Thermal Oxidation of Tungsten‐Based Sputtered Coatings

Abstract

The effect of the addition of nickel, titanium, and nitrogen on the air oxidation behavior of W‐based sputtered coatings in the temperature range 600 to 800°C was studied. In some cases these additions significantly improved the oxidation resistance of the tungsten coatings. As reported for bulk tungsten, all the coatings studied were oxidized by layers following a parabolic law. Besides WO3 and WOx phases detected in all the oxidized coatings, TiO2 and NiWO4 were also detected for W‐Ti and W‐Ni films, respectively. WOx was present as an inner protective compact layer covered by the porous WO3 oxide. The best oxidation resistance was found for W‐Ti and W‐N‐Ni coatings which also presented the highest activation energies ( Enormala=234 and 218 kJ mol−1 respectively, as opposed to Enormala≈188 kJ mol−1 for the other coatings). These lower oxidation weight gains were attributed to the greater difficulty of the inward diffusion of oxygen ions for W‐Ti films, owing to the formation of fine particles of TiO2 , and the formation of the external, more protective layer of NiWO4 for W‐N‐Ni coatings.

The role of nickel in the oxidation resistance of tungsten-based alloys

“…In comparison with previous results [1], this study confirms that the presence of nickel improves the oxidation resistance of W-(N ) sputtered coatings. The improvement is higher for higher nickel contents.…”

“…This behaviour, found previously for the oxidation of W-C-Ni [3], suggests two different mechanisms for oxide growth in agreement with that presented above. The first values are close to those determined for the oxidation of single-phase tungsten and W-N sputtered films [1]. The second values should be attributed to the diffusion of Ni2+ through the NiO or NiWO 4 , or the diffusion of W6+ through NiWO 4 .…”

“…Deposition technique oxide layers grow on the surface of tungsten sputtered films when they are oxidised in air in the temperature The films were deposited by direct-current (DC ) range 600 to 800°C. It was demonstrated that the reactive magnetron sputtering with a specific target oxidation resistance of this sputtered film could be power density of 10 W cm−2 and a negative substrate increased by alloying it with other transition metals bias of 70 V. To complement the series of W-N-Ni (nickel or titanium) and/or interstitial elements (carbon coatings previously described [1], the W−10 wt% Ni or nitrogen). In the case of nickel, two coatings were target was used in reactive mode and two more films studied: one without nitrogen and a very small nickel were deposited with an N 2 /Ar partial pressure ratio of content showing a crystalline body-centred cubic (bcc) 1/4 and 1/3, for a total deposition pressure of 0.3 Pa. a-W structure and the other, amorphous, with nitrogen…”

“…Owing to the rotational movement of the coatings showed a much better oxidation resistance than substrate holder, all the faces were uniformly coated. W-N/C and W-N/C-Ti films [1][2][3].…”

Oxidation of Ni films electroplated on steel

“…In spite of extensive works carried out on the high temperature oxidation of Ni and Ni-based alloys [1,2], very little is known about oxidation of thin Ni films. Ni-W [3], W-N-Ni [4], Ni-WC [5], and Ni-derivatives [6] are continuously being developed as wear-and corrosion-resistant films. Hence, study on the oxidation behavior of Ni films is imperative to understand the fundamental aspects concerning the oxidation of various Ni-containing films.…”