Search

Rare earth ytterbium monosilicate (Yb 2 SiO 5) is one of the most ideal candidates for environmental barrier coatings. In this paper, Yb 2 SiO 5 coating was successfully fabricated by atmospheric plasma spraying technology. The effect of main gas flow rate and spraying powder composition on the microstructure and phase composition of Yb 2 SiO 5 coating were systematically investigated to solve the volatilization of SiO 2 during plasma-spraying process. The results showed that Yb 2 SiO 5 coating was relatively dense with the less internal defects under the main gas flow rate of 35 L/min, and the main gas flow rate from 30 L/min to 40 L/min had no significant effect on the melting effect of spraying powder and the porosity of coating. Yb 2 SiO 5 coating was composed of Yb 2 O 3 , Yb 2 SiO 5 two crystal phases and amorphous phase. The phase composition of coating was not affected by the change of main gas flow rate. After heat-treatment at 1400 °C for 20 h, Yb 2 SiO 5 crystal phase precipitated from the coating, and the content of Yb 2 SiO 5 phase reached 74.29 mol%, and the remaining phase was Yb 2 O 3 phase. The Yb 2 SiO 5 -25.71 mol% SiO 2 coating was still dense, the content of Yb 2 SiO 5 crystal phase was up to 97.76 mol% after heat-treatment, and the content of Yb 2 Si 2 O 7 phase was only 2.24 mol%, indicating that excessive addition of a certain amount of SiO 2 could compensate for the volatilization of SiO 2 , so as to prepare Yb 2 SiO 5 coating with approximate stoichiometric ratio. [ABSTRACT FROM AUTHOR]

Zircon (ZrSiO 4) is an inexpensive and widely available material with excellent thermal properties that makes it an ideal candidate for thermal barrier coatings. Previous works have demonstrated the feasibility of obtaining coatings with a high retention of zircon by plasma spraying of ZrSiO 4 and ZrSiO 4 /ZrO 2 suspensions. Suspensions of ZrSiO 4 /Al 2 O 3 and ZrSiO 4 /TiO 2 were produced by dispersing a micrometric zircon powder into alumina and titania colloidal sols, optimising their colloidal stability and rheological behaviour. Optimised slurries were plasma sprayed onto metallic substrates, obtaining coatings with the typical morphologies obtained by suspension plasma spraying (SPS). Nanostructured coatings with nanoparticles embedded in the molten matrix were obtained at higher proportions of sprayed colloidal sol. The high retention of ZrSiO 4 in the final coatings and the formation of new crystallographic phases of mullite and zirconium titanate by reaction of the by-products of zircon decomposition (SiO 2 and ZrO 2) and the Al 2 O 3 and TiO 2 colloids was demonstrated. [ABSTRACT FROM AUTHOR]

Multicomponent solid solution ceramics have attracted extensive attention for their superior ablation resistance and high-temperature resistance, which are expected to extend the service life of carbon/carbon (C/C) composites under an ablation environment above 2000 °C. Herein, we synthesized (Hf ⅓ Zr ⅓ Ta ⅓)C solid solution ceramic powders via carbothermal reduction. Then a dense (Hf ⅓ Zr ⅓ Ta ⅓)C solid solution ceramic coating was deposited on SiC-coated C/C composites by supersonic atmospheric plasma spraying. The coated samples exhibited a low linear ablation rate of −0.61 μm/s after ablation for 120 s, mainly associated with the formation of a compact oxide scale consisting of (Hf, Zr) 6 Ta 2 O 17 and (Hf, Zr)O 2. The refractory (Hf, Zr)O 2 skeleton structure possessed good thermal endurance, and the Ta-rich oxide melt filled the defects of the skeleton. [ABSTRACT FROM AUTHOR]

Molten calcium-magnesium-alumina-silicate (CMAS) corrosion has become a major constraint for the application of YSZ thermal barrier coatings (TBCs). In this paper, Al 2 O 3 and YSZ-Al 2 O 3 protective layers with a thickness of 50 μm were prepared on the surface of 8YSZ TBCs using air plasma spraying technology, and the progressive damage modes of the different TBCs under CMAS exposure were investigated, and the effects of the composition and microstructure of the protective layers on the infiltration and wetting behaviour of CMAS were compared. When the exposure time was shorter, the dense YSZ-Al 2 O 3 had a better impermeability barrier effect. As the interaction time between CMAS and the coating was prolonged, the structure and phase stability of YSZ-Al 2 O 3 were damaged, the thickness was thinned, and Al 2 O 3 had better stability and showed better protective effect. CMAS wettability was mainly related to the roughness of the coating surface, and the wettability was poorer on rough surfaces. [ABSTRACT FROM AUTHOR]

