What is the Best Metal for Aerospace Parts? Aluminum vs Stainless Steel vs Titanium
The aerospace industry has some of the toughest part and material requirements. Aerospace parts need to be extremely strong, lightweight, and highly resistant to environmental changes.
A Boeing 747 has roughly 6 million individual parts. The materials used for the parts vary depending on the use case, but the three primary metals used are aluminum, stainless steel, and titanium.
These alloys have some of the best strength to weight ratios, and corrosion resistant properties. This article will explain different pros and cons of each and help you decide which metal might be the best for your aerospace parts.
Aluminum for Aerospace parts
Aluminum is one of the most-used metals for precision machined parts. It’s relatively inexpensive, lightweight, and has great machinability. Aluminum has been used in the aerospace industry since the very beginning.
Aluminum also has great corrosion resistance, and it can easily be anodized, painted, and heat treated to increase the resistance in harsh environments.
In recent years, aluminum parts have been replaced by strong polymers and honeycomb structures to further reduce weight. Aluminum alloys still make up around 20% of aircraft parts, and it will be used for the foreseeable future.
There are 3 main categories of aluminum alloys used in the aerospace industry.
2000 series aluminum is a weaker aluminum, so it’s mostly used in decorative parts that don’t require great strength or corrosion resistance.
6000 and 7000 aluminum alloys have much greater strength and are used for structural parts, and parts that require better corrosion resistance. 7075 aluminum is more expensive, but it’s very easy to machine, and it increases in strength in low temperatures which is ideal for many aircraft parts.
Material Cost Factor: 2/10
Machining Cost Factor: 1/10
Pros and cons of aluminum
- Lightweight
- Inexpensive
- Resistant to corrosion
- Less expensive to machine
- Can be alloyed or treated to increase strength and corrosion resistance
- Lower strength and temperature resistance
Stainless steel for Aerospace parts
Stainless steel is another metal that’s used for millions of different precision parts in many industries. Stainless steel contains a minimum of 10.5% chromium, and the strength of the alloy can be increased by adding more chromium.
Stainless steel parts are significantly heavier, so they’re more commonly used where greater strength is necessary and heavier parts aren’t a big factor.
Compared to aluminum, stainless steel is much stronger and maintains its strength in wide temperature fluctuations. It is more expensive to machine, but the parts are less prone to physical wear and tear, so the lifetime of stainless steel is longer.
There are many different stainless steel alloys available—each with slightly different physical attributes. The most commonly used alloys for aircraft parts are 303 and 304 stainless steel. Both of these have a lower material cost and lower machining cost, while maintaining strength and corrosion resistance.
Material Cost Factor: 3/10
Machining Cost Factor: 4/10
Pros and cons of stainless steel
- Higher resistance to corrosion
- Better temperature resistance
- Stronger and more resistant to physical wear
- Heavier than aluminum and titanium
- More expensive material and machining
Titanium for Aerospace parts
Titanium is a premium metal, but its characteristics make it ideal for many aerospace parts. Titanium has the best strength-to-weight ratio, and it’s stronger than stainless steel in environments where there are extreme temperature changes.
The biggest downside to using titanium is the cost. It’s significantly more expensive as a raw material, and more expensive to machine. That means it’s only used in situations that require a better, more durable material.
Titanium is about 50% as dense as stainless steel, and it provides the same amount of strength as stainless steel at 40% of its weight. Titanium has the benefits of being lightweight like aluminum, without losing the strength that stainless steel offers.
Titanium alloys are roughly 15x more expensive than stainless steel, and cost 2.2x more to machine. However, the benefits that titanium provides can be ideal for aerospace parts that require the combination of strength and weight reduction.
The two most common titanium alloys are Grade 6 and Grade 23. Grade 23 titanium has higher oxygen content resulting in more ductility and fracture resistance than Grade 6, but it’s slightly weaker.
Material Cost Factor: 9/10
Machining Cost Factor: 8/10
Pros and cons of titanium
- Most expensive material and machining
- More prone to scratches
- Stronger when temperatures fluctuate
- Best strength to weight ratio
Picking the right material for your parts can be challenging, so our team is available to help you choose. We have decades of experience using all sorts of different metal alloys, and we have machined various parts for aerospace projects.
Here are a few general guidelines to help:
Use aluminum when:
- Cost is a major factor
- Weight reduction is important
- Parts don’t need extreme strength
Use stainless steel when:
- Strength is more important than weight reduction
- Parts need to handle greater pressure and high temperatures
Use titanium when:
- Reducing costs isn’t a big factor
- Strength and weight reduction are a high priority
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