WELDING RESEARCH Ni-WC differed from the filler metal used in the present study, this effect of Cr on WC dissolution is consistent with that shown in Fig. 20 based on thermodynamic analysis. Conclusions 1) The operation window for preparing a smooth cladding of Ni-WC without severe spatter is significantly wider with controlled-short-circuiting GMAW, i.e., GMAW-CSC, than with conventional GMAW. 2) The undesirable melting of the steel substrate, that is, the dilution of the hard Ni-WC cladding by the melted steel, can be better controlled with GMAW-CSC than with conventional GMAW. Increasing the heat input tends to increase dilution much more significantly with conventional GMAW than with GMAW-CSC. 3) The weaving pattern of the welding gun can significantly affect the uniformity of the thickness of the cladding and its dilution by the base metal. The optimum pattern can be found by using a low-cost 3D printer to move the workpiece under a stationary gun, which is especially convenient when a much more expensive welding robot or 3-axis CNC milling machine is unavailable. 4) High-resolution electron probe microanalysis (EPMA), with a very small electron beam of 80–100 nm in diameter, can allow the compositions of various phases in partially melted tungsten carbide particles and small W-rich interdendritic features to be determined. 5) As the heat input increases, which increases the partial melting of tungsten carbide particles during welding, the W-rich interdendritic features can change from essentially Nifree to containing 18–30 at-% Ni. 6) Thermodynamics analysis demonstrates that increasing the Cr content can cause Cr-containing carbide to form at the expense of the WC needed to provide the wear resistance. The authors would like to thank Dr. John H. Fournelle of the Department of Geoscience, UW-Madison for A B Fig. 18 — Compositions of interdendritic particles in singlebead cladding No. 47 (Fig. 7A) made with a lower heat input. A — Overview; B — enlarged. A C D Fig. 19 — Compositions of interdendritic particles in singlebead cladding No. 51 (Fig. 7C) made with a higher heat input. A — Overview; B, C, D — enlarged. 464-s WELDING JOURNAL / DECEMBER 2016, VOL. 95 B Acknowledgments
Welding Journal | December 2016
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