Stainless Steel

418 Stainless Steel

Specs: AMS 5616
UNS#: S41800

418 stainless steel, also referred to as Greek Ascoloy, is an ideal choice for demanding applications that require durability and high-temperature performance. Designed to meet the challenges of extreme environments, this Chromium-Nickel-Tungsten martensitic stainless steel thrives in service temperatures up to 1200°F, making it a standout material for industrial needs.

Mechanical Properties

Tensile strength: After hardening and tempering, tensile strength can exceed 1,000 MPa.

Hardness: When heat-treated, this alloy achieves a Rockwell hardness of approximately 40-50 HRC.

Toughness: Despite its high hardness, it absorbs energy under impact without fracturing.

Chemical Composition

The alloy’s uniqueness comes from its carefully balanced chemical composition. Chromium, composing 12–14 percent of the material, provides excellent corrosion and oxidation resistance, even at high temperatures. It also forms a stable passive oxide layer that enhances durability.

Nickel, at 1.25–2.5 percent, makes it tougher and helps the alloy handle stress and impact, particularly in low-temperature conditions. Additionally, nickel boosts resistance to thermal fatigue.

Tungsten, comprising 0.5–1.0 percent, strengthens the alloy and enhances wear resistance, especially under high-temperature conditions. It also helps the material retain hardness during demanding operations, making it reliable for tough environments.

Heat Treatment Process

Hardening and tempering determine the performance of 418 steel. During hardening, the alloy is heated to a temperature of 1742–1886°F and then rapidly quenched in air or oil. This process transforms the microstructure into martensite, a phase known for its exceptional strength and hardness.

Following hardening, the steel undergoes tempering, where it is reheated to a lower temperature, typically between 392–1202°F, and held for a specific period. Tempering relieves internal stresses from the hardening process while enhancing toughness and ductility. By carefully adjusting the tempering temperature, manufacturers can achieve the desired balance between hardness and toughness.

Strength and Durability

Boasting impressive resistance to scaling and oxidation at temperatures reaching 1400°F, 418 stainless steel delivers outstanding durability in demanding conditions where other materials may falter. It retains its structural integrity against oxidizing agents, atmospheric corrosion, and weak organic acids, with heightened durability when hardened and tempered. This makes it a top choice across industries where corrosion resistance and strength are critical.

Versatile Applications

Applications for this exceptional alloy range from steam turbine buckets and blades to gas turbine compressor parts, highlighting its reliability in high-stress, high-temperature environments. Additionally, it is commonly used in fabricating high-temperature bolts, where its robust properties ensure long-lasting performance and resistance to deformation under extreme conditions. The versatility of 418 steel doesn’t end there; its availability in round and square shapes provides engineers and manufacturers with the flexibility to meet specific design requirements.

How 418 Steel Excels

One of the most compelling reasons to choose 418 stainless steel is its balance of toughness and resilience at elevated temperatures. While many materials weaken under intense heat, this alloy maintains superior mechanical properties, giving it an edge in aerospace, energy, and power generation. Its resistance to thermal fatigue and oxidation enhances the longevity of components crafted from this alloy, providing reliable operation and reduced maintenance demands throughout its use.

Available shapes – round and square

Tools

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