Effects of PTA Torch Selection on Microstructure and Performance of WC-MMC Overlays

Minimizing wear of mining components in the oil sands industry is key to increasing productivity and decreasing excessive maintenance costs.  A significant amount of research has gone into the selection of appropriate materials for improved wear protection.  Tungsten carbide overlays are applied to the most critical components, typically by plasma transferred arc welding (PTA-W).  This study aims at investigating the effects of several commercial PTA torches in terms of overlay microstructure and performance.  A commercial tungsten carbide-NiCrBSi metal matrix composite (MMC) was used as the overlay material. 

A variety of parameters were studied when comparing the torches; including heat input, powder delivery, and deposition pattern.  The effect of the overlay microstructure was examined using both optical and scanning electron microscopy.  The overlay performance was gaged using dry sand abrasion testing (G65).