An introduction to the types of materials used in aerospace machining

In aerospace CNC machining, material selection is critical as these parts are exposed to harsh environments. Forrest Machining Inc machines and assembles components for the aerospace and commercial industries.

Not only must the materials used have extraordinary strength and durability, they must also meet specific criteria, such as weight, corrosion resistance, and high-temperature performance. Let’s take a look at some of the main materials that are integral to aerospace machining.

1.Carbon Steel

Carbon steel is highly valued in aerospace machining for its versatility and strength. It is primarily used to make structural components due to its high tensile strength and ability to withstand tremendous stress without deforming. The material’s robustness makes it ideal for making parts that are critical to the safety and stability of aerospace vehicles, such as landing gear assemblies and parts of aircraft frames.

2.Brass

Brass is another commonly used material in aerospace machining, especially for parts that require corrosion resistance and electrical conductivity. It is often chosen for electrical connectors, terminals, and housings in aerospace engineering.

The machinability of brass allows it to have precise dimensions and clean surfaces, which is essential for precise and high-risk aerospace applications.

3.Bronze

Bronze stands out in aerospace CNC machining for its corrosion resistance and resistance to metal fatigue. These properties make it suitable for bearings, bushings, and similar components that are subject to considerable mechanical wear and need to maintain a long service life under harsh operating conditions.
Bronze’s durability and strength ensure that these components can withstand the rigors of aerospace operations without frequent replacement.

4.Copper

Copper is indispensable in the aerospace industry due to its excellent thermal and electrical conductivity, making it a must-have material for cooling systems and electrical components. In aerospace CNC machining, copper is often used for heat exchangers, wiring, and other heat-dissipating components that play a key role in maintaining the operational integrity of aerospace systems. Its efficient ability to conduct heat helps manage the extreme temperature changes encountered during flight and space exploration missions.

5.Aluminum and Aluminum Alloys

Aluminum and its alloys have long been a staple in aerospace machining, prized for their light weight yet high strength. Aluminum alloys, especially those such as 7075, are favored for their high tensile strength and corrosion resistance. Much of this resistance is due to the oxide coating that forms naturally when aluminum is exposed to air, a property that greatly enhances its durability in harsh environmental conditions. 7075 alloy, with zinc as its primary alloying element, is not as easy to machine as other alloys, but it has extremely high fatigue strength. This makes it ideal for critical structural components such as wings, fuselages, and support structures.

Other aluminum alloys are also widely used, such as 4047, which can be used as a cladding or filler, 6951, which is often used in tail fins, and 6063, which is known for its structural applications. The 6000 series alloys are known for their machinability, making them a top choice for complex aerospace components that require precision and intricate machining capabilities.

6.Titanium and Titanium Alloys

Titanium alloys are indispensable in the aerospace industry, where the need for materials with excellent strength-to-weight ratios and outstanding performance at high temperatures is non-negotiable. Titanium’s strength and corrosion resistance make it a top choice for airframe and jet engine components, including disks, blades, shafts, and casings.

Titanium is used extensively in commercial and military aircraft, as evidenced by models such as the Airbus A380, Boeing B787, F-22, F/A-18, and UH-60 Black Hawk helicopters. These applications highlight the critical role of titanium in modern aerospace engineering. However, machining titanium presents unique challenges due to its high hardness, which can lead to increased tool wear and heat buildup.

To address these issues, aerospace machining often requires adjustments to the machining process, such as reducing machine speeds and increasing chip loads. Despite these challenges, advanced CNC machining equipment common in aerospace environments is well-equipped to handle titanium alloys, ensuring that the alloy’s benefits are fully utilized without compromising the quality or integrity of the machined parts.

7.Inconel Superalloys

Inconel superalloys, especially Inconel 718, play a vital role in aerospace machining due to their excellent heat resistance and high-temperature strength. Developed by Specialty Metals, Inconel 718 is a nickel-chromium-based superalloy designed for demanding applications. It was originally used in jet engine diffuser housings for the Pratt & Whitney J58 engine, which powers iconic aircraft such as the Lockheed SR-71 Blackbird.

The alloy’s properties are also used in modern aerospace projects, including SpaceX’s Falcon 9 launch vehicle, where it is used in the engine manifolds of the Merlin engine. Its use also extends to a variety of aerospace components, such as turbine blades, ductwork, and engine exhaust systems.

Machining Inconel 718 requires careful handling to minimize work hardening; therefore, it is typically machined using slow but aggressive cutting patterns, using hard tools to control its toughness and reduce tool wear. Despite these challenges, its excellent weldability and durability make it a top choice for aerospace applications, where reliability under extreme pressures and temperatures is critical.

8.Engineering Plastics

In addition to metals, the aerospace industry is increasingly relying on high-performance engineering plastics, such as PEEK, polycarbonate, and Ultem. These plastics are a valuable alternative to metals due to their lightweight and excellent mechanical properties, including impact and vibration resistance, sealing capabilities, and chemical resistance. They also have superior electrical insulation properties compared to metals, which is critical to the safety and functionality of aerospace applications.

Engineering plastics are used in a variety of aerospace components, from cabin interiors, such as tray tables and armrests, to critical operating components, such as insulation, piping, and valve components. These materials must meet stringent flame, smoke, and toxicity regulatory requirements to ensure safety in aerospace environments. Notable plastics used in aerospace CNC machining include Nylon 6, PEEK, Ultem, and PPS, each favored for their ability to meet specific performance standards required for commercial and military aerospace applications.