Most of ductile metals can be deposited by cold spray (CS). For brittle ceramic, such solid-state deposition process is still questionable, but some recent work on Ti0 2 or hydroxyapatite powders have shown that micrometric ceramic powder could be deposited by CS. In this work, it is claimed that the nature and the porous architecture of a ceramic powder with agglomerated ultra-fine grains play an important role on the impact behaviour. The aim of this work is to investigate the deformation behaviour of ceramic agglomerated powders under high velocity impact. Two different powders, respectively 3YSZ and Y 2 O 3 , were selected in order to study their architectures (particle size, porosity, density, crystallite size, etc.). Cold spray “splats” experiments, with various spraying distances to vary the particles velocities upon impact, were carried out to observe the deformation and fragmentation. In case of Y 2 O 3 , cold spray with dynamic vacuum surrounding atmosphere up to 3kPa were also prepared to evaluate the role of the atmosphere on the resulting impact. In parallel, in situ SEM micro-compression tests at 10 −2 s −1 on cross-sectioned 3YSZ particles involving flat-punch nano-indentation and micropillar compression were performed. By modelling the compression tests, the aim is to identify a Drücker-Prager behaviour law suitable for an agglomerated ceramic powder under quasi-static compression. Such deformation behaviour could help to better understand the compaction behaviour of agglomerated powders.

In the semiconductor industry, plasma etching processes are widely used. Process chamber parts that are located in the plasma etching system are also exposed to the harsh environmental conditions. Thus, parts located close to the process area are typically coated with yttria to increase service life, and thus process performance. However, such yttria coatings are usually porous, and thus can be attacked by fluorine containing plasma. In order to increase the lifetime of the components in the plasma etching system, this research project aimed to improve the protective yttria layer by reducing the porosity of the protective layer. Specifically, a design of experiment was employed in which the porosity was the target value. The main effects of the coating parameters and their interactions including the surface treatment before the coating process were determined. Furthermore, the bonding of the protective coating to the component to be protected, as well as the element distribution and the coating morphology were investigated. The results and their ramifications with respect to the envisaged application will be discussed.

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.

This study compares the performance of an ordinary plasma spray gun with that of recently developed gun designed for spraying feedstock suspensions on inner diameter surfaces. To evaluate the guns, yttrium oxide was deposited on 304 stainless steel while varying supply pressure, spraying distance, and gun traverse speed. Different methods of delivering suspension spray material to the gun were also investigated. Although Y 2 O 3 inner-diameter coatings were successfully formed, hardness and cross-sectional porosity need improvement. Based on the findings, it may be necessary to increase substrate temperature, readjust spraying parameters, and optimize feedstock materials.

This study assesses the plasma erosion resistance of Y 2 O 3 and YF 3 films deposited on aluminum 6061 substrates by vacuum kinetic spraying, a low-temperature deposition process. Y 2 O 3 and YF 3 powders with different particle sizes were selected as feedstock materials and characterized in their as-delivered and heat-treated states. Dense films several micrometers in thickness were sprayed using helium as the process gas and surface component analysis confirmed the successful formation of the yttrium-based layers. Plasma etch rates were measured in nanometers per minute and the results show that there is no significant difference between the two films.

As a candidate material against plasma etching, yttrium oxide has been coated onto etching chamber by plasma spray technique. However, the plasma spray technique introduces undesirable coating properties such as porous structure and deleterious thermal effects. To reduce the disadvantage of thermal impact, cold spray was used as an alternative technology to deposit thick and dense yttrium oxide coatings. Primary nanoscale Y 2 O 3 were used as the original powder, for the ceramic materials are intrinsic brittle and are difficult to be deposited by cold spray. The nano-powder were first agglomerated by hydrothermal treatment with addition of inorganic salt to acquire suitable powder for cold spray, and then deposited on aluminum alloy 6061 substrates by cold spray process with compressed air as propellant gas. About 200μm yttrium oxide coatings were formed on the substrate alloy. Different processing parameters were employed to optimize microstructure and properties of the coating.

This study investigates the heat-shock properties of metal-oxide films synthesized from ethylenediamine tetraacetic acid (EDTA) complexes using conventional flame-spray equipment. An EDTA·Y·H powder was placed in the feed unit of the sprayer and transported by a flow of oxygen to the gun. The powder was sprayed using a mixture of H 2 and O 2 as the flame gas, producing a layer of yttrium oxide on a stainless steel substrate. XRD analysis was used to examine the crystal structure of the deposits and SEM imaging revealed the surface and cross-sectional microstructure. A cyclic thermal shock test was conducted and the deposited film was analyzed for the existence of cracks, deformation, and delamination. Although the number of cracks, crack lengths, and cracks per unit area increased due to heat shock, delaminations were not observed. The results show that the Y 2 O 3 films have high thermal-shock resistance and are suitable for use as thermal barrier coatings.

