Bimetallic screws are used in order to extend the life of screws, specially by processing abrasive polymers.
Bimetallic screws are thus called because they are made up of two or more metals. When combined, they reinforce the most sensitive parts subject to wear.
The usual manufacturing programme of Talleres Pena consists of applying an alloy on the crests of screw threads by welding. This alloy can be resistant to abrasion, corrosion or both at the same time.
PPTA Process
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The screw is manufactured, leaving a channel on the top of flight (area that touches with the cylinder).
Through the P.T.A. machine the chosen alloy is deposited on the channel
Once deposited the grinding edges and the diameter will be grinded.
Once deposited the grinding edges and the diameter will be grinded.
The alloys used are the ones on the market, such as stellite G1, stellite G6, stellite G12, Colmonoy 56, Colmonoy 83, etc.
Or alloys specially designed for generic or specific applications:
Fe Cr Mo V alloy with excellent resistance to abrasion under high pressure. Good resistance to corrosion. Allows nitriding treatment reaching a hardness of 1100 Hv.
Ni Cr W alloy with excellent resistance to abrasion and corrosion.
Ni Cr alloy with 35% WC added to the base of outstanding resistance to abrasion and good resistance to corrosion.