For metal-supported solid oxide fuel cells (MS-SOFCs), gadolinium-doped ceria (GDC) is one of the most promising electrolyte materials due to its high ionic conductivity. The plasma spraying technique has unique advantages in the preparation of MS-SOFCs, such as high efficiency, low cost, and low thermal impact on the metal support. However, few studies have been conducted on the preparation of dense GDC electrolytes using plasma spraying technology. In addition, it is not clear whether the composition and Ce valence state of GDC change during the plasma spraying process. In order to investigate this issue, GDC electrolytes were fabricated by atmospheric plasma spraying (APS) and vacuum plasma spraying (VPS) techniques. It is found that the GDC electrolyte fabricated by VPS is denser and has better electrochemical performance. The open circuit voltage and maximum power density of the VPS-cell at 600 °C are 0.90 V and 175.7 mW/cm2, respectively, while those of the APS-cell are 0.86 V and 124.8 mW/cm2, respectively. Moreover, the valence state of Ce4+ in the GDC electrolyte remains unchanged after plasma spraying, while the composition of Ce/Gd changes. This work successfully fabricates GDC electrolytes with qualified performance and provides a reference for further optimizing spraying parameters to prepare high-performance MS-SOFC. [ABSTRACT FROM AUTHOR]

This study reported the successful fabrication of Ti 2 AlC/Ti 3 AlC 2 composite coatings through plasma spraying Ti–Al–TiC agglomerated powders followed by post-annealing at 500 °C-1000 °C. Further, their microstructure evolution and mechanical properties were explored. Results indicated that only minor MAX existed in the as-sprayed coating accompanied by massive (Ti,Al)C x and substantial residual Al generated. The phase composition remained stable after annealing at 500 °C. Then the content of Ti 3 AlC 2 increased substantially in the coating annealed at higher temperatures (600 °C-700 °C) and decreased above 800 °C, accompanied by an increased Ti 2 AlC content. The contents of Ti 2 AlC and Ti 3 AlC 2 reached 26.35 % and 46.04 %, respectively, after annealing at 800 °C. Moreover, annealing could effectively eliminate defects such as pores and microcracks on the coating surface, and the thicknesses of all the coatings reached 100 μm. Notably, after annealing, the hardness of all coatings exceeded 700 HV, considerably higher than that of the as-sprayed coating. This study provides a novel way to fabricate MAX phase coatings with high content and certain thickness. [ABSTRACT FROM AUTHOR]

Understanding the damage evolution of thermal barrier coatings (TBCs) is crucial for optimizing TBCs systems and predicting service lifetime. This study investigates the correlation between mechanical properties and the thermal cycle lifetime of TBCs with conventional air plasma sprayed (APS) and micro-agglomerated particles embedded (EMAP) plasma sprayed structures, utilizing the Gd 2 Zr 2 O 7 (GZO) and GSc 0.075 Ce 0.3 Z (GSCZ) material systems. The damage evolution and cracking behavior of TBCs with varying material compositions and coating structures are evaluated using a combination of three-point bending tests and digital image correlation (DIC) techniques. Experimental results demonstrate that the thermal cycling lifetime of conventional APS TBCs correlates positively with the fracture toughness of the ceramic layer. Specifically, the conventional APS GSCZ coating with a fracture toughness of 1.12 MPa/m1/2 and the APS GZO coating with a fracture toughness of 0.97 MPa/m1/2 exhibit lifetimes of 34 cycles and 31 cycles, respectively. Moreover, the EMAP structural design exhibits notable advantages in enhancing the thermal cycle lifetime of TBCs across all material systems. DIC results confirm that strain accumulation during interface cracking of EMAP TBCs is effectively mitigated compared to conventional APS TBCs. The loose and porous characteristics of this structure significantly improve the compliance and interface fracture toughness of the TBC system, thereby alleviating TBC failure dominated by interface cracking. [ABSTRACT FROM AUTHOR]

