There are three basic reasons for vacuum processing of metals:
- Elimination of contamination from the processing environment
- Reduction of the level of impurities in the product
- Deposition with a minimum of impurities
Contamination from the processing environment includes the container for the metal and the gas phase surrounding the metal. In the vacuum process, impurities, particularly oxygen, nitrogen, hydrogen, and carbon, are released from the molten metal and pumped away; and metals, alloys, and compounds are deposited with a minimum of entrained impurities.