Vacuum diffusion welding and vacuum brazing are two different welding methods.
Vacuum diffusion is a kind of welding method that is carried out in a vacuum, and the welds are closely bonded with each other. Under the appropriate temperature and pressure (workpiece bonding pressure), the welds are maintained for a period of time, so that the atoms are diffused between the contact surfaces, thus forming a connection.
Vacuum diffusion can be carried out between metals or between metals and ceramics.
Vacuum brazing: it is to use the liquidus temperature is lower than the base solidus temperature of solder metal materials, components and solder will be heated to melt solder, using liquid solder wetting parent metal, filling and joint clearance with parent metal dissolution and diffusion, and after that, the liquid crystal solidification of solder, so as to realize the connection of parts (is weldment not melting, is only solder melting).
Both can be welded in a vacuum or in a protective gas.