Electron beam physical vapor deposition apparatus

An electron beam physical vapor deposition coating apparatus comprising:

• a coating chamber at a first subatmospheric pressure;
• a hood defining a coating region within the coating chamber, the coating region containing a coating material, the coating region being operable at an elevated temperature and a second subatmospheric pressure greater than the first subatmospheric pressure within the coating chamber;
• means for introducing gases into the coating region within the hood;
• an electron beam gun projecting an electron beam into the coating region and onto the coating material, the electron beam gun being operable to melt the coating material and to evaporate molten coating material;
• means for supporting an article in the coating region so that vapors of the coating material deposit on the article;
• a first aperture in a wall of the coating chamber through which the electron beam passes before entering the coating chamber;
• a second aperture in a wall of the hood through which the electron beam passes before entering the coating region, the second aperture having been formed by cutting the hood with the electron beam so that the second aperture has a cross-section corresponding to the electron beam to assist the introducing means in maintaining the coating region at the second subatmospheric pressure;
• a second chamber between the wall of the coating chamber and the wall of the hood, the second chamber enclosing the first aperture so as to separate the first aperture from the coating chamber and the coating region;
• and means for maintaining the second chamber at a pressure lower than the first subatmospheric pressure within the coating region.