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Can anyone suggest a coating or plating for this application?

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APPLICATION:
Various thermoplatics (e.g. PE,PP,PS) will be melted in A 4130 DOM steel
tube and then a 304 stainless steel piston will be pressed into the tube
to extrude the melted plastics from the tube (via a nozzle orifice
press-fitted into one end of the tube).

PARAMETERS:

Temperature range of tube: 300-650 F
Temperature range of piston: 100-550 F
Size of stainless piston: 8"L x .625"Diameter
Size of steel tube: 5"L x .63 ID (nominal)

OBJECTIVE:
1)To minimize potential sticking of the thermoplastics to the
piston and the tube.
2)Low COF
3)Helps protect surfaces from corrosion and rust.

PREFERENCE (not critical): colorless coating for the stainless rod

Thanks in advance for any responses.

Jay Braun
R&D - Allentown, Pennsylvania, USA

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I would prefer electroless nickel with teflon particles, TiN or thin dense chrome. All are very effective but none is cheap or easy to find.

Guillermo Marrufo
Monterrey, NL, Mexico