The performance of plasma sprayed thermal barrier coatings (TBCs) is strongly dependent on the quality of the feedstock powders, which usually are fabricated by conventional spray drying and multi-step sintering methods. In this work, a novel supersonic plasma spheroidization technology was employed to fabricate the spherical nanocrystalline Sc 2 O 3 -Y 2 O 3 co-stabilized ZrO 2 (ScYSZ) powder. The deformation process from the irregular powder to the spherical one was stimulated by the COMSOL phase field simulation. The results suggested that the original irregular pyrolysis products of ScYSZ precursors were aggregated into spherical powders by plasma spheroidization technology. The COMSOL simulations verified that the powder changed from irregular particles to spherical ones. The spheroidized ScYSZ particles exclusively consisted of non-transformed t' -ZrO 2 phase and showed good fluidity, smooth surface and high apparent density, which were expected to have a broader application prospect in the field of TBCs and other ceramic coatings. [ABSTRACT FROM AUTHOR]

Poor fracture toughness and calcium–magnesium–aluminum–silicate (CMAS) corrosion resistance adversely affect environmental barrier coatings (EBCs) during prolonged service. Herein, an in-situ nanostructured Lu 2 O 3 /Lu 2 SiO 5 composite EBC was successfully prepared using nanostructured Lu 2 SiO 5 feedstocks. The morphologies and phase structures of the Lu 2 SiO 5 feedstocks and the corresponding coating were thoroughly characterized. Additionally, the mechanism of the in suit reaction of the Lu 2 O 3 /Lu 2 SiO 5 composite EBC was examined. The results indicate that the nanostructured as-deposited EBC exhibits a bimodal and dual-phase structure. The nanostructured Lu 2 SiO 5 coating comprises melted lamellae and unmelted or partially melted particles. The phase structure of these unmelted or partially melted particles includes Lu 2 O 3 and X2-Lu 2 SiO 5. The Lu 2 O 3 nanoparticles are formed by the decomposition of Lu 2 SiO 5 during spraying, and their content can be controlled to <15 %, which can enhance the fracture toughness and CMAS corrosion resistance of the EBCs to some extent. [ABSTRACT FROM AUTHOR]

Superalloys go through cyclic oxidation which refers to the progression of reputed exposure of materials to alternating oxidizing and non-oxidizing environments at high temperatures. The oxidation behavior of cobalt-based superalloy coatings depends on several variables, including the environment, surface roughness, manufacturing conditions, & coating composition. Because of their higher temperatures and protective oxide layer, coatings with a greater cobalt concentration are more oxidation-resistant. The behavior of oxidation is influenced by surface roughness, where rough surfaces offer greater surface area to oxidation while smooth surfaces decrease interaction with the environment. The microstructure and porosity of the coating are further impacted by processing variables used in thermal spraying, including temperature, particles velocity, and spray distance. Adding reactive components to the coating composition, such as silicon and aluminum, and applying post-treatments like nitriding or sealing are two ways to increase oxidation resistance. A greater temperature and particle speed can lead to a denser with less porous covering, improving the oxidation process resistance. The two typically used heat spraying techniques are high-velocity oxy-fuel (HVOF) and plasma spraying. To increase the resistance to oxidation of thermal spray cobalt-based superalloy coating, some strategies have been devised, such as inclusion of reactive materials, such as aluminum and silicon, which is the coating composition. These elements may establish an oxide layer protecting the coating's appearance, preventing further oxidation. [ABSTRACT FROM AUTHOR]

High‐temperature oxidation (1050°C) of Sr.9(Zr.9Yb.05Y.05)O2.85 (SZYY) thermal barrier coatings (TBCs) by suspension plasma spraying (SPS) and growth behavior of thermally grown oxide (TGO) were investigated. When the TBCs were exposed to high temperature for a period of time (∼5 h), the BC oxidized and TGO inevitably formed between the bond coating (BC) and the ceramic top coating (TC). The high‐temperature oxidation behavior of the BC is generally manifested as the growth of TGO, which has four specific stages as follows: (1) formative oxidation stage (0‒10 h), (2) rapid oxidation stage (10‒50 h), (3) stable oxidation stage (50‒100 h), and (4) complex oxidation stage (100‒200 h). The main component of early TGO is α‐Al2O3. It has a very low oxygen ion diffusivity and provides an excellent diffusion barrier, which has a positive effect on preventing further BC oxidation. However, as the heat treatment time increased, the Al consumption and the formation of a CNS layer (NiO, Co3O4, and spinel) in the BC eventually led to coating failure. The working life of TBCs can be improved by improving the ceramic TC structure and the Al content of BC. SZYY‐TBCs have certain potential application value. [ABSTRACT FROM AUTHOR]

