304 stainless steel brazing incorporating tungsten nanoparticles

Tungsten nanoparticles of 80nm average particle size were utilized in the brazing of 304 stainless-steels. The nanoparticles were characterized by DTA and TEM, and the brazed samples were evaluated by SEM and Vickers microhardness tests. The interaction of the tungsten nanoparticles with the metallic filler in the melting zone modified the size and morphology of the formed phases into a finer and uniformly distributed microstructure. In samples treated at 1200°C for 60min, the microhardness decreased from 310 to 170HV, being the latter value, close to that of the base metal. The nanoparticles and the microcracks develop a synergistic effect when they are in contact with the liquid phase in such a way that a rise in the threshold capillary-pressure leads to the filling of the interstices. The capillary-like system resulting from the wettability of the nanoparticles and microcrack surfaces by the liquid phase, leads to a solidified microstructure with fine and uniform phase distribution.