Plasma Spray Synthesis Research Articles

Oxidation Behavior of Titanium Carbonitride Coating Deposited by Atmospheric Plasma Spray Synthesis

As a high-hardness and anti-frictional material, titanium carbonitride (TiCN) thick coatings or thin films are increasingly being used in many industrial fields. In the present study, TiCN coatings were obtained by atmospheric plasma spray synthesis or reactive plasma spray. In order to promote the reaction between the Ti particles and reactive gases, a home-made gas tunnel was mounted on a conventional plasma gun to perform the spray process. The oxidation behavior of the TiCN coatings under different temperatures in static air was carefully investigated. As a result, when the temperature was over 700 °C, the coatings suffered from serious oxidation, and finally they were entirely oxidized to the TiO2 phase at 1100 °C. The principal oxidation mechanism was clarified, indicating that the oxygen can permeate into the defects and react with TiCN at high temperatures. In addition, concerning the use of a TiCN coating in high-temperature conditions, the microhardness of the oxidized coatings at different treatment temperatures was also evaluated.

Plasma-spray synthesis and characterization of ti-based nitride and oxide nanogranules

The synthesis of nanosized Ti-based nanogranules via plasma spraying is reported. The synthesis route involved use of both nitrogen and oxygen gases with varying results. In the case of nitrogen, a mixture of titanium nitrides were produced, yielding both the Ti2N and the sub-stoichiometric TiN0.61 compounds. In the case of oxygen, both the stoichiometric rutile and TiO ceramic phases were indexed. Based on EDS analysis, even fractional oxygen concentrations caused tungsten impurities which originated from the cathode electrode. The method yielded particle mass median sizes of the order of 15nm and the smallest particles detected were 5nm.

Plasma-spraying synthesis of high-performance photocatalytic TiO2 coatings

Anatase (A-) TiO2 is a photocatalytic material that can decompose air-pollutants, acetaldehyde, bacteria, and so on. In this study, three kinds of powder (A-TiO2 without HAp, TiO2 + 10mass%HAp, and TiO2+30mass%HAp, where HAp is hydroxyapatite and PBS is polybutylene succinate) were plasma sprayed on biodegradable PBS substrates. HAp powder was mixed with A-TiO2 powder by spray granulation in order to facilitate adsorption of acetaldehyde and bacteria. The crystal structure was almost completely maintained during the plasma spray process. HAp enhanced the decomposition of acetaldehyde and bacteria by promoting adsorption. A 10mass% HAp content was the most effective for decomposing acetaldehyde when plasma preheating of the PBS was not carried out before the plasma spraying. The plasma preheating of PBS increased the yield rate of the spray process and facilitated the decomposition of acetaldehyde by A-TiO2 coatings without HAp. HAp addition improved photocatalytic sterilization when plasma preheating of the PBS was performed.

Reactive plasma spraying synthesis and characterization of TiB2–TiC–Al2O3/Al composite coatings on a magnesium alloy

In situ TiB2–TiC–Al2O3/Al composite coatings were successfully synthesized on a magnesium alloy substrate by the technique of reactive plasma spraying from an Al–TiO2–B4C system. Phase composition and microstructure of the coatings were characterized by using X-ray diffraction and scanning electron microscopy, respectively. The coatings were subjected to many property tests of bonding strength, micro-hardness, abrasive wear and electrochemical corrosion. The results indicated that regardless of the Al content in the Al–TiO2–B4C system, the desired phases of TiC, TiB2, Al2O3 and/or excess Al were produced in the coatings with no intermediate phases. The coatings exhibited the typical lamellar structure and bonded strongly to the substrate. Micro-hardness and wear resistance of the coatings decreased with the increase of Al content. However, the increase in Al made the coatings have better corrosion resistance because of the denser structure. The coatings by reactive plasma spraying from the Al–TiO2–B4C system could provide a good combination of protection for the magnesium alloy against both wear and corrosion.

Mechanism in reactive plasma spraying synthesis of TiC–TiB2 composite coating

Self-propagating high-temperature synthesis reaction in the LaMgAl11O19–Ti–B4C system was quenched in the glove box and during plasma spraying, respectively, in order to clarify the formation mechanism of in situ TiC–TiB2 composite coating. Microstructure of the quenched samples was investigated by X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectrometer. The results showed that the formation mechanism of TiC and TiB2 during reactive plasma spraying is same as that in the glove box, namely the Ti–B–C melt is first formed by B4C particles dissolving into the Ti–B eutectic liquid as well as the molten Ti, and then TiC and TiB2 are formed and precipitated from the saturated Ti–B–C melt.

