某发动机二级涡轮叶片断裂失效分析

在叶片断口宏微观断裂特征观察的基础上,结合叶片的金相组织、力学性能、硬度以及化学成分等,对叶片断裂失效的原因进行了研究.结果表明,发动机二级涡轮叶片失效是由于其中一片涡轮叶片低周疲劳断裂所致.该叶片的低周疲劳断裂失效与源区附近的R槽中的微裂纹、Zr含量偏高、HRC偏高以及断裂处在高应力区等因素有关,且叶片经历了短时超温,其温度约在1050～1100℃之间.     

HK40钢的渗铝新工艺及抗碳化腐蚀性能研究

采用金相显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、X射线能谱分析仪(EDAX)等仪器设备研究了HK40钢的渗铝及其抗碳化腐蚀能力.试验结果表明,通过调整渗剂中特种添加剂与铝粉的比例和渗铝温度等工艺参数,可达到控制渗铝层相组成的目的.与传统一段法固体粉末渗铝工艺相比,两段法固体粉末渗铝工艺可提高渗速约60%.HK40钢的渗铝层由NiAl相和Ni3Al相组成时,其抗碳化腐蚀能力得到明显提高.     

燃气涡轮叶片的服役损伤与修复

涡轮叶片是燃气轮机最重要的热端部件之一。它长期在不均匀的温度场、应力场以及燃气腐蚀和高温氧化的环境下工作,面临着蠕变、低周疲劳和高温腐蚀等多种失效威胁。系统地研究涡轮叶片在服役过程中的组织损伤与性能退化规律是揭示其失效机理、探索适宜的恢复热处理工艺以延长涡轮叶片使用寿命的必然途径。对目前已有的涡轮叶片服役损伤研究进行了总结,同时结合本课题组对不同类型的涡轮叶片长期服役后（空中飞行时间：1 200 h~20 000 h）组织和性能损伤评估的研究结果,对存在的各种服役组织损伤形式进行了归类和介绍,主要包括涂层的退化、拓扑密排相（TCP）的析出、二次反应区（SRZ）的形成,γ′相的粗化与筏排化,碳化物的分解与析出,蠕变孔洞与裂纹的形成等。此外,还总结了前人研究的服役涡轮叶片性能退化规律以及恢复热处理工艺。热端部件服役损伤的研究对燃气轮机关键部件的寿命管理和安全服役具有重要的指导意义和经济意义。     

地面燃机涡轮叶片和导向叶片涂层的应用EI

介绍了国外燃用低质柴油的地面燃机一级涡轮叶片及导向叶片防护涂层的抗腐蚀性能 ,肯定了高 Cr- MCr Al X (M=Ni、 Co、 Ni Co,X=Y、 Si、 Hf)涂层防护效果。     

Non destructive investigation of the condition of Gas Turbine Blades

In order to determine the remaining life of service exposed turbine blades it is necessary to characterize the degeneration of the microstructure of the base metal during service. Since turbine blades of industrial gas turbines are kept in complete stages, non-destructive inspection (NDI) is very attractive. Hence the goal of the investigation reported here was to evaluate a NDI technique able to detect microstructural changes of the base metal. It was found that single-stage replication (in combination with investigation in a Scanning Electron Microscope) is a relatively simple technique that fulfils all requirements. This technique can be used in-situ on uncoated buckets. For coated turbine blades local removal of the coating is necessary to perform base metal replication.     

Failure Investigation of a Gas Turbine Inlet Weatherhood

Analytical and experimental methods have been used to investigate fatigue failures in the weatherhood protecting the air inlet to an offshore gas turbine power generation unit. A simple method for modelling transverse vibration of the leading edge is described, and the results are compared with experimental measurements made on a prototype installation. Calculation of the stresses induced at the critical locations, where cracking has been observed, suggests the failure should be attributed to aerodynamic excitation of the leading edge.     

Failure of Low-Pressure Turbine Blades in Military Turbofan Engines: Causes and Remedies

Failure of low-pressure (LP) turbine rotor blades in low bypass military turbofan engines is a great concern for designers, manufactures, repair and overhaul agencies, operators, and airworthiness authorities. The present paper analyzes the LP turbine blade failure cases to determine its root cause. Forensic and metallurgical investigations are carried out on the failed blades. In most cases, the failure was originated from the leading edge and had propagated toward the trailing edge. Intergranular features and high oxidation on the fractured surface have been found as the cause of fatigue failure. Operation at elevated temperatures for considerable time was found responsible for these fatigue failures. Malfunction of fuel system, failure in control sensors, and nonuniformity in atomizer characteristics were the root cause of high temperature in turbine leading to the failure of blades. The paper also presents various remedial measures to address the blade failures from manufacturing and operational points of view.     

