Oxidation response of Al coated TZM alloys under dynamic plasma flame

The oxidation response of TZM alloys has been investigated at the exposure of dynamic plasma flame with a variation of exposure time. In order to examine the effect of pack cementation coatings, aluminum coatings on TZM alloys have been carried out with a powder mixture of Al, NH4Cl and Al2O3 (25:5:70 wt.%), resulting that molybdenum aluminides (~ 200 μm) were synthesized on the surface of TZM. When the TZM alloys were exposed in the dynamic plasma flame, the temperature of the specimen was increased up to 1550 °C. While a significant weight loss was observed for the uncoated TZM alloy due to a volatile MoO3 phase formation, the Al coated TZM alloys did not exhibit any weight loss during the exposure of the flame. It appears that the excellent oxidation resistance is attributed to the Al2O3 formation during the flame tests. The oxidation stability of the coated and uncoated TZM alloys has been discussed in terms of weight changes and structural evolution.

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► Molybdenum aluminides were synthesized after Al diffusion coatings.
► No weight changes were observed for the Al coated TZM during oxidation.
► The produced alumina served as oxidation protection and thermal barrier layer.