Microstructural aspects and mechanical behavior of hardfacing deposited by FCAW

Several sorts of hardfacings has been used as a method of combating wear to increase equipment life cycle, reduce costs with maintenance stops, parts recovery and replacement. This work evaluates the incidence of cracking, microstructural characteristics and the mechanical behavior of FeCrC and FeCrC + Nb hardfacing alloys, deposited by self-shielded flux-cored arc welding (FCAW-S) process on SAE 1020 steel sheets. Single layer and double layer coatings were produced for both alloys in two interpass temperatures conditions, at room temperature and preheat of 250 degrees. By liquid penetrant inspection, a lower incidence of cracks was observed to FeCrC + Nb alloy. The microstructures of all FeCrC alloy coatings presented large primary M7C3 carbides in a hexagonal and needle-shaped morphology on a matrix of a eutectic mixture of austenite and carbides. For FeCrC+Nb alloy single layer coatings, a microstructure with large niobium carbides (NbC) and few primary M7C3 carbides, both being surrounded by eutectic of austenite and carbides. However, for FeCrC+Nb alloy double layer coatings, microstructures indicate NbC carbides along with large and frequent M7C3 carbides, most of them in a needle-shape morphology and a few in a hexagonal shape, being surrounded by a eutectic mixture of austenite and thin M7C3 carbides. Microhardness was superior for FeCrC alloy, due to the predominance and morphology of the primary M7C3 carbides shown and the refinement promoted by Nb.