To improve the ablation resistance of C/C composites, Y 2 O 3 with different contents modified HfC-MoSi 2 multi-phase coating was prepared by supersonic atmospheric plasma spraying. The microstructural and phase compositional evolution of as-prepared coating was studied both before and after ablation. The effect of Y 2 O 3 content on the ablation resistance and behavior of the coating was investigated in detail. The results showed that the incorporation of Y 2 O 3 enhances the high-temperature stability of SiO 2 oxide films and suppresses their volatilization at elevated temperatures. Furthermore, the formation of Y 2 Hf 2 O 7 and Y 2 Si 2 O 7 through the reaction between Y 2 O 3 , HfO 2 and SiO 2 promotes the development of a compact oxide scale, effectively inhibiting gas diffusion into the interior of the coating. Consequently, these improvements contribute to enhanced ablation resistance of the coating. [ABSTRACT FROM AUTHOR]

Double‐layer thermal barrier coatings are one of the development directions of thermal barrier coatings technology. LaYbZr2O7 (LYZO) has high toughness and low thermal conductivity, making it promising for use as a high‐temperature thermal barrier coating. However, its relatively poor mechanical properties, especially low fracture toughness, limit its further application. Therefore, we prepared a double‐layer coating of LYZO and Y2O3 partially stabilized ZrO2 (YSZ) using atmospheric plasma spraying, with the inner layer being YSZ and the outer layer being LYZO. The results showed that after spraying, LYZO was in the metastable fluorite phase, while YSZ was in the tetragonal phase. LYZO and YSZ had good chemical compatibility, and an interaction layer formed at the interface between them, with its thickness increasing with the sintering time. Eventually, after 100 h of heat treatment, the thickness reached 12 µm. The hardness of the LYZO/YSZ interface increased with the sintering time, reaching a maximum value after sintering at 1300°C for 10 h. When evaluating the interfacial bonding strength using indentation method, the length of cracks caused by indentation significantly decreased with the increase of sintering time. The increase in bonding strength can be attributed to the formation of a reaction layer and the reduction of thermal residual stresses. Raman spectroscopy was used to measure the thermal residual strain at the LYZO/YSZ interface. Unbalanced distribution of thermal residual stress and M phase was observed near the interface. As the sintering time increased, both thermal residual stress and M phase content decreased. In summary, the double‐layer thermal barrier coating of LYZO/YSZ has good potential for development. [ABSTRACT FROM AUTHOR]

The increasing demand for green hydrogen is driving the development of efficient and durable electrocatalysts for the hydrogen evolution reaction (HER). Nickel‐molybdenum (NiMo) alloys are among the best HER electrocatalysts in alkaline electrolytes, and here we report a scalable solution precursor plasma spraying (SPPS) process to produce the highly active Ni4Mo electrocatalysts directly onto metallic substrates. The NiMo coating coated onto inexpensive Ni mesh revealed an excellent HER performance with an overpotential of only 26 mV at −10 mA cm−2 with a Tafel slope of 55 mV dec−1. Excellent operational stability with minimum changes in overpotential were also observed even after extensive 60 hour high‐current stability test. In addition, we investigate the influence of different substrates over the catalytic performance and operational stability. We also proposed that a slow, but consistent, dissolution of Mo is the primary degradation mechanism of NiMo‐based coatings. This unique SPPS approach enables the scalable production of exceptional NiMo electrocatalysts with remarkable activity and durability, positioning them as ideal cathode materials for practical applications in alkaline water electrolysers. [ABSTRACT FROM AUTHOR]

