Molybdenum is a element
with symbol ‘Mo’ and atomic number 42. Its name has been derived from Neo-Latin
word ‘molybdaenum’ meaning lead, and was discovered in 1781 by Carl Wilhelm
Scheele. It does not occur naturally as a free metal, and only found in
different oxidation states. Machining
molybdenum can be done through common metal machining processes, and
therefore, no individual methods or equipments are required to produce parts
with accurate dimensions.
• Tools for machining molybdenum: For machining molybdenum, tools should be sharp, firmly chucked and well supported. The machines should be sufficiently powerful, rigid and free from backlash. Tools life is shorter than expected as molybdenum is more abrasive than other metals. It has the tendency to chip while being machined.
• Lubricants: Machining is done without lubrication, but if they are used, the tool life can be increased and so do the cutting speed. It helps in removing fine molybdenum particles from the tools. Use of lubricants makes the various high- chlorinated oils and solvents effective in various processes of band saw cutting, turning, in reaming, drilling, tapping and in hacksaw. Sulfur-based cutting oils cannot be used in machining, electronic parts because of their poisonous effect on final properties.
• Sawing and shearing: Sawing molybdenum is the practice of that used for super alloys. The use of a soluble oil, coolant is the band saw or hacksaw cut removes the chips and lengthens the blade life. The most efficient blades used for sawing are high speed steel blades with only one tooth area.
• Milling and shaping: Milling and shaping of molybdenum is done with carbide grading tools which are normally used for casting iron. Face Milling is effective for machining plain surfaces.
• Drilling reaming and threading: Two- lipped carbide drill is generally used for drilling. Cutting oil should be used for all the tapping, reaming and drilling purposes. Reaming is a very difficult process, the tool life is very low as compared to the other machining processes. Threading can be done in various ways. Thread cutting with single tool is one of the most popular ways.
• Electropolishing and photoetching: The Electropolishing of molybdenum is done using two most commonly used acids- Sulphuric acid and phosphoric acid. They both provide better finishing. The baths using these acids are done under room temperature with molybdenum as anode. The photoetching process mainly done by conventional methods. It is either done chemically or electrolytically.
