Screw protection | machinery
main wear mode, according to Tom Kvinge, marketing manager at Extreme Coatings. “Our thermal spray coatings have almost no porosity so they protect from highly corrosive materials like CPVC, fluoropolymers, and halogen-free flame retardants,” he says. The company initially offered only complete encapsu- lation of a feed screw surface, but says that not all processors require this level of protection. Its Flite- Guard system for extrusion screws provides a coating on just the flight tops. “FliteGuard is a great option where adhesive wear is the main mode of wear,” says Kvinge. “FliteGuard can also be used to bring a worn tool steel screw back to dimension. Usually tool steel (particle metallurgy or highly alloyed D2 steels) cannot be weld repaired. FliteGuard is a great option to put these expensive screws back into service.” The company also offers CarbideX CPR (Chrome Plating Replacement) thermal spray coating, which it says is considerably better than hard chrome plating (HCP) for screws and rotors in equipment processing PVC. The company says corrosive fumes created in PVC processing permeate the micro-cracks and pores in
HCP. “In the past, HCP was the primary option for PVC and CPVC [but] HCP does not provide adequate protection of the base material, ultimately leading to premature wear, excessive scrap and downtime.” CarbideX CPR is a blend of carbon and chromium in a
nickel matrix. According to the supplier, it is applied two to three times thicker (0.8 – 0.1 mm) and more uniformly than standard HCP and fully encapsulates the entire working surface of the screw. “It is difficult to deposit a
Above: Application of a wear resistant coating at Extreme Coatings
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