Influence of niobium on the microstructure and wear resistance of iron-based hardfacings produced by pre-placement technique—a novel approach

This study introduces a novel approach to produce hardfaced alloys via pre-placement technique using the shielded metal arc welding process. The comparison between the microstructural, mechanical, and tribological properties of the Nb-free and Nb-additive hardfacings was characterized by optical microscopy, X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray mapping, dry sliding wear, and hardness measurements. From the optical microscopy results, it was observed that the hardfacing alloys obtained by pre-placement technique with premixed powders are free of pores or cracks and show good metallurgical bonding with the substrate. SEM images revealed that the Nb-additive alloys are comprised of net-like carbides in interdendritic region and NbC particles in the matrix with a grain size ranges from 0.5–2 μm, which were found to be beneficial for enhanced hardness and wear resistance. Nb-additive alloy showed 2.63% increase in wear resistance in comparison with the Nb-free hardfacing. It has shown possible to obtain the high hardness and wear-resistant hardfacings with pre-placement technique.