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| Author | Topic: coating on screw |
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gllemoine Senior Member Posts: 12 |
posted December 06, 2004 07:29 AM
   
Hi, I would like to know in order wich are the best type of coating to have on a extrusion screw. The resin extruded are LLDPE,LDPE and HMWHDPE for blown film extrusion. Thank you IP: Logged |
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Ron Member Posts: 1 |
posted December 16, 2004 08:44 PM
By "coatings" I assume you are referring to hardfacing on the screw flights and platings or treatments on the screw root diameters. In the past the most common hardfacings were cobalt based but now they are nickel based. Such as Colmonoy #56. Tungsten based hardfacings are also quite popular such as Colmonoy # 83 and 88 etc. There are several specialty processes for root diameters or total encapsulation of the feed screw. But unless your screws are in a highly abrasive inviromentment and wear out in less than six months they are cost prohibited. Relatively small screws can be made out of CPM-9V or other grades of tool steels. Ion Nitriding is another treatment that can offer a lot of wear protection. With or without hardfacing flights. Screws subject to excessive corrosion are better constructed from Hastelloy, 440C or Inconel. However hardened Nickel plating can also be an excellent choice. By far Industrial Hard Chrome is still the plating of choice mainly for root diameters. It makes the screws easier to clean, offer a fair about of abrasion or corrosion protection is reasonable price and looks good! For your requirements I would think Colmonoy #56 for your LLDPE and LDPE applications would work fine and Colmonoy #88 for your HMWHPE. Plus chrome plating but make sure it is at least .001" thick or you will be wasting your money. Regards, Ron Anderson IP: Logged |
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