Titanium Alloy vs. Stainless Steel: Scratching the Surface of Durability

23 September 23

In a recent video uploaded by the YouTube channel TechRax, the durability of the iPhone 15 Pro was put to the test, and the results raised eyebrows. The iPhone 15 Pro, boasting a titanium alloy frame, was subjected to a scratch resistance test and appeared to perform less impressively than its predecessor, the iPhone 14 Pro, which featured a stainless steel frame. This unexpected outcome prompts the question: why does the titanium alloy frame seem to have inferior scratch resistance compared to the stainless steel frame?

Understanding Titanium Alloy:
Titanium alloys are a group of materials made from a combination of titanium and other metals. Titanium itself is a crucial structural metal developed in the 1950s, renowned for its high strength, excellent corrosion resistance, and resistance to high temperatures. Over the decades, various types of titanium alloys have been developed, including high-temperature titanium alloys for aircraft engines and structural titanium alloys for aerospace applications.

Among the hundreds of known titanium alloys, some of the most well-known include Ti-6Al-4V, Ti-5Al-2.5Sn, Ti-2Al-2.5Zr, Ti-32Mo, Ti-6242, Ti-Mo-Ni, Ti-Pd, SP-700, Ti-10-5-3, Ti-1023, BT9, BT20, IMI829, and IMI834, each with its unique properties and applications.

The Resilience of Stainless Steel:
Stainless steel, on the other hand, is an alloy primarily composed of iron and various elements such as nickel, chromium, molybdenum, and carbon. What sets stainless steel apart is its impressive corrosion resistance. Elements like nickel and chromium form a passive oxide layer on the surface of stainless steel, preventing rust and giving it that characteristic shine. Unlike regular steel, stainless steel’s lustrous finish is highly resistant to tarnishing, earning it the name “stainless.”

The composition of stainless steel varies, with different proportions of iron, nickel, chromium, molybdenum, and carbon (among others) determining its type or grade. This composition influences properties such as the strength of the protective oxide layer, resistance to specific corrosive substances, and various mechanical properties like hardness, melting point, and shear modulus.

The Mystery of Scratch Resistance:
So, why did the titanium alloy frame of the iPhone 15 Pro seemingly succumb to scratches more readily than the stainless steel frame of its predecessor? The answer lies in the inherent characteristics of these materials.

Titanium alloys, while incredibly strong and lightweight, have certain properties that may make them more prone to scratching. Their lower thermal conductivity means they can heat up during machining, possibly affecting their hardness. Additionally, titanium alloys can react with cutting tools, potentially leading to abrasion and scratching during machining processes.

Stainless steel, with its better machinability, tends to produce smaller chips and is less susceptible to work hardening during machining. This could explain why it appeared to outperform titanium alloy in a scratch resistance test.

The choice between titanium alloy and stainless steel for a frame or structural component depends on various factors, including strength, corrosion resistance, and aesthetic considerations. While titanium alloys excel in many areas, such as aerospace applications, they may require careful handling to avoid scratching. Stainless steel, with its superior scratch resistance, remains an excellent choice for a wide range of products, from consumer electronics to kitchen utensils.

In the case of the iPhone 15 Pro, the mystery surrounding the scratch resistance may boil down to the specific type of titanium alloy used, the machining process, and the surface treatment. Each material has its strengths and weaknesses, and choosing the right one depends on the intended application and the desired balance of properties. As materials science and manufacturing techniques continue to advance, the quest for the ideal balance of durability, aesthetics, and performance will undoubtedly persist.

At CNC Machining China Factory, we have rich experience in CNC machining of both titanium alloy and stainless steel for a wide variety of industries. You can rely on our complete CNC machining capabilities for your custom CNC machining projects with quality and timeframe guaranteed.

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