extrusion screw banner

Alloys & Coatings

screwIt is important to choose the correct construction materials and coatings in order to maximize wear life and enhance process stability.

The majority of screws are still manufactured from nitriding steels but at Cooper Technology we offer a broad range of special alloys.

For highly abrasive or corrosive applications we offer an ‘Extreme Coating’ – typically an 88 % Tungsten Carbide HVOF deposit.

hvof gunThe Extreme Coating can fully encapsulate the screw or a ‘Flight Guard’ deposit can be applied to the screw OD only.

The coating is sprayed at supersonic speeds forming a true metallurgical bond. XC-1000 is the most common deposit.

It comprises 88 % Tungsten Carbide and 12 % Cobalt. This offers exceptional wear resistance. Other deposits are available including XC-9000 designed for sub-micron particle abrasion.

screwAfter deposition the Tungsten Carbide deposit is diamond ground to achieve finished OD tolerances and a surface finish ranging from +/- 140 RMS to 16-32 RMS.

The latter rivals chrome plating in appearance. Extreme Coatings are deposited by our colleagues at Surface Engineering in the US.


Screw Materials

We have a wide range of screw materials available, from the common nitriding steels to the latest high technology tool steels. Material choices include the following:

GP 100 A nitride hardened screw for undemanding applications. Good abrasion resistance with unfilled resins, but moderate corrosion resistance.
CP 200 A range of screw materials giving additional corrosion resistance. Small diameter screws are made from a stainless steel base alloy while larger screws are chrome plated.
TH 300 A through hardened tool steel screw offering excellent wear resistance and good corrosion resistance.
HP 400 A high technology tool steel with a very fine grain structure and a high percentage of Vanadium Carbides.  Suitable for processing heavily filled polymers at high screw speeds.
HP 500 S Generally as HP 400 but with a stainless steel matrix giving extra corrosion resistance, and a higher matrix hardness.
TC 600 A screw coated with Tungsten Carbide (either totally encapsulated or on the OD of the flights only) for severe abrasion applications.
FP 700 An iron free corrosion resistant alloy suitable for processing Fluoro-Polymers.


download For a full Technical Presentation, click here logo

Type Rc Descriptions
XC1000 Rc68/71 A composition of 12% Cobalt saturated with 88% 2-5 micron Tungsten Carbide with a particulate hardenss average of Rc82, providing ultimate abrasion resistance.
XC1000Ni Rc68/71 A composition 10% Nickel and 90% Tungsten Carbide providing ultimate abrasion resistance combined with improved corrosion resistance over the XC1000 in PVC applications.
XC1000-17 Rc67-70 A composition of 83% Tungsten Carbide and 17% Cobalt. Higher concentration of Cobalt provides improved ductilly.
XC4000 Rc55-65 A composition of Nickel, Chromium, and Chromium Carbide producing an abrasion resistant coating with extreme corrosion resistance and excellent ductility, relative to hardness.
XC9000 Rc65-70 Our Millennium Carbide is a Tungsten Carbide/ Cobalt featuring a unique sub-micron manufacturing process providing improved wear resistance over traditional Tungsten Carbide coatings. Excellent for sub-micron particle abrasion.


enquiryFor further information on extreme screw coatings, please complete the Enquiry Form.


Xaloy X-8000

X8000™ is a thermal spray coating applied to the screw. This material complements Xaloy’s high abrasive resistant X830 overlay and is well suited for processing highly filled or corrosive resins. It can be applied for the full flight length or only on isolated areas of the screw that are more susceptible to wear.


Xaloy X8000 screw coating


downloadDownload Xaloy X-8000 Datasheet.