Plasma spray synthesis of La10(SiO4)6O3 as a new electrolyte for intermediate temperature solid oxide fuel cells

The apatite-type lanthanum silicate films were successfully synthesized by modified atmosphere plasma spraying using lanthanum oxide and silicon oxide mixed powders and precalcined hypereutectic powders in the size range 1–3μm and 5–8μm, respectively, as starting feedstock materials. The films differed not only in microstructural scale, but also in the characteristic of the degree of film densification. A detail describing the evolution of microstructure has been discussed. A considerable improvement in densification of the La10(SiO4)6O3 electrolyte films has been observed.

Liquid Precursor Plasma Spraying of Functional Materials: A Case Study for Yttrium Aluminum Garnet (YAG)

RF precursor plasma spray synthesis (RFPPS) is an innovative and rapid technique to deposit functional oxide coatings by starting from liquid inorganic precursors and directly producing ceramic coatings. RFPPS offers excellent opportunities in exploring the nonequilibrium phase evolution during plasma spraying of molecularly mixed precursors to form multicomponent oxides. A detailed discussion of progress, critical issues and consideration in precursor development, RF plasma spraying, coating development, and phase evolution of yttrium aluminum garnet (YAG) is presented as a case study. Appropriate selection of precursors and proper tuning of spray parameters resulted in amorphous or crystalline coatings in the as-sprayed condition. YAG phase selection has also been investigated using a discrete, low-density combinatorial synthesis approach.

Titanium carbonitride thick coating prepared by plasma spray synthesis and its tribological properties

TiCN coating, owing to its superior wear-resistance, has been frequently applied in many fields. TiCN thick coating was first prepared by reactive plasma spraying. The phase composition, microstructure and tribological properties of the TiCN coating were investigated in this research. Experimental results show that the microstructure of the TiCN coating was quite dense, and there was also a little amount of titanium oxides within the coating. By XPS analysis, Ti-C and Ti-N bonds were detected in the coating. The TiCN coating exhibited superior wear-resistance. The failure mechanism was attributed to the adhesive wear, the grinding of TiCN hard-grain, as well as the coating failure by oxidation. There were more Fe, Cr, O, etc. in the failure zone, suggesting that the corrosion propagated gradually from surface to interior.

The solution precursor plasma spray processing of nanomaterials

Solution precursor plasma spray (SPPS) synthesis is a simple, single-step, and rapid technique for synthesizing nano-ceramic materials from solution precursors. This innovative method uses molecularly mixed precursors as liquids, avoiding a separate processing method for the preparation of powders and enabling the synthesis of a wide range of metal oxide powders and coatings. Also, this technique is considered to be promising for the formation of non-equilibrium phases in multi-component oxide systems. This short review provides an insight into the important aspects of SPPS, the properties obtained in comparison to conventional plasma spray, and the potential applications of the SPPS process.

Plasma spray synthesis of ultra-fine YSZ powder

A plasma spray process has been developed for the mass production of nanopowders for solid oxide fuel cells (SOFCs) and significant technical developments have been achieved during the past 2 years. Ultra-fine powders of 8 mol% yttria-stabilized zirconia (YSZ) were produced directly from a precursor solution via plasma spray process. The powders were characterized by X-ray diffraction (XRD), nitrogen absorption technique (BET), transmission electron microscopy (TEM), particle size analysis (PSA), and thermogravimetric analyses (TG). The as-sprayed YSZ powders with cubic phase were obtained without obvious impurity species. BET surface area of the sprayed powder reached as high as 27 m 2 g −1, indicating an equivalent particle size of 37 nm. The powder showed mostly spherical with mean size of about 100–200 nm by TEM results. Introduction of an organic additive resulted in a significantly increased specific surface area, accompanied by a slight decrease in grain size. This plasma spray process has the potential to be a less costly and time saving one for nanopowder production than the existing wet chemistry processes.

