Influence of Heat Input on Microstructure in Multicomponents (Cr, Mo, W, Nb, C, B) Fe-Based Nanostructured Hardfacings

Abstract:

Surfacing welding is an issue that was increasing in relevance in last years, related with a raising number of applications in several industries. Hardfacings of nanostructured multicomponent steel of recent creation, have a set of outstanding properties. Nevertheless, the information available related with its processing is still scarce. The aim of this work was to analyze the influence of heat input on the dilution, microstructure and microhardness of a Fe-based nanostructured alloy with complex carbides. Eight bead on plate samples were welded using heat inputs between 0.5 and 3.5 kJ/mm. The dimensional study was performed as well as chemical composition and percentage of dilution with the base metal were determined and the microstructure was analyzed using optical and electronic microscopy and X-ray diffraction. Microhardness was also measured. It was observed that dilution varied between 28 to 34% according to the heat input. The microstructure was formed primarily by α-Fe with metallic carboborides (M₇(BC)₃, M₂₃(BC)₆) and niobium carbide (NbC). It could be seen that the size of precipitates increased with the increasing heat input. The bead hardness varied with heat input from 800 HV₂ for 3.5 kJ/mm to 970 HV2 for 0.5 kJ/mm.

Key-words:
Hardfacing welding; FCAW; Nanostructured materials; Heat input; Microstructure