Revestimentos ricos em Nb aplicados sobre aço microligado por soldagem a arco

Abstract

The current world scenario portrays a situation of global shortage of raw materials and an increase in their prices. The economies that already yearned for more durable parts and equipment, in this panorama need even more engineering solution to increase the useful life or to suppress the wear and tear of these parts and equipment. Based on this, this study sought to combine surface engineering with welding engineering in an attempt to obtain a niobium-rich coating through submerged arc welding deposition, as this is a technique that allows high deposition rates, great technical simplicity and relatively low cost. This research consisted of adding a FeNbC alloy in percentages of 5, 10, 15, 20 and 30% by weight to a basic commercial flow. This mixture was added as a flux in submerged arc welding as a way of transporting Nb to the microstructure of the coating and trying to improve the mechanical properties and resistance to abrasive wear. To characterize the coating, microstructural characteristics were analyzed, such as the presence of the coating phases, with the aid of optical microscopy and scanning electron; microhardness through a Vickers micro-durometer and characteristics of resistance to abrasive wear, such as loss of mass with the aid of a rubber wheel type abrasometer and the wear mechanisms evaluated by scanning electron microscopy. The results showed success in obtaining the coatings, as well as that they formed a microstructure rich in Fe2Nb and NbC. The formation of Nb-rich phases increased the microhardness of the coatings, with increments of up to 120%, and also increased the ability to resist abrasive wear to values higher than the microalloyed steel that was the base metal. There were changes in the mechanisms of abrasive wear, which without the addition of Nb were predominantly due to plastic deformation, and when added up to 15% of FeNbC they became by micro-cutting and micro-plowing.