In the last years there have been developed several consumables that deposit hard nanostructured iron-based metals with high resistance to abrasive wear. The erosive and abrasive wear resistances are mainly controlled by the chemical composition and the microstructure. In turn, the microstructure of the deposited metal usually shows variations with the experimental welding procedure, particularly related to the heat input. Also, the operating parameters that define the heat input (voltage, current and welding speed) affect aspects such as bead geometry (wide, penetration and reinforcement) and dilution with the base metal of the bead. The purpose of this work was to study the effect of heat input on the geometry of the bead, the dilution and the microstructural characteristics of a nanostructured iron-based alloy deposited by FCAW. Several samples with heat input between 0.5 and 3.5 kJ/mm were welded. Chemical composition was determined, microstructure was studied using both optical and electronic microscopy and X ray diffraction; hardness, grain size and percentage of dilution were measured. The microhardness of the deposit was found between 800 and 870 HV1, grain size variations were between 105 and 130 nm and the dilution ranged between 30 and 40%, depending on process variables used. The highest hardness and the lowest cristallite sizes were obtained with the lowest heat input, associated to a lower dilution.
hardfacing; nanomaterials; heat input; microstructure
