汽轮机低压转子1Cr12Ni3Mo2VN不锈钢叶片的开裂原因分析

对某火力发电厂2号汽轮机组末级开裂叶片进行宏观检查、化学成分分析、金相组织以及断口扫描和元素成分能谱分析。结果表明：该叶片裂纹形成属于腐蚀疲劳失效,蒸汽中存在氯、硫等腐蚀介质引起叶片发生电化学腐蚀,在离心拉应力作用下发生沿晶应力腐蚀开裂,形成裂纹源。在腐蚀介质、拉应力和激振力综合作用下,腐蚀疲劳裂纹加速扩展,并最终发生瞬时断裂。     

滑油管裂纹分析

采用显微组织、断口分析及微区成分分析等手段,对滑油管裂纹进行了分析.结果表明,在长期停放过程中,滑油管内壁由于氯离子作用产生局部腐蚀.在装机使用后,由于振动应力的作用,产生了早期疲劳裂纹.滑油管裂纹系装机使用前管内壁腐蚀损伤引起的疲劳裂纹.     

发动机三级涡轮叶片断裂分析

某发动机三级涡轮转子叶片在飞机赶快冰爬升时断裂，通过断口ＳＥＭ观察，ＥＤＡＸ成分分析，叶片基材金相检验和硬度测试等分析了叶片的断裂原因和机制，结果表明，共振是叶片失稳断裂的直接原因，热疲劳萌生裂纹，高温腐蚀疲劳控制裂纹稳态扩展，材料冶金缺陷对叶片断裂过程有促进作用。     

某电厂600MW机组叶片断裂分析

某电厂600 MW超超临界机组在检修中发现一只低压叶片断裂,采用宏观分析、金相检验以及断口分析等方法对叶片断裂原因进行了分析。结果表明:叶片服役环境中存在能够引起叶片材料产生腐蚀的氯离子,导致叶片发生腐蚀疲劳断裂。     

叶片多源疲劳断裂分析

用金相，电镜，能谱仪等手段对叶片多源疲劳断裂进行了分析，结果表明，Ｃｒ的分布不匀易萌生疲劳裂纹，从而导致叶片的腐蚀疲劳断裂，提出了改进措施。     

柴油机进气门断裂原因分析

电镜分析结果表明,进气门断裂为多源腐蚀疲劳断裂.断裂原因是固溶处理效果不佳,抗腐蚀性能较低,在工作环境介质中,表面产生腐蚀坑和裂纹,裂纹扩展以致断裂.     

某发动机压气机三级转子叶片断裂原因

某发动机压气机三级转子叶片发生断裂,采用宏观观察、化学成分分析、扫描电镜和能谱分析、金相检验、硬度测试等方法,并结合叶片振动模态分析,对其断裂原因进行分析。结果表明：叶片的断裂性质为疲劳断裂,疲劳起源于叶片叶盆面距离进气边约0.8 mm的腐蚀坑处;腐蚀坑降低了叶片的抗疲劳能力,是叶片发生疲劳断裂的主要原因;叶片在工作转速范围内存在11阶共振,引起叶片疲劳裂纹的萌生和扩展。     

注水阀弹簧断裂原因分析

注水阀弹簧在使用约6个月发生断裂。采用宏、微观检验和化学成分分析等方法对失效件进行了检测。结果表明,该弹簧断裂为腐蚀疲劳断裂。疲劳裂纹的形成是由于消毒氯水在弹簧应力最大的第一与第二圈并圈处产生许多蚀坑,材料中非金属夹杂物加速了腐蚀向基体内延伸,为弹簧的疲劳断裂提供了裂纹源,在工作应力的作用下导致弹簧断裂失效。     

某电厂汽轮机叶片断裂失效分析

某电厂汽轮机在检修过程中发现多处叶片断裂,采用宏观分析、金相检验、断口微观分析和能谱分析等方法对汽轮机叶片的断裂原因进行了分析。结果表明:蒸汽和Cl-,S2-,Na+等与汽轮机叶片发生反应,在叶片上产生局部点腐蚀,形成腐蚀疲劳源;同时因叶片上存在离心力和蒸汽压力等复杂的周期性交变应力,最终造成汽轮机叶片发生腐蚀疲劳断裂。     

超声深滚处理改善预腐蚀7A52-CZ铝合金疲劳性能机理

研究了超声深滚(UDR)处理对预腐蚀7A52-CZ铝合金疲劳性能的作用.7A52铝合金试样在剥蚀腐蚀溶液中浸泡不同时间后进行了超声深滚处理.分别对未腐蚀试样、腐蚀试样和腐蚀+UDR处理试样进行了疲劳试验,用XRD应力测试和扫描电镜等方法分析了UDR处理前后试样的残余应力和断口形貌,并对疲劳断口进行了分析.结果表明:UDR处理在铝合金中引入超过1mm深的残余压应力层,延长了7A52的预腐蚀疲劳寿命.对于腐蚀较轻的试样,UDR处理使裂纹源在表层下残余压应力和拉应力过渡区产生,延长了疲劳裂纹萌生寿命;对腐蚀较重试样,疲劳裂纹仍从晶间腐蚀处形核,但由于引入残余压应力及腐蚀裂纹的部分愈合效应,仍在很大程度上改善了7A52的预腐蚀疲劳寿命.     

