A Guide to Molybdenum CNC Machining

Key Takeaways

• Molybdenum is a rare refractory metal with a very high melting point, used both as an additive in steel and as a machining material.

• While machinable relative to other refractory metals, it is still classified as a difficult-to-cut material.

• Adding molybdenum to metals improves their hardness and impact resistance.

Overview

Molybdenum is a hard, silver-white metal compatible for CNC machining. It is sometimes used as an additive in steel, including certain stainless steels, to improve hardness and impact resistance. Pure molybdenum, with a purity of 99.90%–99.99%, is also used as a machining material.

Characteristics of Molybdenum

• Specific Gravity: 10.28

• Melting Point: ~2620°C (~4748°F)

• Boiling Point: ~4650°C (~8402°F)

Molybdenum has the fifth highest melting point among metals and is classified as a refractory metal, along with tungsten, tantalum, and niobium. Among these, molybdenum is less expensive than tungsten, retains high strength at elevated temperatures, and has a low coefficient of thermal expansion, giving it excellent shape stability at high temperatures.

Although it is difficult to cut, molybdenum has better machinability than other refractory metals. It is used in aerospace rocket parts, experimental automotive parts, and other applications.

Molybdenum Material Properties

Chemical Reactivity with Liquids

• Hydrochloric Acid: Slowly dissolves when heated.

• Sulfuric Acid: Slightly soluble in dilute solutions; slowly dissolves in concentrated acid up to 110°C (230°F); dissolves rapidly at 200°C (392°F) and above.

• Nitric Acid: Easily dissolves.

• Sodium Hydroxide: Largely unaffected by aqueous solutions, but reacts rapidly with molten acid.

Chemical Reactivity with Gases

• Water Vapor: Oxidation begins ~700°C (1292°F).

• Nitrogen: Embrittlement above 600°C (~1112°F); nitrides form above 1500°C (2732°F).

• Carbon Monoxide: Carbides form ~1000°C (1832°F).

• Carbon Dioxide: Oxides form at ~1200℃ (~2192°F).

• Hydrogen: No reaction.

• Hydrofluoric Acid: Slightly dissolves at room temperature.

• Chlorine: Forms chlorides at 250℃ (~482°F).

• Iodine: No reaction, even when red-hot.

• Ammonia: Slightly unreactive at room temperature.

• Hydrogen Sulfide: Forms sulfides at ~1200°C (2192°F).

Molybdenum can oxidize and delaminate in certain gas environments at high temperatures, so it is important to understand the operating environment and temperature range.

Molybdenum Machining

Molybdenum is a difficult-to-cut material that is hard but brittle, making it prone to chipping during machining. Specialized techniques are required, including:

• Assessing feasibility of machining different shapes.

• Determining proper cutting conditions.

• Using smooth processing procedures appropriate cutter feed rates.

• Selecting dedicated tools, such as specialized cutters.

Applications of Molybdenum

As an additive in steel: Enhances hardness, impact resistance, and deformation resistance to iron and is used for applications such as skyscrapers, highways, and industrial infrastructure.

High-performance parts: Thin sheets for automobiles and special composite materials for aircraft.

Catalysts: Used as a desulfurization catalyst in petroleum refining and as a catalyst and additive in the chemical industry, contributing to environmental protection.

Communication devices and electronic components: Like tungsten, molybdenum is widely used as an extremely stable material in a vacuum for electron tubes, light bulbs, vacuum furnaces, heaters, electrodes, and more. For improved functionality in these areas, challenges include achieving ultrafine particles and ultra-high purity.

Molybdenum Machining Experience

At Yumoto Electric, we provide end-to-end service for molybdenum, from material procurement to machining. Examples include small turned parts with diameters of φ3–φ4 mm (~0.12–0.16 in.) and lengths of 40 mm (~1.57 in.). Small-lot, short-lead-time machining is possible, even for difficult-to-cut materials like molybdenum.

Molybdenum is expensive and has low circulation. For example, a φ6 × 1000 mm (~0.24 in. × 39.4 in.) molybdenum round bar costs tens of thousands of yen, compared to a few hundred yen for an aluminum alloy bar. Procurement may take 4–5 days depending on size, so early confirmation is recommended.

Molybdenum CNC Machining at Yumoto Electric

Yumoto Electric delivers high-quality components fast, worldwide. We provide precision machining for a wide range of metals using milling, turning, and specialized metal processing. We have experience with over 200 materials including aluminum alloys, stainless steel, molybdenum, and titanium. 

If you’re unsure about material selection or machining methods, we offer complimentary consultations to help optimize your design and production. For any questions, please feel free to contact us.