This study investigates the influence of particle size, nozzle diameter, gas flow rate, and stand-off distance on the microstructure and density of suspension plasma sprayed yttrium-oxide coatings and the intermediate effect of particle characteristics. Three ethanol suspensions were prepared, one with coarse Y 2 O 3 , one with fine Y 2 O 3 , and one with submicron YSZ. The suspensions were injected vertically into the plasma jet downstream of the nozzle and a thermal spray sensor was used to measure in-flight velocity and temperature. The coatings were found to have columnar and dense vertically cracked (DVC) microstructure, varying in hardness and density. Text results and examination findings are presented and correlated with spray parameters, particle properties, and possible coating formation mechanisms.

In the present study, Al 2 O 3 and Al 2 O 3 -Y 2 O 3 composite coatings were deposited by atmospheric plasma spraying and compared based on microstructure, hardness, and sliding wear behavior. The mass ratio of α-Al 2 O 3 /γ-Al 2 O 3 was found to be 0.53 in the composite, compared to 0.08 in the alumina layer, which explains why the Al 2 O 3 -Y 2 O 3 coatings are harder and better conductors of heat. Tribological tests show that the friction coefficients of the composite coating samples are more stable and the wear rates lower, which may be related to the formation of a graphite transferred film on abraded surfaces.

In this study, yttria films with high thermal shock resistance were synthesized from a metal-EDTA complex by means of combustion flame spraying. A rotating stage and various cooling agents were used to control substrate temperature during deposition. Although thermally extreme environments were employed during synthesis, the obtained films showed only a few cracks and some minor peeling in their microstructures. In the case of a Y 2 O 3 film synthesized using substrate rotation and water atomization, the porosity was found to be 22.8% and the temperature of the film immediately after deposition was 453 °C, owing to a high heat of evaporation in the cooling water.

This study investigates the feasibility of spraying aluminum nitride-alumina-yttria mixtures in a nitrogen plasma ambient. Coatings consisting of h-AlN, c-AlN, Al 5 O 6 N, and γ-Al 2 O 3 with small amounts of α-Al 2 O 3 and aluminum-yttrium oxide phases were produced. Although using the Y 2 O 3 additives significantly affected the process and microstructure, it did not achieve the high thermal conductivity desired in as-sprayed coatings. However, a high thermal conductivity (>90 W/m·K) AlN coating was fabricated by increasing the AlN content and enhancing sintering during heat treatment.

The aim of this study is to improve the releasability of carbon fiber reinforced plastic (C-FRP) molds by depositing a plasma-sprayed Y 2 O 3 coating on working surfaces. Composite molds are considered for use in IC encapsulation. To promote adhesion, an interlayer, either copper or gradient yttria, is applied between the substrate and coating. The coatings deposited over gradient Y 2 O 3 performed better than coatings applied over copper due to the large reduction in thermal mismatch achieved with a graded thermal expansion coefficient. Preliminary releasability results show that the yttria coatings have high adhesion strength and the potential to uniformly reduce release forces between C-FRP surfaces and epoxy resins.

This study investigates the phase stability and thermophysical properties of Y 2 O 3 and Yb 2 O 3 co-doped SrHfO 3 (SHYY) powder and bulk material along with the phase stability and microstructure evolution of as-sprayed SHYY coatings during annealing. The powder was synthesized by a solid-state reaction at 1450 °C, showing good phase stability up to 1400 °C. Dilatometry measurements revealed no abnormal changes in the coefficient of thermal expansion over a temperature range of 200-1300 °C. The thermal conductivity of the bulk material was found to be 16% lower than that of SrHfO 3 . Free-standing SHYY coatings deposited by air plasma spraying were also tested. The coatings consisted of SHYY and a minor amount of secondary phase Yb 2 O 3 and exhibited good phase stability during heat treatment at 1400 °C for 288 h. Coating samples examined after 216 h still exhibited a columnar microstructure.

This study compares the morphology, porosity, and purity of yttria powders produced by spray drying, spray drying and sintering (SDS), and spray drying and plasma fusion (SDPF). The surface morphology of each type of powder is examined by SEM. Pore volume and density are determined by Hg porosimetry, and impurity concentrations are assessed via glow discharge mass spectrometry (GDMS). Coatings made from the powders by means of air plasma spraying are evaluated based on porosity, spray time, powder consumption, and embedded fine particles.

