Method of making spray-formed articles using a polymeric mandrel

A method of making a ring-shaped article by spraying bulk material, comprising the steps of:

• preparing a hollow cylindrical polymeric mandrel having an. exterior surface and an inner surface receiving a pressurized fluid;
• thermally spraying molten metal particles onto said exterior surface of said mandrel, said particles applying a force and transferring heat to said exterior surface and melting said mandrel, said particles forming an initial layer having a porosity between 10 and 20% by volume and said molten polymer flowing into the interstices to form a metal-polymer composite layer;
• rotating said mandrel relative to said thermal spray particles to build said metal particles as multiple coatings on said mandrel;
• and
• applying a pressurized fluid to the inner surface of said mandrel;
• said particles softening said exterior surface of said plastic mandrel while said pressurized fluid both cools said mandrel and applies an internal pressure opposite to the force of said particles to resist the collapse of said mandrel from the heat and force of said particles.

A method of making a ring-shaped article by spraying bulk material, comprising the steps of:

• preparing a hollow cylindrical polymeric mandrel having an exterior surface, said mandrel having an inner surface receiving a pressurized fluid;
• spraying a first thermal spray layer of molten metal particles at a first temperature atop said exterior surface, said first thermally sprayed layer applying a force and transferring heat to said exterior surface and melting said polymeric mandrel, said first thermally sprayed layer having a porosity between 10 and 20% by volume and molten material from said polymeric mandrel flowing into the interstices to form a first metal-polymer composite layer;
• and
• applying succeeding thermally sprayed layers atop said first metal-polymer composite layer to form a succeeding layer having a porosity between 0.5 and 2% and being substantially free of polymeric material.