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The multi-billion dollar energy, mining, and construction industries in Canada rely heavily on equipment protection for improving equipment life cycles. Protection against erosion and corrosion is often accomplished through the use of a weld overlay on the equipment surface. Chromium carbide overlays (CCO鈥檚) are a cost effective wear resistant overlay that drastically improves the equipment life cycles over plain carbon steels. CCO overlays are commonly deposited with arc welding processes such as Flux-Cored Arc Welding (FCAW) and Submerged Arc Welding (SAW). Common uses of CCO鈥檚 include chutes, hoppers, sizing screens, and bucket liners. The work discussed in this report focuses on the SAW welding process and the use of recent power supply advancements for improved CCO wear performance.

The wear resistant properties of chromium carbide overlays result from high concentrations of Cr and C in the weld deposit, promoting nucleation and precipitation of high fractions of hard M7C3 carbide phases. The formation of the wear resistant carbide phase is intrinsically linked to the balance of Cr and C in the deposit. A trademark of the SAW process is large weld penetration, leading to significant dilution of the high Cr-C deposit with the low-alloy steel plate. The subsequent drop in Cr and C concentration leads to lower fractions of M7C3 and poor wear performance. The development of alternating current (AC) SAW power supplies has given control of weld pool dilution through the balance of DCEP/DCEN polarities. The work discussed will look at the effect of polarity balance on the amount of dilution, volume fraction of M7C3 carbide phase, overlay hardness, and heat input in the weld deposit. It was found that the use of AC waveforms improves the overlay properties over traditional DCEP SAW weld deposits. The potential application of AC waveforms on CCO wear resistant overlays for industrial scale production is discussed.