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

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.