Oxidation Behavior of Tribaloy T-800 Alloy at 800 and 1,000 °C

Abstract

The oxidation behavior of Co-based Tribaloy T-800 alloy has been studied isothermally in air at 800 and 1,000°C, respectively. The results showed that the oxidation mechanism was dependent on the exposure temperature. The oxidation of the alloy followed subparabolic oxidation kinetics at 800°C. The oxide scale at this temperature exhibited a multi-layered structure including an outer layer of Co oxide, a layer composed of complex oxide and spinel, a nonuniform Mo-rich oxide layer, an intermediate mixed oxides layer and an internal attacked layer with different protrusions into Laves phase. During 1,000°C exposure, it followed linear kinetics. The oxidation rendered a relatively uniform external Cr-rich oxide layer coupled with a thin layer of spinel on the top surface and voids at local scale/alloy interface and intergranular region together with internal Si oxide at 1,000°C.

Oxidation mechanism of cobalt based alloy at high temperatures (800–1100°C)

“…[16][17][18][19] The E a value and the XRD results and SEM-EDS analyses are in accordance with a scale growth mechanism limited by a Cr 2 O 3 scale acting as a compact and adherent diffusion barrier under isothermal conditions. The present results are very different from those obtained by Zhang 12 because the alloying element content of the alloy T-800 is very different from the Phynox one.…”

“…Zhang et al have studied the oxidation behaviour of a Co based Tribaloy T-800 [Co-17?5Cr-28?5Mo-3?4Si (wt-%)] exposed isothermally in air at 800 and 1000uC. 12 Results have indicated that the oxidation mechanism was dependent on the exposure temperature. The oxidation of the alloy followed subparabolic oxidation kinetics at 800uC.…”

“…The addition of iron induces only minor changes in the corrosion and oxidation resistance. Zhang et al have studied the oxidation behaviour of a Co based Tribaloy T-800 [Co–17·5Cr–28·5Mo–3·4Si (wt-%)] exposed isothermally in air at 800 and 1000°C 12. Results have indicated that the oxidation mechanism was dependent on the exposure temperature.…”

A Novel Oxide Layer Formed on the 800 °C-Annealed CoMoCrSi Coating Significantly Reduced Friction and Wear at Room Temperature

“…The Co Tribaloy alloy (similar to T-800) (8.5% Mo-17.5% Cr-3.4% Si) has a hardness of up to 1000-1200 HV because of hard ternary Laves phase, e.g., Co 3 Mo 2 Si or CoMoSi [13]. In addition, Mo and Si in the alloy can improve the high temperature strength and wear performance of the alloy, and Cr contributes to high oxidation resistance by means of the formation of Cr 2 O 3 layer [14,15]. However, recent studies [16][17][18] showed that CoMoCrSi coatings usually exhibited an amorphous microstructure, which resulted in brittle and low plastic performance at room temperature 2 of 17 (RT).…”

Isothermal oxidation behavior of TribaloyTM T400 and T800

“…Although high temperature oxidation behavior of chromiaforming alloys has been extensively investigated, [11][12][13][14][15][16][17][18][19] little attention has been paid to the oxidation resistance of T400 and T800 alloys. The oxidation behavior of T400 was studied by do Nascimento et al 20 at 450 and 750°C in air for 6 h and Sliney & Jacobson 21 at 650°C for 20 h. Zhang et al [22][23][24][25] studied the isothermal oxidation behavior of T800 23 and T800 modified with additions of rhenium, 24 yttrium and aluminum, 25 and iron and aluminum 22 in air at 800°C and 1000°C for up to 60 h. The oxidation behavior of an alloy strongly depends on time and temperature of exposure. It has been frequently shown that predicting long-term oxidation behavior on the basis of short-term results can be misleading.…”