An overlay of Tungsten Carbide-Cobalt-Chromium, a High Velocity Oxygen Fuel Coating, are applied to a variety of process rolls in order to extend the service life and to maintain profiles and pocket shapes for maximum efficiency. Industries such as food processing, pharmaceuticals, manufacturing, and recycling make use of this high performance overlay.
Process Rolls are the workers of industry. They often use pressure and heat to reduce sizes of various stock from thick steel plate to aluminum foil. Specialized rolls use profiles and pockets to form pellets, briquettes, fingers, and balls from materials that range from corundum to candy. Rolls are used to force materials into specific shapes or through sizing screens for reclassifying or recycling. Early process rolls were usually chilled cast iron with a surface hardness of Rc 40. Later, alloy materials were used to develop greater hardness after heat treating. Other treatments such as nitriding, carburizing and cryogenic hardening did not require the high alloy substrates which can be expensive. Chromium electroplating became environmentally unfriendly.
Diamalloy 5849 is an economical tungsten-carbide 10% cobalt 4% chromium powder. Diamalloy 5849 is especially suited for applications where simultaneous wear and corrosion resistance is required. Chromium in the matrix improves the corrosion resistance while maintaining the abrasive, erosive, and fretting wear properties of tungsten carbide-cobalt based materials.The Rockwell Hardness equivalent of the overlay is Rc 65-70 and the bond strength is greater than 12,000 PSI which is greater than all other thermal spray coatings.
Process rolls of all types are hardfaced with HVOF tungsten- carbide for original equipment manufacturing and overhaul of components. These coatings offer an environmentally safer, cleaner, and less expensive alternative to chromium plating.