高速离心泵叶片断裂分析

对高速离心泵断裂叶片的材料成分,断口和力学性能进行了分析,确定了其断裂模式为腐蚀疲劳断裂,叶片根部加工粗糙,造成局部应力集中是导致叶片断裂的主要原因,对叶片的结构设计进行了探讨。     

汽轮机叶片断裂分析

实际服役寿命为5年的汽轮机叶片发生了断裂.对叶片断口、材料的化学成分、显微组织和力学性能进行了分析.结果表明,叶片的断裂属于高周低应力疲劳断裂.针对叶片失效情况提出了一些相应的预防措施.     

Failure of aircraft propeller assembly

This paper analyses the causes of the incident of a Cessna trainer whose propeller was separated due to the cracking of the propeller blade hub during the take off roll. Beach marks and fatigue striations, typical of fatigue cracks, were observed on the fracture surface and corrosive oxides were detected in the center of beach marks that are considered to be the crack origin. The stress acting on the fracture surface under a corrosive environment forms corrosive oxides, such as mud cracks. By analyzing the fractography and metallography of the failed parts, it is found that the propeller blade hub nucleated stress corrosion cracking (SCC) as a result of residual stress and corrosive environment and the SCC was the cause of the fatigue crack. Moreover, a fatigue crack reaches its critical length by repeated cyclic stress, which occurs during the rotation of the propeller blade and then, the rest of the fracture occurred instantaneously.     

Failure analysis of a second stage blade in a gas turbine engine

The failure of a second stage blade in a gas turbine was investigated by metallurgical and mechanical examinations of the failed blade. The blade was made of a nickel-base alloy Inconel 738LC. The turbine engine has been in service for about 73,500 h before the blade failure at 5:50 PM on 14 August 2004. Due to the blade failure, the turbine engine was damaged severely. The investigation was started with a thorough visual inspection of the turbine and the blades surfaces, followed by the fractography of the fracture surfaces, microstructural investigations, chemical analysis and hardness measurement.

The observation showed that a serious pitting was occurred on the blade surfaces and there were evidences of fatigue marks in the fracture surface. The microstructural changes were not critical. It was found that the crack initiated by the hot corrosion from the leading edge and propagated by fatigue and finally, as a result of the reduction in cross-section area, fracture was completed.

An analytical calculation parallel to the finite element method was utilized to determine the static stresses due to huge centrifugal force. The dynamic characteristics of the turbine blade were evaluated by the finite element modal and harmonic analyses. Finally according to the log sheet records and by using a Campbell diagram there was a good agreement between the failure signs and FEM results which showed the broken blade has been resonated by the third vibrational mode occasionally before the failure occurred.     

Evaluation of vibration-induced stresses in teeth of rotor disks of compressors of gas-turbine engines

We show that loads induced in turbine blades by vibration make a significant contribution to the dynamic stressed state of the teeth of compressor disks. The dynamic stresses formed in the teeth of the investigated blade wheels can be as high as 42% of the stresses induced in the blades. Together with fretting corrosion, static stresses, and other factors, this may lead to initiation and propagation of cracks in teeth and, as a final result, their fracture.     

Assessment of causes of fracture in 14Kh17N2 steel blades of GTK-25I gas-pumping unit axial-flow compressors

Causes of fracture of the martensitic-ferritic steel blades of the variable inlet guide vane for an axial-flow compressor of the gas pumping unit GTK-25I have been studied. There are several stages of blade fracture: corrosion, fatigue, and fracture. At the initial state, corrosion damage occurs at the martensite-ferrite interface, which is followed by intragranular corrosion damage along martensite needles and fatigue failure within the grain bodies. __________ Translated from Problemy Prochnosti, No. 5, pp. 129–133, September–October, 2008.     

烧结厂排烟风机失效分析

对烧结厂排烟机炸毁现场进行了调查,分析了风机失效原因,结果表明,叶片角焊缝根部存在多种焊接缺陷,致使其疲劳强度下降,在复杂应力作用下,促使裂纹萌生和扩展,造成叶片从叶轮上脱落并将其它叶片撞断,最终导致风机系统严重损坏。     

5号汽轮机叶片断裂原因分析

对某热电厂5号汽轮机的断裂叶片进行了宏观形貌、化学成分、金相组织以及扫描电镜形貌和元素成分能谱分析。结果表明,叶片失效性质为腐蚀疲劳断裂;叶片拉筋孔处的点蚀坑是裂纹源;造成叶片发生点蚀的原因是蒸汽中含有的氯、硫等介质。     

换热器紧固螺栓的应力腐蚀断裂分析

紧固螺栓服役2年后发生成批断裂.采用宏观观察、化学成分分析、金相检验和扫描电镜与能谱分析等方法对失效螺栓进行了分析.结果表明,由于紧固螺栓长期浸在含有H2S介质的油料中,并在所承受的各种应力下又与腐蚀环境相互作用便产生了应力腐蚀,加上螺栓材质选用不当和硬度、显微组织不合理等其他因素,最终导致螺栓断裂.