Microstructural Evaluation of the Zirconia Plasma Sprayed Coating on Ti-6Al-4V Alloy after Creep Test
The titanium affinity by oxygen is one of main factors that limit the application of their alloys as structural materials at high temperatures. The objective of this work was evaluating the microstructure of the of the zirconia plasma sprayed coating Ti-6Al-4V alloy in creep test. Yttria (8 wt.%) stabilized zirconia (YSZ) (Metco 204B-NS) with a CoNiCrAlY bond coat (AMDRY 995C) was atmospherically plasma sprayed on Ti-6Al-4V substrates by Sulzer Metco. Constant load creep tests were conducted with Ti-6Al-4V alloy in air and in nitrogen atmospheres in uncoated samples and in air in coated samples at stress level of 56 MPa at 700°C. The microstructural analyze show that the predominant mechanism in the test conditions was characterized by formation and coalescence of micro cavities with shape and size varieties. The cavities are corrugated in discontinue regions, like inclusions and points involving dislocation. The size and shape of dimples are governed by number and distribution of nucleated micro cavities and by stress internal level present in the material.
Lucio Salgado and Francisco Ambrozio Filho
D. A.P. Reis et al., "Microstructural Evaluation of the Zirconia Plasma Sprayed Coating on Ti-6Al-4V Alloy after Creep Test", Materials Science Forum, Vols. 591-593, pp. 839-844, 2008