Effect of plasma-sprayed alumina on the strength, elastic modulus, and damping of Ti-25Al-10Nb-3V-1Mo intermetallic

The effect of a plasma-sprayed Al2O3 coating on the bend strength, elastic modulus, and damping of Ti-25Al-10Nb-3V-1Mo intermetallic substrate was measured. Two coating thicknesses of 0.1 and 1.0 mm were used in the study. The average strength and Weibull coefficients of the intermetallic samples coated with the 0.1 mm Al2O3 coating were very similar to those of the uncoated intermetallic samples. On the other hand, the average strength of the samples coated with 1.0 mm Al2O3 was significantly lower than the strength of the uncoated intermetallic substrate. The lower strength of the 1.0 mm coated samples was attributed to the higher volume fraction of the Al2O3 coating (which has a lower strength than the Ti-25Al-10Nb-3V-1Mo substrate) and higher porosity in the 1.0 mm coating. The Young's modulus and damping values of the 0.1 mm Al2O3-coated intermetallic did not vary significantly from those of the uncoated substrate. However, the damping values of the 1.0 mm Al2O3-coated intermetallics were significantly larger than those of the uncoated substrate. The higher damping values measured for the 1.0 mm Al2O3-coated samples were attributed to the higher porosity in the thicker coating and to defects in the coating as a result of the spraying process