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

Abstract

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 treatment 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.

Microstructure and cavitation erosion performance of nickel-Inconel 718 composite coatings produced with cold spray

“…13f) due to the localized cyclic loading and the pressure oscillation. The latter remark complies with the fatigue nature of the cavitation erosion as has been also reported by other researchers [62][63][64].…”

Study of Surface Modification of Niobium Caused by Nitriding and Cathodic Cage Deposition

“…However, the PN treatments caused diffraction peak displacement due to the insertion of nitrogen in the niobium matrix (Nb -ISCD 76416). According to Kertscher et al 23 , o the solvus curve for the α-Nb(N) phase, the solubility of nitrogen in niobium bcc ranges from < 3 wt% N at a temperature of ≈ 2350 °C to zero at room temperature 23 . Therefore, the low amount of nitrogen in the niobium matrix caused peak shifts of little significance.…”

Effects of the Voltage and Pressure on the Carburizing of Martensitic Stainless Steel in Pulsed DC Glow Discharge

“…Concerning the influence of the processing parameters studied here, the literature is rich for austenitic stainless steels (ASSs) plasma nitriding [19][20][21][22][23][24][25][26][27][28][29] , but very poor for MSSs, being mainly focused on treated surface characteristics of different materials, through different processes [30][31][32][33][34][35][36][37][38][39][40] . It is to be noted that almost nothing has been published aiming to study such effects on the MSSs LTPC.…”