This study investigates plasma erosion mechanisms in alumina and yttria coatings produced by air plasma spraying. Plasma exposure tests were conducted in ICP etchers using CF 4 , Ar, and O 2 as process gases. Etching rates were calculated based on height differences between masked and unmasked areas and coating cross-sections, surface morphologies, and phase distributions were analyzed. In the Al 2 O 3 layers, erosion increased with increasing CF 4 concentration and fluoridation of the coating surface was confirmed, suggesting that chemical erosion is the dominant mechanism. Although fluoridation occurred on Y 2 O 3 surfaces as well, the amount of erosion in CF 4 was the same as in the Ar environment. It is thus assumed that the fluoride formed on Y 2 O 3 surfaces is very stable and that physical erosion due to ion sputtering is the dominant mechanism.

In this study, dense yttria coatings are produced by conventional flame spraying using a yttrium ethylene diamine tetra acetic acid (Y-EDTA) complex as the feedstock powder. By adjusting spray parameters, the organic components in the EDTA are completely decomposed and only crystalline Y 2 O 3 phases are found in the deposits. Compared to atmospheric plasma sprayed Y 2 O 3 , Y-EDTA coatings produced by reactive flame spraying have better surface morphologies with fewer microcracks and are obtained at lower cost.

Yttrium oxide (Y 2 O 3 ) can be used in different applications such as corrosion resistance, high temperature applications and semi-conductor production equipment due to its very high thermal and chemical stability. In the current research, yttria coatings were processed using a new type of DC plasma gun consisted of molecular gases CO 2 +CH 4 . Physical and structural properties were compared with the coating made by SG-100 plasma torch. Gas mixture of CO 2 +CH 4 improves the torch efficiency due to its high thermal enthalpy and conductivity which leads to increased particle temperature and complete fusion of the sprayed particles during the process of coating. SEM study of the structure revealed that the coating has higher density and lower porosity compared to the coating produced by SG-100 torch. No unmelted particles can be observed in the coating. XRD analysis of the coating showed that the coating contains no amount of harmful metastable monoclinic phases. This all proves the better quality of the coatings deposited by CO 2 +CH 4 gas mixture in comparison to the conventional coatings.

Agglomerate sintered and blended NiCrAlY-Y 2 O 3 cermets were prepared from NiCrAlY and Y 2 O 3 powders by two process routes. The particle morphologies and powder characteristics of both cermets feedstock using for thermal spraying were investigated. Both types of NiCrAlY-Y 2 O 3 cermets and one commercial CoCrAlY-Y 2 O 3 cermets were HVOF thermal sprayed onto the stainless steel substrate to obtain coatings having a thickness about 100 microns. Porosity and thermal shock resistance of coatings were examined. Four thermal sprayed coatings were comparatively evaluated build-up resistance by contacting reaction with MnO, Fe 3 O 4 powders and manganese bearing carbon steel statically at high temperatures. The agglomerate sintered NiCrAlY-Y 2 O 3 coatings have good resistance to manganese oxide build-up but bad resistance to iron oxide build-up. The agglomerate sintered cermets coating has better build-up resistance than blended cermets coating.

Oxidation behavior of NiCrAlY powder, blended with nano and micro sized Al 2 O 3 and Y 2 O 3 was studied to understand the effect of nano/micro oxide powder dispersion. The blended powders were applied on the IN 718 substrates by HVOF technique. The present work compares the oxidation behavior of IN 718 superalloy, coated with NiCrAlY powders, dispersed with nano and micro Y 2 O 3 , Al 2 O 3 oxide. Coated samples were characterized by XRD, SEM/EDAX in terms of surface composition, scale cross section and the identification of different phases. The oxidation tests were carried out at 1223K, 1323K, 1423K in air. Oxidation kinetics infer that at 1223 K and 1323 K, nano yittria addition, in fact, resulted in higher oxidation rate, while nano alumina addition resulted in lower oxidation rate. The effect was more pronounced at 1423 K, where the nano and micro size alumina, yttria addition, resulted in bringing down the oxidation rate considerably.

Very low pressure plasma spraying has been intensively studied in recent years especially the properties of plasma jet. These properties are affected by plasma generating and working conditions. These operating parameters such as arc power, plasma gas flow rate and chamber pressure have influences on specific enthalpy and temperature of plasma jet. In this work, the measurements under very low pressure were performed using enthalpy probe which was previously modified (increase of the internal diameter and depositing TBC coating (Ni/Al and ZrO 2 + Y 2 O 3 ) on the head). Different parameters, for instance, current intensity, hydrogen gas flow rate and detecting distance were changed in order to point out their effect on the characteristics of plasma jet. The specific enthalpy, temperature and quantity of heat in this situation were obtained.