Physicochemical Properties of Yttria-Stabilized-Zirconia In-Flight Particles during Supersonic Atmospheric Plasma Spray

Abstract

In order to achieve better knowledge of the thermal barrier coatings (TBCs) by supersonic atmospheric plasma spraying (SAPS) process, an experimental study was carried out to elaborate the physicochemical properties of particles in-flight during the SAPS process. One type of commercially available agglomerated and sintered yttria-stabilized-zirconia (YSZ) powder was injected into the SAPS plasma jet and collected by the shock chilling method. The YSZ particles’ in-flight physicochemical properties during the SAPS process, including melting state, morphology, microstructure, particle size distribution, element composition changes, and phase transformation, have been systematically analyzed. The melting state, morphology, and microstructure of the collected particles were determined by scanning electron microscopy (SEM). The particle size distribution was measured by a laser diffraction particle size analyzer (LDPSA). Element compositions were quantitatively analyzed by an electron probe X-ray microanalyzer (EPMA). Additionally, the X-ray diffraction (XRD) method was used to analyze the phase transformation. The results showed that the original YSZ powder injected into the SAPS plasma jet was quickly heated and melted from the outer layer companied with breakup and collision-coalescence. The outer layer of the collected particles containing roughly hexagonal shaped grains exhibited a surface texture with high sphericity and the inside was dense with a hollow structure. The median particle size had decreased from 45.65 to 42.04 μm. In addition to this, phase transformation took place, and the content of the zirconium (Zr) and yttrium (Y) elements had decreased with the evaporation of ZrO2 and Y2O3.

Polyetheretherketone and Its Composites for Bone Replacement and Regeneration

“…Porous features offer a remarkable osteogenic response at the cell level, thereby facilitating bone ingrowth of spinal fixation devices. However, the presence of pores throughout entire PEEK implants would degrade the mechanical strength greatly [106]. In this respect, Torstrick et al have introduced a porous surface layer of few micrometers thick with high interconnectivity on PEEK using a melt extrusion and porogen (NaCl) leaching process.…”

“…The technique involves the use of an arc inside the plasma gun to melt ceramic or metal powders at high temperatures. The molten droplets are then propelled onto the target substrate, followed by flattening, rapid solidification, and cooling to form a porous coating layer (Figure 4) [106]. The spraying process can be performed in a vacuum chamber instead of air at atmospheric pressure to prevent the oxidation of the coating material, which is referred to as 'vacuum plasma spraying'.…”

Experimental and Simulation Analysis of the Evolution of Residual Stress Due to Expansion via CMAS Infiltration in Thermal Barrier Coatings

“…During heating, the buckle height is maintained at zero because The manner in which the two major expansion factors affect the buckle height is interesting. Figure 6 shows the buckle height of YSZ induced by CMAS infiltration with different expansion rates where the holding time is 12 h and pre-factor A is assumed to be 0.0014 in Equation (6). In this case, a thermal cycle, including heating, holding, and cooling process, is determined.…”

“…During the cooling stage, the phase transformation plays a crucial role in the thermomechanical failure induced via CMAS infiltration in 7YSZ TBCs. The experimental results indicated [6] that YSZ lacks Y 3+ cations. This can lead to tetragonal-monoclinic transformation at the approximate range of 300-900 • C. This is dependent on the amount of yttrium oxide remaining in zirconia.…”

“…The thermochemical and mechanical reaction of CMAS can dramatically promote the destabilization of YSZ [5]. Phase transformation would occur, and the content of the zirconium and yttrium elements decreases with the evaporation of ZrO 2 and Y 2 O 3 during the supersonic atmospheric plasma spraying process [6]. The original YSZ is composed of 8 wt.% of Y 2 O 3 as a phase stabilizer, and the effects of thermal exposure due to volcanic ash were examined on the original YSZ.…”