This study investigates the co-deposition of aluminum and chromium oxides from solution precursor feedstocks with the aim of maximizing the α-alumina content. A hybrid water-stabilized plasma torch was used to spray the feedstock materials and the deposition principles were studied. The chemical composition of the deposits corresponded to the formulation of the feedstocks, indicating a uniform deposition of both materials. It was found that α-phase content can be increased in the coatings by increasing the Cr-forming precursor in the solution.

The agglomeration process plays an important role in suspension plasma spraying (SPS), affecting the state of particles prior to impact and consequently the mechanical properties of the coated substrate. This paper presents the results of an investigation on the agglomeration of submicron YSZ particles sprayed from a water suspension. The shape and surface morphology of transient and final agglomerate structures was studied by injecting YSZ suspensions with a nebulizer into an inductively coupled plasma torch. It was found that particle agglomeration occurs in successive stages identified as cup or doughnut shaped agglomerates, polycrystalline particles, and amorphous or partially molten particles.

In this work, numerical models are developed and used to simulate magneto-hydrodynamic fields inside a dc plasma torch during suspension plasma spraying and their influence on arc attachment. A Reynolds stress model is used to simulate turbulent plasma flow and a discrete phase model simulates the effects of arc fluctuation on suspension droplets in the plasma jet. Submicron yttria-stabilized zirconia particles, suspended in ethanol, are modeled as multicomponent droplets and the KHRT model is used to simulate their breakup. The results show that particles are significantly affected by plasma arc fluctuations and that fine particles near the centerline of the torch are hotter and experience better penetration into the plasma jet.

This study compares the performance of different measurement methods for characterizing particles during thermal spraying. The accuracy of double-point and single-point measurements is assessed in the context of HVOF and suspension plasma spraying (SPS) where in-flight particle temperature and velocity are recorded for different powders and suspensions. The results are evaluated by analyzing splats and correlating their size and shape to in-flight particle temperature measurements. It is shown that particle diagnostic systems based on single-point measurements are well suited for SPS and HVOF processes.

This study investigates the effect of suspension plasma spraying (SPS) parameters on inner diameter coatings produced from yttria suspensions, one in water and one in ethanol. Thermal spray trials were conducted at different spray distances, transverse speeds, and spray angles, with and without a water shroud. The coatings obtained were then examined in order to assess the influence of each parameter and the effect of water cooling on substrate temperature, porosity, vertical cracking, nodule formation, surface roughness, and deposition rate. Key findings and correlations are presented in the paper along with recommended practices and potential improvement pathways.

Strontium zirconate is a candidate material for thermal barrier coatings due to its high melting point, good sintering resistance, and high TCE. One drawback, however, is a phase transition that occurs below 1200 °C , although rare-earth element doping offers a way to suppress it. In this study, SrZrO 3 doped with two rare earth oxides, ytterbia and gadolinia, is deposited by solution precursor plasma spraying and the layers obtained are evaluated before and after heat treatment. The coatings are characterized by two phases, SrZrO 3 and t-ZrO 2 , with interpass boundary structure, nano and microscale porosity, and through-thickness vertical cracks. XRD analysis after heat treatment at 1400 °C for 360 h shows that the two phases are very stable due to the doping of rare-earth elements, which is also shown to reduce thermal conductivity in the as-sprayed deposits by nearly 35%.