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Application of Cu70Ni30 Alloy in Aircraft Landing Gear Buffer Components—Impact Resistance and Fatigue Resistance, Overcoming the Challenges of Pure Metals

Aircraft landing gear is a core component for aircraft landing and taxiing. Buffer components (such as shock absorber pistons, springs, and bushings) are responsible for absorbing the enormous impact loads during landing, mitigating vibrations, and protecting the aircraft fuselage and core systems. They must possess extremely high impact resistance, fatigue resistance, corrosion resistance, and dimensional stability, and withstand repeated impact loads over long periods in high and low temperature environments ranging from -55℃ to 150℃ without failure. Pure metals, as traditional buffer component materials, are either impact-resistant but have poor fatigue resistance, or have good corrosion resistance but insufficient strength, making them unsuitable for the harsh operating conditions of landing gear buffer components. Copper 70-Ni 30 alloy(Cu70-Ni30, with a mass ratio of 70% copper and 30% nickel), with its excellent impact resistance, fatigue resistance, and comprehensive performance, has become the preferred material for aircraft landing gear buffer components, driving the upgrade of aircraft landing gear towards higher reliability and longer service life.

In aircraft landing gear buffer components, the performance limitations of various pure metals are extremely prominent, making it difficult to meet the requirements of repeated impacts and long-term stable service. Pure steel is a commonly used pure metal material for traditional buffer components. It has high strength, good impact resistance, and can withstand huge landing impact loads. It is also inexpensive and can be used in auxiliary structures such as buffer housings. However, pure steel has poor fatigue resistance. Under long-term repeated impact loads, it is prone to fatigue cracks. In actual tests, the average life of pure steel buffer springs is only 5,000 landing cycles. Furthermore, it has extremely poor corrosion resistance and is prone to rusting in humid and salt spray environments, leading to component jamming and reduced buffering effectiveness. Therefore, it can only be used in landing gear buffer components of low- to mid-range aircraft.

Pure aluminum has a low density and good machinability, offering advantages in lightweight design. It was once considered for use in auxiliary structures of cushioning components. However, pure aluminum has extremely low strength and poor impact resistance, making it unable to withstand the massive impact loads during landing. It is prone to deformation and fracture, and its fatigue resistance is extremely poor; repeated impacts result in plastic deformation, rendering it completely unsuitable for the core structure of cushioning components. Pure copper has good machinability and flexibility, allowing it to be made into simple components such as cushioning bushings. However, pure copper has poor impact resistance and fatigue resistance, easily showing wear and deformation from repeated impacts over time. Furthermore, its insufficient corrosion resistance makes it susceptible to corrosion, limiting its use to low-pressure, low-impact auxiliary cushioning components.

Pure titanium boasts excellent corrosion resistance, high strength, and good impact resistance, making it suitable for high-end landing gear buffer components. However, pure titanium is difficult and expensive to process, costing 3-4 times more than Cu70Ni30 Alloy. Furthermore, pure titanium has moderate fatigue resistance, making it prone to fatigue cracks from repeated impacts. Controlling processing precision is difficult, and dimensional tolerances easily exceed the precision requirements of buffer components. Therefore, it can only be used in landing gear buffer components for a niche range of high-end military aircraft, hindering large-scale application. Pure nickel offers good corrosion resistance but moderate fatigue resistance, insufficient impact resistance, and high density with poor processing performance, making it unsuitable for complex-shaped buffer components and limiting its use to auxiliary sealing structures. Pure tungsten exhibits outstanding impact resistance, but its brittleness and high processing difficulty prevent the fabrication of flexible buffer components. Its high density also contradicts the trend towards lightweight design, rendering it completely unsuitable for landing gear buffer requirements.

Compared to various pure metals, the core advantage of the Cu70Ni30 Alloy lies in its synergistic optimization of impact resistance, fatigue resistance, corrosion resistance, and dimensional stability. Its 70% copper and 30% nickel mass ratio precisely matches the operational requirements of the cushioning components—the addition of nickel significantly enhances the alloy's fatigue resistance and impact resistance, while copper ensures its flexibility and machinability. This synergistic effect completely solves the problem of pure metals being "impact-resistant but fatigue-resistant, corrosion-resistant but impact-resistant." The alloy's impact toughness reaches 180 J/cm², far superior to pure steel (100 J/cm²) and pure titanium (150 J/cm²), enabling it to withstand the enormous impact loads during landing without deformation or fracture, providing stable cushioning performance.

In terms of fatigue resistance, the Cu70Ni30 Alloy exhibits a fatigue strength exceeding 250 MPa, significantly higher than pure steel (180 MPa) and pure copper (100 MPa). Under repeated impact loads (10⁶ cycles), it shows no fatigue cracks or stress relaxation, extending its service life by 4-6 times compared to pure steel landing gear components, reaching over 20,000 landing cycles. This substantially reduces the replacement frequency and maintenance costs of landing gear components. Regarding corrosion resistance, a dense oxide film forms on the alloy surface, effectively resisting corrosion from moisture, salt spray, hydraulic oil, and other corrosive media. In actual tests, the Cu70Ni30 Alloy landing gear component, after 10 years of service in a simulated aircraft landing gear environment, showed a corrosion rate of only 0.01 mm/a, with no pitting or cracking. Its corrosion resistance is far superior to pure steel and pure copper, and comparable to pure titanium.

Furthermore, the Cu70Ni30 Alloy exhibits excellent dimensional stability, with a thermal expansion coefficient of only 13 × 10⁻⁶/K. During high and low temperature cycling from -55℃ to 150℃, the dimensional change is ≤0.002mm, ensuring the fitting accuracy of the buffer components and preventing a decrease in buffering effect due to dimensional variations. This alloy also boasts excellent machinability, allowing for the fabrication of complex-shaped buffer components such as buffer pistons, buffer springs, and bushings through forging, stamping, and precision machining. The high machining accuracy, with dimensional tolerances controllable within ±0.005mm, enables precise fitment with other landing gear components. Moreover, the processing cost is more than 60% lower than pure titanium, facilitating mass production.

Meanwhile, the Cu70Ni30 Alloy has a density of 8.9 g/cm³, which is 12% lighter than pure steel and 25% lighter than pure copper. While maintaining performance, it can effectively reduce the overall weight of the landing gear, aligning with the trend of lightweighting in aviation. It is estimated that using Cu70Ni30 Alloy to manufacture buffer components can reduce the weight of a single passenger aircraft by approximately 80 kg and improve flight fuel efficiency by more than 6%. Currently, this alloy has been applied to the landing gear buffer systems of aircraft such as the Boeing 737, Airbus A320, and domestically produced C919 and Y-20. China has achieved independent production of aviation-grade copper-70 nickel-30 alloy buffer components, with product performance reaching international advanced levels.

However, there are still shortcomings that need further development: First, the fatigue resistance at high temperatures can be further improved; under long-term use at 150℃, the fatigue strength will show a slight decrease. Second, the processing efficiency of complex-shaped buffer components is relatively low, and production costs need to be optimized. In the future, by adding trace amounts of chromium and manganese to improve high-temperature fatigue resistance and by improving precision machining processes, the Cu70Ni30 Alloy is expected to be extended to more advanced aircraft landing gear buffer systems, completely replacing pure metals and driving the development of aircraft landing gear towards greater reliability, longer lifespan, and lighter weight.

AlloyHit specializes in producing Cu70Ni30 products in various specifications, such as Cu70Ni30 Sheets, Cu70Ni30 Rods, Cu70Ni30 Wires and Cu70Ni30 Tubes.