Plasma sprayed erbia stabilized zirconia coatings

The stabilization of the phases in zirconia alloys is pivotal in their applications as advanced structural ceramics. Stress-induced transformation toughening is dependent on the characteristics of the metastable tetragonal zirconia phase. Rare earth oxides are known to stabilize the cubic and tetragonal phases. This paper presents the preparation of erbia-stabilized zirconia coatings by plasma spraying. Amount of erbia ranged from 2 mol% to 8 mol%. The feedstock is prepared by a combination of mechanical milling and thermal plasma melt and solidification processes. Phase analysis of the rapid solidified powders and plasma sprayed coatings are determined through X-ray diffraction (XRD). Results show that the tetragonal phase is stabilized when 2 to 4 mol% erbia are added. However, at 6 mol% and 8 mol% erbia the cubic phase is stabilized. Heat treatment at high temperature (1400°C) showed that there could be some amounts of the nontransformable t' phase. The amount of monoclinic phase in the coatings is lower than the feedstock powder suggesting that further stabilization is possible with the plasma spray deposition.