50 vol. % La 2 Ce 2 O 7 (LC)/yttria partially stabilized zirconia (YSZ) composite thermal barrier coating (TBC) was deposited by supersonic atmospheric plasma spraying (SAPS). The mixture of LC and YSZ can effectively eliminate the sudden decrease of thermal expansions coefficients of LC. The results of CMAS corrosion tests indicated that the LC/YSZ composite coating reveals high resistance to the penetration of CMAS with reprecipitation of La-Ce apatite, CaAl 2 Si 2 O 8 , MgAl 2 O 4 and t-ZrO 2 . Furthermore, compared to YSZ coating, the LC/YSZ composite coating can obviously improve the thermal cycling lives under CMAS corrosion.

The present study aims to elaborate the particle in-flight behavior during plasma spraying and its significance in determining the microstructure and mechanical properties of plasma sprayed yttria partially stabilized zirconia (YPSZ) based thermal barrier coatings (TBCs). The as-sprayed YPSZ coatings were characterized in terms of the defects (such as porosity, unmelted particles, cracks and micro-cracks), hardness, elastic modulus and fracture toughness. The results showed that the total defects percentage, porosity, unmelted particles and crack content were found to decrease significantly with the improvement of temperature of in-flight particles. The mechanical properties were associated with the microstructure of these coatings, such as total defects, porosity, unmelted particles and cracks. It was confirmed that the mechanical properties, including hardness, elastic modulus and fracture toughness, notably enhanced with the total defects, porosity, unmelted particles and cracks decreased. The SAPS (supersonic atmospheric plasma spraying) coatings sprayed at 3401 } 3.76 °C and 482 ± 2.18 m/s and a spraying distance of 100 mm possessed the lowest microstructural defects percentage and the most favorable mechanical properties among the 15 coatings.

The powder of HSS (HSS23, AISI M3:2) was deposited by pulsed-PTA method on to low alloyed steel substrate. The influence of pulsation frequency was evaluated on the surface of deposits and on their cross sections by both light microscope and by Vickers hardness measurement apparatus and extreme properties mapping (XPS). Surfacing parameters at current frequency from 0 to 200Hz were tested during deposition of single weld bead. Dilution and heat affected zone were evaluated and compared for all tested parameters. The presence of retained austenite after deposition was determined by X-ray diffraction. The beads deposited with different frequencies differ in their shape, dilution degree, microhardness and penetration depth. It was found that the microhardness increases with current frequency.

In this work, liquid plasma spraying is used to deposit composite coatings for potential use as cathodes in intermediate-temperature solid oxide fuel cells. A suspension containing well-distributed Gd-doped ceria (GDC) nanoparticles in a lanthanum strontium cobalt ferrite precursor solution was used as the feedstock, and GDC concentration was varied to study its effect on phase composition, microstructure, surface morphology, and electrochemical performance. The results are presented and discussed.

In this study, cold sprayed Cu approximately 40 to 60 μm in thickness is deposited on 6063 and LD10 aluminum plate to improve wettability for low temperature soldering and to serve as a barrier layer to protect the substrate from gallium diffusion originating in the solder paste. The effect of the coating on wettability, diffusion, solder joint interface microstructure, and shear strength is investigated in detail.

In the current work, yttria stabilized zirconia splats and coatings were deposited onto superalloy substrates at different temperatures using axial suspension plasma spraying (ASPS). The splats were characterized by scanning and transmission electron microscopy. As the substrates were heated from room temperature to 300 °C, splat morphology changed rapidly. Examination of the morphological and crystallographic features of splats revealed that cooling rate during impacting and spreading might be lower than that of splats deposited by conventional atmospheric plasma spraying. Based on these observations, a possible mechanism is proposed to explain the cauliflower microstructure.

