First Results of Cavitation Erosion Behavior of Plasma Nitrided Niobium: Surface Modification

Ricardo Kertscher, Juliana Martins de Moraes, Sérgio Henke, Angela Nardelli Allenstein, Regis Henrique Gonçalves e Silva, Jair Carlos Dutra, Silvio Francisco Brunatto
2015 Materials Research  
This work presents the first results of the plasma nitriding study performed in pure niobium in order to increase its cavitation erosion resistance. Samples were prepared from 98.9% purity and 90% reduction cold-rolled niobium bars. Annealing treatment of the cold-worked niobium samples was carried out in vacuum furnace at 1.33 Pa pressure, in the temperature of 1000 °C, for a time of 60 min. Annealed samples showing hardness of 80 HV were cut to dimensions of 20 × 30 × 4 mm 3 . Nitriding
more » ... ent was conducted at 1080 °C, gas mixture of 90% N 2 + 10% H 2 , flow rate of 5 × 10 -6 Nm 3 s -1 , and pressure of 1200 Pa (9 Torr), for a total time of 4 h comprised by two treatment steps of 2 h each. For comparison purpose, results for nitrided and non-nitrided niobium are confronted. Samples were characterized by XRD, nanoindentation, microhardness, SEM, and 2D surface topography and 3D interferometry profile analysis techniques. Cavitation testing was conducted according to ASTM G32-09. Comparatively, promising results based on the formation of niobium nitride phases in treated surfaces are presented and discussed in the present work.
doi:10.1590/1516-1439.027515 fatcat:ounhqh4gq5hyljns4cjyilbysy