All feedscrews are removed from service when the outside diameter has been reduced, which leads to a host of process issues (shear heat, increased residence time, poor heat transfer, high melt temperature, longer recovery times, reduced output rates, etc). This reduction in screw diameter results from metal-to-metal adhesive wear from the feedscrew contacting the barrel liner.
Extreme Coatings’ FliteGuard option protects the top of feedscrew fights with a layer of wear resistant tungsten carbide, that can improve screw life from three to tenfold compared to standard hard facing.
Our standard coating thicknesses are .005” (.125 mm) for screws of diameter 36 mm and below, and .010” (.25 mm) for larger feedscrews. Low heat input during the coating process ensures no post coating stress relief or straightening is necessary.
Our FliteGuard process is also an option to replace a small amount of wear on tool steel feedscrews. Most tool steel screws do not suffer from root- or flight-side wear, but eventually adhesive wear reduces their diameter. Tool steels cannot be weld repaired due to the alloy content of the screw, but we can apply up to .020” (.5 mm) to the tops of flights and return a worn screw to a like-new condition. Ask your supplier or Extreme Coatings about this option.
This cutaway shows our protective layer uniformity on the flight land or OD only
A short case study of FliteGuard results:
A 2-1/2” barrier screw with C56 hard facing and chrome plating operating 16/6 for 12 months has .035” (.85 mm) of diameter reduction.
Coating with .020” overall (.50 mm) and operating the same schedule resulted in .005” total wear (.125 mm) in 20 months of operation.
After 44 months of operation, maximum wear had reached .017” (.45 mm). This is more than seven times less wear with Extreme Coatings, and four times the service life.
FliteGuard is an especially good option for large extrusion feedscrews. The reduced wear on the diameter provides higher total throughput (more total lbs/hr) and less downtime to remove and repair or replace feedscrews.