Coating of metal balls - esp. steel balls used in mills or for highly stressed ball bearings

摘要

A vertical tube with a funnel-shaped upper end is fed from its bottom end with a stream of gas, flowing upwards to suspend a ball in the funnel while the coating is applied, esp. by thermal spraying with a stream of particles flowing at an inclined angle towards the ball. The ball is pref. made of steel, whereas the coating is pref. a hard metal, esp. a metal contg. tungsten carbide and applied via plasma spraying. The ball may also be suspended in gas while it is exposed to an electromagnetic field obtd. from an induction coil for heating to melt the surface of the ball and/or to bond the coating onto the ball, and/or to heat-treat the ball or coating; in all cases the gas stream is then used for cooling. Thich coatings can be economically applied to the ball without the need for special jigs.