Failure Prevention in Design Through Effective Catalogue Utilization of Historical Failure Events

The science of failure prevention relies heavily on the experience of personnel on a project. As the nation is about to face a tremendous decline in the experienced workforce due to the baby boomer generation’s retirement, it is critical to begin focusing on capturing their knowledge. Cataloging and communicating the knowledge of potential failures is critical to prevent engineering disasters. Many companies have adopted failure-reporting systems that allow them to record their engineering failures to promote failure prevention. While recording this information is vital to learning from past mistakes, often the information is not stored so that engineers and designers can easily recall this valuable linguistic information and use it to improve designs. Therefore, more effective systems for cataloging and utilizing corporate memory of recorded failure events are needed. This article presents the design of a computational linguistic database to support the failure prevention tool, the risk in early design (RED) method. RED promotes failure prevention by identifying failure risks as early as the conceptual phase of product design, where impacts of failure prevention are greatest. It uses a database populated by historical failure event information to present specific areas that are at risk of failure in a product.     

重型燃机定向结晶空心叶片凝固过程的实验与模拟

采用ProCAST软件系统研究HRS(High Rate Solidification)与LMC(Liquid Metal Cooling)工艺下,不同工艺参数对重型燃机用大型定向结晶空心叶片凝固过程的影响。结果表明:与HRS工艺相比,LMC工艺下叶片的糊状区宽度更小,固/液界面形状更加平直。LMC工艺下叶片的纵向温度梯度约为HRS工艺下的3倍;利用LMC工艺制备该燃机叶片时冷却速率为0.3~2.00℃/s,远高于HRS工艺时的冷却速率(0.05~0.16℃/s);LMC工艺下,采用低的保温炉温度仍可保证叶片获得高的温度梯度和冷却速率;而为避免缘板处杂晶对原始晶粒的阻碍,HRS工艺应当采用高的保温炉温度与更低的抽拉速率。实验与模拟结果均表明:与HRS工艺相比,利用LMC工艺制备的燃机叶片,枝晶组织显著细化。     

Life Enhancement of Gas Turbine Combustor Liner Through Thermal Barrier Coating

The life enhancement program of an aero gas turbine combustor liner has been taken up through thermal barrier coating. Yttria-stabilized zirconia with a composition of Zr₂O₂ + 8 wt.% Y₂O₃ has been applied by atmospheric plasma spray on newly manufactured liner. A remarkable improvement in liner life has been observed under severe service condition. However, peel off of coating is noticed on the serviced components which are premature withdrawn for any other reasons. Reason for peel off has been studied metallurgically in detail. Coated samples were subjected to cross-sectional microanalysis. Based on the microanalysis suitable repair procedures are being adopted for serviced components. The process found very effective for a better life.     

Failure Prevention Through the Cataloging of Successful Risk Mitigation Strategies

The objective of this paper is to introduce the method to add mitigation strategy data to the generated risk event effect neutralization (GREEN) method knowledgebase to improve its ability to effectively mitigate risks. Risk mitigation is the creation and selection of mitigation strategies to reduce, measure, or control risks in a system. Currently, a vast majority of risk mitigation strategies are created based on the engineering expertise of the engineers on a project. The GREEN method provides a means for engineers to supplement their experience by generating risk mitigation strategies based on past successful risk mitigation strategies using the failure modes of the potential risks that the product faces. In order to better aid the engineer in selecting the best possible risk mitigation strategy for a particular risk, more information on mitigation strategies needs to be cataloged in the GREEN knowledgebase. This paper outlines and demonstrates the method for adding new data on mitigation strategies to the knowledgebase, and presents a case study of how this information is added and used to mitigate product risks.     

某航空发动机涡轮叶片的断裂分析

某型航空发动机在外场服役过程中出现声音异常现象,地面检查发现高压1,2级涡轮叶片以及高压2级涡轮导向叶片全部折断。通过现场勘查、断口分析以及金相检查等手段,确认了由伸根梨形孔处断裂的高压1级涡轮叶片是该次失效的首断件,聚集分布的铸造疏松缺陷是引起其早期疲劳断裂的主要原因;其他各级涡轮叶片断裂均属二次损伤引起的过载断裂。