440C stainless steel (UNS S44004) is the hardest available stainless steel after heat treatment.

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Although 440C has the highest carbon content, the alloy retains its status as a stainless steel alloy thanks to the chromium content in the material composition.

About 440C:

As a commercial engineering material, 440C stainless is more readily available than 440B - the material benefits from high strength and hardness combined with medium wear resistance. After heat treatment, 440C is the hardest stainless steel available. Other popular grades in this series include 440A, which offers superior toughness, while 440F is a free machining option.

Suitability:

The alloy finds suitability in various commercial engineering applications for markets from general engineering and fabrication to aerospace and motorsport. Motorsport applications include valve parts, bearings, bushes and pressure relief valves.

Machining:

The alloy is straightforward to machine once annealed, although a suitable chip breaker will be needed. Once hardened, any machining operations are pretty much impossible. 440C should not be used in heat-resistant applications above the alloy's tempering temperature.

About SHP:

Smiths High Performance is a leading stockholder and supplier of high-performance engineering materials. We are material supply chain partners supporting high-technology motorsport market sectors, including Formula 1 and MotoGP.