Matriz ferrítica reforçada com TiC-NTC/Fe2Ti formados em cordão simples soldado por GTAW: microestrutura, dureza e resistência ao desgaste

Abstract

Arc welding coatings based on metal matrix nanocomposites reinforced with carbon nanotubes (CNTs) have demonstrated improvements in steel hardness, however, physical metallurgy and tribological phenomena are still little discussed in the literature. In this sense, this research evaluated the microstructure, hardness and wear resistance of weld metals (WM) without/with CNT. For this, carbon steel tubular wires filled with Ti6Al4V/CaF2 or NTC/Ti6Al4V/CaF2 powders (mass ratios of 40:4 and 1:40:4, respectively) were deposited on an A131 D steel plate by GTAW at 160 A. Microstructural and X-ray diffraction analyses confirm the formation of Fe-α + Fe2Ti + TiC in the WM with CNT and the detection of Raman bands D, G and G’ evidence its partial transformation into the TiC phase, increasing the degree of amorphous carbon by 38.86% (compared to the nanotubes as received). In the cross and top sections, the hardness of the MS with CNT was, respectively, 126.93% and 47.76% higher than that without CNT. And, despite the close average coefficients of friction (0.54 and 0.55, respectively), the wear depth with NTC was 123.93% lower, showing that that hardness, self-lubrication, and heat dissipation mitigate material removal. Thus, TiC-NTC/Fe2Ti can act as reinforcement in the coating of tool steels.