15-5PH vs 4340 – What’s the Difference?

You might have heard about 15-5 PH and 4340 steel grades, but do you know their differences? Both steels are used in various applications and industries, including aerospace, marine, and chemical processing. However, each has unique properties that make them suited for specific applications. This blog post will explore the differences between 15-5 PH and 4340 steel, their characteristics, benefits, and drawbacks.

Difference between 15-5PH And 4340

15-5 PH steel, also known as stainless steel grade 15-5 PH, is a high-strength, corrosion-resistant alloy that contains 15% of chromium and 5% nickel. It is precipitation-hardening stainless steel that can be heat-treated to increase strength and hardness. 15-5 PH steel is ideal for applications that require high strength, toughness, and resistance to corrosion and wear. It is commonly used in the aerospace industry for components such as landing gear, engine parts, and structural parts, as well as in manufacturing chemical processing equipment and nuclear reactor components.

On the other hand, 4340 steel is a low-alloy, high-strength steel alloyed with chromium, molybdenum, and nickel. It has high tensile strength, toughness, and fatigue resistance. Its hardness can be increased through heat treatment, making it suitable for high-stress applications such as gears, shafts, and axles in the aerospace, automotive, and oil and gas industries. 4340 Steel is also used in producing machinery, forging dies, and mining equipment due to its excellent performance in high-temperature, high-pressure, and corrosive environments.

One of the main differences between 15-5 PH and 4340 steel is their corrosion resistance. 15-5 PH steel is a stainless steel designed to resist corrosion, especially in harsh environments with exposure to chemicals, acids, and seawater. It has excellent resistance to stress corrosion cracking and hydrogen embrittlement. In contrast, 4340 steel is not stainless steel, requiring coatings and platings to protect it from corrosion. Its corrosion resistance is better than 15-5 PH steel but is still adequate for many applications.

Another difference between 15-5 PH and 4340 steel is their machinability. 15-5 PH steel has good machinability, allowing easy shaping, drilling, and cutting. It can be easily welded, brazed, and soldered. However, due to its precipitation-hardening process, it requires specialized heat-treating equipment and techniques. In contrast, 4340 steel has poor machinability due to its high hardness and toughness, requiring specialized machining tools and drilling, milling, and grinding techniques.

Lastly, 15-5 PH and 4340 steel prices differ significantly. 15-5 PH steel is more expensive than 4340 steel due to its higher nickel and chromium content and its production method. It is a specialized alloy that requires precise chemical composition and heat treatment to achieve its desired properties, making it more costly. In contrast, 4340 steel is a lower-cost alternative to most high-strength steels, making it widely used in industry. For more information visit MarketsMartb2b


In summary, the differences between 15-5 PH and 4340 steel lie primarily in their chemical composition, corrosion resistance, machinability, and cost. Both steels are versatile materials with high strength, toughness, and fatigue resistance. The choice between them depends on the application’s specific requirements, such as the need for corrosion resistance, machining ease, and cost-effectiveness. Understanding the differences between 15-5 PH and 4340 steel can help you make the right decision for your industrial or commercial project.

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