬度测试。结果表明,吊耳断裂性质为氢脆断裂,且存在硬度超标现象。结合吊耳热处理和表面处理工艺对氢脆断裂原因进行分析,表面处理过程中除氢不彻底是造成氢脆的主要原因,而硬度超标不仅增加氢脆敏感性,且误导除氢工艺;同时该失效件反映了供应商质量控制上的不足,需在特殊过程及二次外包上加强控制和审核力度。     

On the intergranular fracture behavior of high-temperature plastic deformation of 1420 Al-Li alloy

Compared with generic industrial a1uminumalloys, Al-Li a1loys have remarkable advantagesinc1uding low density high specific strength,and rigidity. They are widely used in manyfields, such as aviation, spaceflight, energy en-gineering, weapon industry, etc. TherefOre,every country pays much attention to them.The l420 alloy belongs to Al--Mg--Li-Zr seriesalloys [ l, 2]. lt has excellent corrosion resistanceand good weldability besides the common ad-vantages of generic Al-Li alloys. lt can be…