Plastics with modified characteristics play an increasingly important role in the industry. Mineral additives or glass fibres in particular are very demanding on the wear resilience of the plasticising components. Austrian injection molding machinery maker ENGEL recently unveiled a carbide coating for screws under the "ENGEL onyx" product name. According to the company, the carbide coating improved both the coating toughness and the bonding force by 300% while showing improvements of abrasion resilience. Carbide metal coated plasticising screws are said to be essential for processing technical composites with a high additive level to achieve economically viable lifecycles. The carbide coating ensures the required abrasion resilience; the underlying steel handles the mechanical loads, and guarantees a high level of safety in case of impact stress due to excellent strength characteristics.
The company maintains the unique selling point of the new ENGEL onyx carbide metal coating is the evenly spread coating of carbide metal over the whole screw contour and its extremely high bonding potential. In a drop hammer impact test, the maximum drop impact force before initial cracking occurred was up to 300 percent higher compared to other coating systems. Additionally, the annealing process was considerably improved to boost bonding force. While standard HVOF (High Velocity Oxygen Fuel) coatings achieve bonding levels of just 90 to 110 MPa, the ENGEL onyx coating system achieves bonding values of 250 to 350 MPa. The company says due to the onyx wear protection system for plasticising screws, screw channel geometry is more or less stable due to the low level of wear, thus enabling a stable process window for extended periods of time even in the processing of plastics with a high additive content.