Lanthanum-doped strontium titanate (LST) and samarium-doped ceria (SDC) are promising materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). In this study, LST-SDC composite anodes are produced by suspension plasma spraying and the effects of annealing are assessed. XRD results show that the coatings and powders have the same phase structure. The coatings have a fine porous structure which is beneficial for gas permeability and long three-phase boundaries that facilitate anode reactions. A single cell based on the LST-SDC composite anode was found to perform well at 650-800°C. The results show that annealing improves interface bonding between particles in the anode and at the interface between the anode and electrolyte.

Nanostructured YSZ is expected to exhibit a high strain tolerability due to its low Young’s modulus and consequently high durability. In this study, a porous YSZ as the thermal barrier coating was deposited by plasma spraying using an agglomerated nanostructured YSZ powder on a Ni-based superalloy Inconel 738 substrate with a cold-sprayed nanostructured NiCrAlY as the bond coat. The heat treatment in Ar atmosphere was applied to the cold-sprayed bond coat before deposition of YSZ. The isothermal oxidation and thermal cycling tests were applied to examine failure modes of plasma-sprayed nanostructured YSZ. The results showed that YSZ coating was deposited by partially melted YSZ particles. The nonmelted fraction of spray particles retains the porous nanostructure of the starting powder into the deposit. YSZ coating exhibits a bimodal microstructure consisting of nanosized particles retained from the powder and micro-columnar grains formed through the solidification of the melted fraction in spray particles. The oxidation of the bond coat occurs during the heat treatment in Ar atmosphere. The uniform oxide at the interface between the bond coat and YSZ can be formed during isothermal test. The cracks were observed at the interface between TGO/BC or TGO/YSZ after thermal cyclic test. However, the failure of TBCs mainly occurred through spalling of YSZ within YSZ coating. The failure characteristics of plasma-sprayed nanostructured YSZ are discussed based on the coating microstructure and formation of TGO on the bond coat surface.

There have been recent efforts to expand the thermal spraying capabilities for novel corrosion resistant coatings for metal bipolar plates were produced by thermal spraying for proton exchange membrane (PEM) fuel cell applications. Recently, substrate heated by plasma gun or by external laser beam has been proposed to enhance the mechanical and thermal properties of the coatings. Studies were found that with sufficient substrate heating, substrate melting may happen. When droplets solidified on a thin liquid layer on the top of the substrate, conditions will be similar to crystal growth and Epitaxy film growth will be possible. It is therefore possible that using substrate melting as tool to promote epi-layer growth using plasma spraying. Difficulty is how to control the substrate temperature to cause substrate melting during droplet solidification. In this study we will propose a new idea for better temperature control on the substrate. The capability of epitaxy growth using thermal spraying will be investigated. Molybdenum droplets impact on an Aluminum substrate will be studied. A splat formation model including undercooling, nucleation, and non-equilibrium solidification will be used to study the possibility of the substrate melting and grain size distribution.

Wear of plasma sprayed Cr 2 O 3 TiO 2 , Cr 3 C 2 -NiCr and WC-Co coatings have been evaluated with a block-on-ring arrangement under dry and lubricated conditions. The results indicated that the wear of the coatings was interpreted in term of subsurface grain fracture which was related to the special microstructure of the coatings such as size, shape and distribution of pore as well as crack. Among the four kinds of coating, Cr 2 O 3 coating possesses the lowest wear coefficient. Water accelerated cracking and fracturing and deteriorated the wear resistance of both Cr 3 C 2 -NiCr and TiO 2 coatings. Ethanol reduced the wear of Cr 3 C 2 -NiCr coating, which was attributed to the formation of a smooth surface film mainly consisting of Cr 2 O 3 . Wear of Cr 2 O 3 , coating against an Al 2 O 3 ball at high temperature has been also produced. The wear of Cr 2 O 3 coating against Al 2 O 3 ceramics decreased with increase in temperature and load. The reaction between Cr 2 O 3 coating and Al 2 O 3 , ceramics at high temperature and the formation of a protective film consisting of Cr 2 O 3 , Al 2 O 3 and SiO2 glass on the surface of Cr 2 O 3 coating improved the wear resistance of Cr 2 O 3 coating.