Suspension Plasma Spray: industrial developments and characterizations for gas turbine components
The nanometer size of the powders used in SPS leads to a set of microstructures of interest to several applications. An industrial set-up has been characterized in terms of reliability of the deposition technique, while providing an in-depth investigation of the role of critical parameters, such as the standoff distance and torch movement speed, on the coating characteristics and, in turn, performance. Different columnar microstructures were produced using an YSZ ethanol-based suspension and then characterized by means of microstructural investigation, x-ray diffraction, bond strength, thermal cycling tests and jet erosion resistance up to 900 °C.
This investigation shows a full comparison of new SPS TBCs with the well-known porous and vertically segmented TBCs in terms of coating performance and industrial feasibility. It was particularly found that, when columns consist of fine, well-flattened and tightly adherent splats, SPS TBCs exhibit better thermal cycling and erosion resistance than APS ones, which undergo extensive interlamellar delamination.
Moreover this SPS-based coating has been applied on a real gas-turbine blade and the microstructure has been evaluated to assess the process feasibility.