Plasma Spray Synthesis from Precursors: Progress, Issues, and Considerations

Precursor plasma spray synthesis is an innovative and rapid method for making functional oxide ceramic coatings by starting from solution precursors and directly producing inorganic films. This emerging method utilizes molecularly mixed precursor liquids, which essentially avoids the handling and selection of powders, opening up new avenues for developing compositionally complex functional oxide coatings. Precursor plasma spray also offers excellent opportunities for exploring the nonequilibrium phase evolution during plasma spraying of multicomponent oxides from inorganic precursors. Although there have been efforts in this area since the 1980s and early 1990s with the goal of synthesizing nanoparticles, only recently has the work progressed in the area of functional systems. At the Center for Thermal Spray Research an integrated investigative strategy has been used to explore the benefits and limits of this synthesis strategy. Water- and alcohol-based sol/solution precursors derived from various chemical synthesis methods were used as feedstocks to deposit thin/thick films of spherical and nanostructured coatings of yttrium aluminum garnet (YAG), yttrium iron garnet, lanthanum strontium manganate and Zr-substituted yttrium titanates, and compositions of Y2O3-Al2O3 and their microstructural space centered around stoichiometric YAG. A detailed discussion of the salient features of the radiofrequency induction plasma spraying approach, the results obtained in the investigations to develop various functional oxide coatings, and process issues and challenges are presented.

A Review on the various synthesis routes of TiC reinforced ferrous based composites

The major thrust underlying the processing of Fe-based composites has been directed towards improving the wear resistance of steel or castiron by incorporating some reinforcing phase, e.g., carbides, oxides, etc. The present article provides a review on the various synthesis routes of TiC reinforced Fe-based composites, i.e., powder metallurgy, conventional melting and casting, carbothermic reduction, combustion synthesis, aluminothermic reduction, electron beam radiation, laser surface melting, and plasma spray synthesis, highlighting the advantages and disadvantages associated with the different routes of synthesis.

High pressure reactive plasma spray synthesis of titanium nitride based coatings

The term thermal spray covers a wide range of fabrication methods for surface engineering applications. A very promising thermal spray process involves the production of protective coatings or freestanding components by reactive plasma spray (RPS) techniques. Using reactive gases such as nitrogen or methane it is possible to synthesise hard nitride and carbide phases in reactive metals such as Ti, Cr, and Al. In this investigation RPS was used to produce composite titanium nitride/titanium coatings. Commercially pure titanium powders were used as raw materials and sprayed in a nitrogen atmosphere at up to 300 kPa. The process was carried out by means of a controlled atmosphere plasma spray system, allowing spraying in the pressure range 10–400 kPa. The effects of chamber pressure, plasma gas composition, and spraying distance on the scope of the expected reactions were evaluated. Phase analysis, measurements of nitrogen content and Vickers microhardness, and metallographic investigation of the as sprayed coatings revealed that titanium hard phases were synthesised during spraying and became embedded in the titanium matrix. High pressure significantly enhanced nitride formation (Ti2 N, TiN, TiN1–x ) in the titanium matrix. Microhardness values up to 1433 HV0·3 were obtained, with maximum nitrogen content of about 11·1 wt-%. Studies on sprayed particles showed that TiN was the dominant phase formed during flight, suggesting that diffusion processes play an important role in the substrate. Compared with pure titanium deposits, coatings produced by RPS are much harder and have better tribological properties.

Deposition and Characterization of Y3Al5O12 (YAG) Films and Powders by Plasma Spray Synthesis

ABSTRACTYAG powders and coatings were developed for the first time by a novel precursor plasma spraying technique using the radio frequency (RF) induction plasma technique. The XRD of the as -sprayed coating confirms the presence of YAG, H-YAP or O-YAP or a mixture of the above depending on the spray conditions. 27Al MAS NMR of the YAG coating corroborates the x-ray results. TEM studies on the coatings confirm that the coating consists of nano-structured particles. The successful spraying of these complex oxide coatings proves that chemistry of phase formation can be controlled in the plasma, thus opening up new avenues in material synthesis.

Titanium carbide–iron composite coatings by reactive plasma spraying of ilmenite

Abstract Titanium carbide–iron composite coatings have been developed by reactive plasma spray synthesis using ilmenite ore concentrate as the feedstock powder and methane as the reactive gas. The coatings have been characterized by X-ray diffraction and SEM. The microstructure of the coatings indicate good interparticle cohesion with very little porosity.

