航空发动机用38CrMoAlA钢的耐蚀性及其力学性能

Corrosion Resistance and Mechanical Properties of 38CrMoAlA Steel for Aircraft Engines

  • 摘要: 在高温、高湿、高盐雾的海洋环境中,38CrMoAlA钢作为常用发动机传动轴材料,面临严重的腐蚀风险。针对某航空发动机鼓风传动轴的服役条件,进行了多周期湿热(7天)与盐雾(中性4天、酸性3天)交替腐蚀模拟试验。对不同周期的宏观形貌进行对比,采用失重法计算腐蚀速率,并对力学样品进行室温拉伸和疲劳极限测试。使用扫描电子显微镜(SEM)表征腐蚀产物的微观形貌和力学断口,元素成分分析采用能谱(EDS),并测量腐蚀坑深度。结果表明,经过5个周期后,基体被致密的腐蚀产物覆盖,表面出现大量腐蚀坑,腐蚀速率约为1.47mm/y;力学样品的强度、疲劳寿命和断裂韧性显著下降,中值疲劳极限降低约70%。这些结果为海洋环境中发动机零件的选材及防护措施提供了技术依据。

     

    Abstract: 38CrMoAlA steel is widely employed in critical components, including blower drive shafts of aircraft engines, due to its outstanding mechanical properties and surface hardening potential. However, in challenging marine environments characterized by high temperatures, humidity, and salt spray, this steel is vulnerable to severe corrosion, compromising its structural integrity and operational reliability. This study investigates the corrosion behavior and subsequent mechanical degradation of 38CrMoAlA steel under simulated service conditions, representative of an aircraft engine blower drive shaft operating in marine environments. A multi-cycle accelerated corrosion test was conducted, alternating between wet heat exposure for 7 days and salt spray exposure, including 4 days of neutral and 3 days of acidic salt spray, to replicate the extreme environmental conditions. To evaluate the material's degradation, we compared the macroscopic morphologies of steel samples at different stages of the test cycles, calculated corrosion rates using the weight loss method, and performed tensile and fatigue limit tests on the corroded mechanical specimens at room temperature. Scanning Electron Microscopy (SEM) was utilized to examine the microstructure of the corrosion products and the fracture surfaces of mechanical samples, revealing key insights into the material’s degradation at a microscopic level. Energy Dispersive Spectroscopy (EDS) was employed to analyze the elemental composition of the corrosion products, providing further understanding of the chemical processes driving corrosion. Additionally, a laser confocal microscope was used to measure the depth and distribution of corrosion pits, allowing us to quantify the extent of localized corrosion damage. The results indicated significant corrosion damage to 38CrMoAlA steel after exposure to the wet heat and salt spray cycles, with particularly deep corrosion pits emerging after the third cycle. The maximum pit depth was measured at approximately 560μm. After five cycles, the corrosion rate stabilized at around 1.47 mm/y, suggesting that the rate of corrosion slowed as corrosion products accumulated on the surface. Despite this, mechanical testing showed substantial deterioration in the material’s performance. Tensile strength, fatigue life, and fracture toughness were all significantly reduced, with the median fatigue limit decreasing by nearly 70%. The presence of corrosion pits and other surface defects contributed to accelerated crack initiation and propagation, severely impairing the steel's resistance to cyclic loading. These findings provide critical insights into the corrosion mechanisms and mechanical degradation of 38CrMoAlA steel in marine environments. They highlight the urgent need for advanced protective measures to mitigate corrosion and extend the service life of engine components. The data and analysis from this study offer a robust technical foundation for optimizing material selection and developing protective strategies for aircraft components exposed to harsh marine conditions, ensuring improved durability and reliability.

     

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