Coating Made for Better Wear Protection


A new nanoparticle coating for plasticating screws from Nordson Corporation (Westlake, OH) is said to offer improved abrasion and corrosion resistance compared to standard high-velocity oxygen fuel (HVOF) thermal spray.

The new Xaloy MPX thermal spray coating, developed by the company’s Polymer Processing Systems division in Neckarsulm, Germany, is made primarily of tungsten carbide particles only 5 microns in diameter, the manufacturer says.

These particles are six to seven times smaller than those in standard HVOF coatings and also more densely packed because of a uniform spherical shape produced in a controlled plasma process, it explains.

Nordson Corporation

A cross-section of the screw flight shows the new MPX coating (left); the reportedly improved wear resistance is said to result from a spray coating process that applies tungsten carbide particles only 5 microns in diameter (right), which are more densely packed because of their uniform spherical shape.

According to Nordson, the combination of ultra-fine particle size, higher coating density and a 2.5 times greater application velocity results in a stronger bond with the parent metal of the screw and improved resistance to wear.

Compared with standard HVOF tungsten carbide coatings, the company says the new coating technology exhibits:

  • 61 percent less mass loss in ASTM G65 abrasion testing;
  • 18 percent less mass loss in ASTM G77 sliding wear testing; and
  • 8.5 percent greater bond strength in ASTM C633 bond testing.

As an example of corrosion resistance, the Xaloy MPX coating survived more than 1,000 hours of salt fog testing, in part because of its near-zero porosity, according to the company.

Mark Colella, global product manager for the Xaloy brand, also says its higher bond strength eliminates potential for chipping.

“This new technology extends the working life of screws in extrusion and injection molding, enabling processors to work with some of today’s most challenging materials,” he adds.

Nordson recommends the Xaloy MPX technology for resisting abrasion from compounds with medium (15 to 35 percent) filler loadings and for resisting corrosion from halogenated materials, including flame retardants and PVC.

The new technology can be employed across the full range of screw diameters, it adds, and may be applied to the entire screw or to specific areas. Standard layer thickness is said to be 300 microns, with variations depending on the area of the screw.

The MPX screw coating should be used with a barrel lined with Nordson’s Xaloy X-800 nickel/tungsten carbide alloy or a comparable inlay, the company notes.

More information:


Tagged categories: Abrasion resistance; Asia Pacific; Coating Materials; Corrosion resistance; EMEA (Europe, Middle East and Africa); Galvanized/thermal spray coatings; Latin America; Metal coatings; Nordson; North America; Thermal spray

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