Study of nanocomposite hafnia and zirconia based layers produced by plasma spraying

Nanostructured and nanocomposite layers NiCoCrAlY+ ZrO2-7%Y2O3, ZrO2-7% Y2O3+HfO2-9%Y2O3, HfO2-9%Y2O3 with thickness of ∽ 20 μm were formed by low pressure plasma spraying. The structure and composition of the layers have been studied using a scanning electron microscopy, X-ray microanalysis, and XRD analysis. Thermal stability of the coatings has been analyzed using synchronous thermal analysis at temperatures up to 1600 °C. The results of structure and composition analysis of ZrO2-7%Y2O3+HfO2-9%Y2O3 layer suggest the formation ofnanocomposite co-doped regions of the ZrO2-HfO2-Y2O3 solid solution. The layer has greater thermal stability at temperatures up to 1600 ° C and a smaller subgrain size (∽ 33 nm) than for the ZrO2-7% Y2O3 and HfO2-9%Y2O3 layers.

Microstructure and Ablation Behavior of Very Low-Pressure Plasma Sprayed ZrB2-Based Coatings

The effect of deposition pressure on the microstructure and ablation behavior of ZrB2 coatings deposited by very low pressure plasma spraying is investigated. The results show that under a chamber pressure less than 50 kPa, as the spray chamber pressure decreases, the porosity of the coating deposited at the same distance decreases, and the coating prepared under 100 Pa presents the lowest porosity of 1.79 %. Furthermore, among the ZrB2 coatings deposited at 100 Pa, 5 kPa, 10 kPa and 50 kPa, the dense coating deposited at 100 Pa showed the lowest ablation rate of 0.33 μm/s, 0.75±0.08 mg/s.

The Coatings Formation and Characteristic of a Low Pressure Thermal Plasma Torch

Compared with the atmosphere plasma spraying (APS), low pressure plasma spraying (LPPS) has been widely used due to deposit a specific and unique coating. A new low pressure thermal spraying plasma torch was designed according to the plasma spray characteristic in the low pressure environment. The plasma jet characteristic and the coatings microstructure were analyzed. In this study, Kundsen number has a great effect on the heat transfer of feedstock powder. With the increase of current, the plasma torch efficiency will decrease. A equiaxed microstructure of 316L coatings were deposited.