Synthesis and Characterization of Grading Profiles in Plasma Sprayed NiCrAlY-Zirconia FGMs

The versatility with respect to feed materials and process conditions makes plasma spray processing a flexible and inherently economic means for producing FGMs. However, successful synthesis of FGMs by plasma spray requires fundamental understanding of the process variables and associated materials response in the plasma flame. A multi-institutional, interdisciplinary effort is currently underway examining the important attributes in the plasma spray synthesis of FGMs. Fundamentals associated with processing, diagnostics and materials properties have been investigated in an integrated manner so as to develop strategies for effective development and utilization of FGMs. In an initial study, multi-particle behavior in plasmas has been investigated. Particle characteristics of the FGM species and their spray behavior within the plasma spray plume have been optimized. Based on these optimization studies composite mixtures of metal and ceramic have been deposited and their deposition characteristics with respect to composition have been assessed. Using these results the process has been controlled to achieve stepped, linear and parabolic grading profiles. The step lengths have been varied in an effort to analyze the physical. thermal and mechanical characteristics of the FGMs. Deviations from targeted compositions have been assessed and related to process conditions and analysis techniques.

Plasma spray synthesis of nanomaterial powders and deposits

Conventional plasma spraying was used to process atomized liquid droplets of precursor solutions to produce alumina, zirconia and yttria stabilized zirconia nanoparticles and deposits. An electrostatic precipitator collected the plasma synthesized ceramic particles at a rate of ~0.2 mg s −1, with ~5–20% collection efficiency. Spray processing produced 1–50 nm size ceramic particles. The size, shape and phase composition of the nanomaterials depend on the spray feedstock. Organo-metallic precursors gave rise to a narrow range of fine-grained material, while aqueous solutions produced wider distributions of larger size grains. Spray processing of liquid feedstock produced nanodeposits with a powdery morphology. Plasma spraying of liquid precursors is a viable technique to produce nanoparticles and deposits.

Plasma spray synthesis of composite materials with fine titanium carbide particles

Composite materials containing fine titanium carbide particles are produced through reaction synthesis by plasma spraying an agglomerated composite powder, consisting of elemental titanium and graphite. Particles of titanium carbide are bonded with the titanium phase in the sprayed deposit. There are typically two types of titanium carbide particles, one with a diameter of 1–2 μm and the other 0.1–0.2 μm. The effect of the plasma spray conditions on the amount of titanium carbide in the deposits and the formation of the microstructures are discussed.

The influence of composition and process parameters on the microstructure of TiC-Fe multiphase and multilayer coatings

Abstract Composite TiC-Fe coatings obtained by the plasma spray synthesis process can be composed of alternate TiC-rich and TiC-poor lamellae of different hardnesses. This study was undertaken to assess the influence of the fabrication parameters on the microstructure of these coatings. Both the composition of the micropellets, which lead to the synthesis and dispersion of fine crystals within the iron matrix upon spraying, and the spraying parameters were examined. Among all the variables considered it was found that the parameters related to the fabrication of micropellets, such as their size and their expected TiC volume content, and those related to the solidification of synthesized products are the main factors affecting the hardness of TiC-rich layers. Coatings obtained by spraying micropellets comprising TiC and iron powders agglomerated together are composed of large angular and hard TiC particles embedded in a matrix whose hardness is between 300 and 500 kgf mm-2. In contrast, plasma-spray-synthesized coatings are composed of alternate soft and hard layers whose hardness varies according to the fabrication parameters and is between 1000 and 1800 kgf mm-2 for hard layers and between 300 and 600 kgf mm-2 for soft ones. These plasma-spray-synthesized TiC-Fe coatings, because of their multilayer and fine-grained multiphase microstructure, are expected to be more resistant to crack propagation and, consequently, to wear.

Synthesis and deposition of TiB2-containing materials by arc spraying

Abstract Wear-resistant coatings containing TiB 2 have been previously synthesized and deposited using the plasma spray synthesis process. The technique consists of plasma spraying micropellets comprising the reagents (ferrotitanium and boron or ferroboron) and depositing the as-reacted products on a substrate. In order to facilitate the deposition of the materials, to lower the cost and to increase the spray rate, a different approach has been tried. It consists of depositing TiB 2 -containing material by using the flexible arc-spraying technology. Coatings containing TiB 2 have been synthesized and deposited by arc spraying core wires containing the reagents mentioned above. Even though the process appears simpler, it was found that the wire fabrication as well as its deposition must be carefully controlled in order to obtain the desired coatings.