Abstract This study investigates the microstructure and hardness of coatings produced by atmospheric plasma spraying using a commercial (Al,Cr) 2 O 3 solid solution (ss) powder blended with various amounts of TiO 2 . The microstructures were analyzed using SEM, EDS, and XRD measurements. It was shown that blending with TiO 2 reduces porosity and defect density while increasing deposition efficiency and microhardness. Small amounts of Ti in ss (Al,Cr) 2 O 3 splats were detected in coatings prepared from blends with higher TiO 2 content. Variations in aluminum and chromium content were also observed.

Abstract Boundary layers on surfaces will change from laminar to turbulent flow after a critical length. Due to the differing heat transfer coefficients of laminar and turbulent flow, the point of transition can be detected by heating the surface and measuring surface temperature by thermographic imaging. Locating the transition point is crucial for the aerodynamic optimization of components. In this study, fiber reinforced polymer composites (FRPCs) were chosen as the test substrate. Experiments were conducted using the flame spray process and NiCrAlY coatings. Multilayered coatings consisting of an aluminum bond coat, a layer of alumina as electrical insulation, and a heating layer of titania were fabricated by atmospheric plasma spraying. Free-flight tests were conducted with a functionalized winglet in order to assess the ability of thermally-sprayed heating elements to detect the location of transition of the flow regime. The results showed that the thermally-sprayed elements heat surfaces uniformly, with sufficient radiation losses for thermographic imaging. It was also shown that the change in temperature at the point of transition was readily observable using thermography.