Depositing Ni-WC Wear Resistant Overlays with Hot-Wire Assist Technology
Hot-wire assist technology uses Joule (or resistance) heating to preheat the filler material to near its melting temperature before insertion to the weld pool. The advantage of using hot-wire technology over cold-fed wire is the reduced arc heat required to melt the consumable. The reduction of arc heat and weld pool temperature is essential for deposition of nickel tungsten carbide (Ni-WC) erosion resistant overlays. Tungsten carbide is prone to dissolution at elevated temperature in the matrix material, requiring a cold weld pool to increase the survivability of carbides during welding. Current research is utilizing tubular nickel sheathed tungsten carbide powder core wires in conjunction with Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW).
The Athabasca oil sands located in northern Alberta possess one of the largest deposits of oil in the world. The sticky bitumen must be extracted from highly abrasive quartz sand which rapidly degrades equipment in contact with the oil sands. Oil sands operators have chosen to protect ground engaging, crushing, screening, and hydrotransport equipment with Ni-WC overlays as it provides moderate impact resistance with high wear resistance. Ni-WC overlays are typically produced using the Plasma Transferred Arc Welding (PTAW) process utilizing nickel-based matrix and tungsten carbide powders. The large capital costs associated with PTAW and fixturing limits the overlay manufacturing to a few select organizations. The development of lower cost alternative welding process will enable smaller manufacturers to produce Ni-WC wear resistant overlays. Currently, hot-wire assisted technology has produced excellent quality overlays with comparable deposition rates to PTAW for a fraction of the capital costs. Ongoing research will hopefully improve both the quality and deposition rates of hot-wire assisted Ni-WC overlays.
- Stuart Guest, PhD candidate