Oxidation of MoSi₂-Coated and Uncoated TZM (Mo–0.5Ti–0.1Zr–0.02C) Alloys under High Temperature Plasma Flame

Abstract

Oxidation of coated and uncoated TZM alloys has been investigated under high temperature plasma flames with varying exposure time. TZM alloy specimens were pack-cemented in a powder mixture of Si, NaF and Al 2 O 3 (25, 5 and 70 mass%) in an Ar atmosphere at 1173 K, resulting in the formation of MoSi 2 and Mo 5 Si 3 layers on the TZM alloy. When the uncoated alloy was exposed to the flame for up to 4 min, the TZM alloy specimen showed a significant weight loss. However, the MoSi 2 -coated TZM alloy specimen did not exhibit a measureable weight loss during the same exposure time due to the presence of the MoSi 2 layer. The effect of coating layers on the oxidation of TZM alloy under the dynamic flame is discussed based on the surface morphology and the microstructural observations, together with the weight changes during the test.

Oxidation Behavior of MoSi2-Coated TZM Alloys during Isothermal Exposure at High Temperatures

“…At the same time, when the coated MoSi2 layer was exposed to high temperatures in the presence of air, the surface MoSi2 phase underwent a disintegration reaction, viz. (5/7) MoSi2 (s) + O2 (g) → (1/7) Mo5Si3 + SiO2 (s) [15]. This reaction shows that when the surface SiO2 layer was formed, an Mo5Si3 phase should be produced due to the loss of Si from MoSi2.…”

“…When a high-temperature SiF 2 activating gas atmosphere is formed through the heat treatment, Si is coated on TZM alloys through gas and solid state diffusion. The additional detailed coating procedure was described elsewhere [7,[12][13][14][15]. The outlook images of (a) as-received TZM; (b) the MoSi 2 -coated TZM; (c) the oxidized TZM without coatings; and (d) the oxidized TZM with Si pack cementation coatings exposed in air at 1350 • C for 50 h are shown in Figure 1.…”

“…Surface protection coatings such as thermal plasma spray, sputtering coatings, or pack cementation coatings have been studied in order to improve oxidation resistance at the exposure to high temperatures under an ambient atmosphere [8][9][10][11]. Among the coating routes, the pack cementation coating process has the capability of producing a uniform coating layer on complex shaped substrates, and is effective in preventing oxygen penetration [2,4,7,[12][13][14][15][16][17]. According to the literature, the formation of protective coating layers can be achieved by Si or Al pack cementation coatings [2,4,11].…”

Oxidation resistance of a Mo-W-Si-B alloy at 1000–1300 °C: The effect of a multicomponent Mo-Si-B coating

“…Recently, CVD coatings were shown to significantly prolong the lifetime of Mo-Si-B at 1300°C oxidative environment [24]. There are also other reports on the oxidation performance improvements resulting from the application of silicide coatings to Mo-base and other refractory metal alloys [25][26][27][28][29][30][31][32][33][34][35][36][37][38]. In this paper, we study the oxidation behavior of a coated and uncoated Mo-W-Si-B alloy.…”

Effect of Laser Surface Treatment on the Corrosion Behavior of FeCrAl-Coated TZM Alloy

“…However, a primary drawback of these alloys is susceptibility to high temperature oxidation because volatile MoO 3 is formed in the oxidizing environment at a high temperature such as 873˝C [2]. Therefore, some protective coatings are often necessary to protect the surface of Mo alloys from oxidation [3][4][5]. To this end, FeCrAl alloy can be applied as a coating layer to the surface of Mo alloys since it can withstand a temperature as high as 1400˝C [6,7].…”