Electron beam welding molybdenum to obtain vacuum tight weld - where joint is coated with other metals before welding

摘要

The joints are made by welding two pts. made of Mo (1) or between a Mo pt. and a pt. made of another metal or alloy (2). The novelty is that the zones to be welded are coated with another metal (3) which can form an alloy with metals (1,2) during welding. Metal (3) pref. consists of a film obtd. from a metal-organic cpd. e.g. Ru-, Re-, or Pt chelate. Alternatively the two pts. may be coated with aq. OsO4 soln. and briefly annealed in H2 to obtain a film (3) of Os. Metal (3) may also be obtd. using a metal powder mixed with an organic binder to form a paste. Used e.g. in mfg. electron tubes. Mo is expensive so components are frequently made by welding Mo strip to avoid turning parts from solid bar, or by welding Mo to other metals to reduce costs. Avoids intercrystalline cracking which occurs with conventional welding techniques.