Molybdenum (Mo

Alloying Element – Molybdenum

Molybdenum (often nicknamed “Moly”), like chromium, affects the corrosion resistance of steel. Molybdenum also increases the hardenability, toughness, and tensile strength of steel. The hardenability is increased by lowering the required quench rate during heat treatment. Molybdenum also decreased the risk of pitting (PRE) by improving resistance to chloride.

• In Steel (up to 6% ): Moly, is a powerful hardenability agent and is a constituent of many heat treatable alloy steels. It decreases softening at high temperatures. Hence it is used in boiler and pressure vessels and high-speed steel. In common alloy steels such as 4340, it has a content of around 0.25%. In high-speed steel, in ranges between 3%-6%.
• In Stainless Steel (up to 30%): When amounts of chromium around 11% or greater are used, and nickel composition is higher than 8%, austenitic stainless steel is created. The chromium forms a thin film of reaction products that shields the metal substrate from oxidation attack. The protective film (called passive film) is only 1.0-2.0 nm, reducing the corrosion rate to a negligible level. Typical stainless alloys such as 316 have 17% chromium content.
• In Super Alloys (Up to 50%): Where stainless steels may fail is where nickel-based superalloys come into play. Most HSRA’s contain around 20% of chromium (For example, Inconel 718).
• In Aluminium Alloys (Up to 0.5%): Chromium is added in small quantities to Aluminium alloys to control the grain structure and prevent recrystallization. It also reduces stress corrosion y and improves toughness. Although it is a small quantity, it is critical for high-quality Aluminium.

Raw Materials by Molybdenum content