The influence of small additions of Ni, Ti and C on the oxidation behaviour of sputtered tungsten coatings

Abstract

The oxidation rate of sputtered tungsten-based coatings, oxidised in air at temperatures of 6008C±8008C can be in¯uenced signi®cantly by the addition of small amounts of nickel, titanium and carbon. The presence of carbon does not change the type of oxide phases formed during the oxidation of sputtered W coatings: there are two oxide layers, the inner being a compact sub-oxide of WO x type and the outer being a typical porous WO 3 phases. The addition of Ni and Ti, however gives rise, in addition to WO x and WO 3 , of other type of oxides, such as NiWO 4 and TiO 2 , respectively. The oxidation process is very complex, with different¯uxes of species to be considered: the oxygen ion¯ux from the exterior to the interior, and Ni and Fe diffusing towards the exterior. At the annealing temperature of 8008C, in the cases of W±C±Ni ®lms, a FeWO 4 layer is detected beneath the mixed oxide. The greatest oxidation resistance is obtained for W±C±Ti, followed by W±C±Ni and ®nally W±C. # .pt (A. Cavaleiro) 0924-0136/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 4 -0 1 3 6 ( 9 9 ) 0 0 2 2 2 -8

Study of W/WC films produced by plasma assisted vacuum arc discharge

“…For 600 °C oxidation temperature, the coatings present incipient oxidation with weight gains of less than 0.25 mg cm 2 . As expected, when the temperature increases, greater oxidation rates were observed [18].…”

High Purity Tungsten Spherical Particle Preparation From WC-Co Spent Hard Scrap

“…2 (a). Dense WC and Co phase mixture is transformed to porous WO 3 and CoWO 4 phase mixture by isothermal oxidation process owing to high Pilling-Bedworth ratio of components [3] and CO 2 gas formation [4]. When it comes to the isothermal oxidation kinetics, WC-Co showed a linear oxidation behavior and the kinetic parameter is increased with isothermal oxidation temperature increasing.…”

“…CaWO 4 was dissolved in hydrochloric acid and tungstic acid was obtained. Dehydrated WO 3 was reduced by hydrogen in a reducing furnace at C for hours. Tungsten particle was spheroidized by RF thermal plasma process as following the experimental condition of Table 1.…”