Environmental barrier coating (EBC) can reduce the environmental susceptibility of turbine blades due to the increasing problems of high temperature oxidation and vapor corrosion in heating parts of aeroengine made by SiC/SiC. However, in addition to high-temperature corrosion, EBC may be subject to solid particle erosion (SPE) due to sands and peeled coatings. The erosion mechanism is insufficiently studied, and the impact erosion to SiC/SiC is seldom noticed. In this paper, the SPE behavior of SiC/SiC prepared by chemical vapor infiltration (CVI), which was coated with Si/Yb 2 Si 2 O 7 /Yb 2 SiO 5 rare earth silicate EBC prepared by atmospheric plasma spraying (APS), was studied, and the EBC-SiC/SiC were impacted in normal direction by SiO 2 particles with multiple particle sizes and flow rates. Scanning electron microscope (SEM) was used to observe the damage morphology, and the effects of different flow rates, energies and particle sizes on the SPE behaviors of EBC-SiC/SiC were analyzed. A meso-scale model of progressive damage method - finite element method (PDM-FEM) was built and the SiO 2 particle erosion mechanism for single layer SiC/SiC was simulated, analyzed and compared with the experimental results. [ABSTRACT FROM AUTHOR]

Bi 0.5 Na 0.5 TiO 3 -based ferroelectric materials with strong ferroelectricity and high Curie temperature have great application prospects in modern microdevices. In this paper, 0.92BNT-0.08BT ceramic coating was prepared by supersonic plasma spraying. The phase, microstructure, electrical properties and domain response of 0.92BNT-0.08BT ceramic coating were analyzed. The findings demonstrate that the 0.92BNT-0.08BT ceramic coating is without obvious structural defects and has a completely structure with good interface bonding. 0.92BNT-0.08BT ceramic coating has good electrical properties, the dielectric constant is 417, the dielectric loss is 0.3, and the remnant polarization is 16.6 μC/cm2. The piezoelectric force microscopy (PFM) results show that the 0.92BNT-0.08BT ceramic coating generally exhibits irregular and inhomogeneous striped nanodomains, with significant changes in amplitude and phase response under different electric fields. The results using switching spectroscopy-piezoresponse force microscopy (SS-PFM) show that the local piezoelectric coefficient (PR max) of the 0.92BNT-0.08BT ceramic coating reaches 754.3 p.m./V at a voltage of 20 V, and the ferroelectric domains exhibit a clear switching behavior. [ABSTRACT FROM AUTHOR]

Objective Methods Results Conclusion Soft tissue seal around implants ensures stable osseointegration and a long‐term survival of dental implants. Different surface modification and decontamination for implant abutments were endorsed in order to improve peri‐implant soft tissue healing, such as laser, plasma spray, acid etching, and steaming. The aim of this study was to evaluate the response of peri‐implant soft tissue to titanium abutments treated with Erbium‐doped: Yttrium‐Aluminum‐Garnet (Er:YAG) laser versus plasma spray.Twenty‐four patients who required implant placement in the maxillary arch participated in this study. Patients were divided into three groups, abutments treated with Er:YAG laser versus cold plasma spray and untreated abutments. Fourteen days following the implant abutment insertion, soft tissue peri‐implant biopsies were taken for histological, histochemical, and immunohistochemical evaluation. Scanning electron microscopy was done for the abutments; plaque index (PI) and gingival index (GI) were assessed 14 days and 3 months following final restoration.Regarding the histological results, the least mean inflammatory cell count was in the plasma group (174.09 ± 40.67), followed by the laser group (654.27 ± 85.95) and the control group (852.00 ± 117.98), with statistically significant differences between them. The mean area fraction of collagen fibers showed the highest value in the plasma group (9.73 ± 1.91), followed by the laser group (3.25 ± 0.49), while the lowest value was found in the control group (1.17 ± 0.51). The immunohistochemical expression of E‐cadherin was significantly higher and uniformly distributed in the plasma group (42.4 ± 11.2%) followed by the laser group (15.4 ± 4.07%) and the control group (6.8 ± 1.7%). SEM analysis of healing abutments showed fibroblast‐like cells, which were more developed with dense fibers in the plasma group; laser group fibers showed fewer and more delicate fibers than the plasma group, while no fibers were detected in the control group.Within the limitations of this feasibility study, the present data concluded that plasma spray and Erbium: YAG laser can be used for abutment surface treatment to achieve better peri‐implant soft tissue healing. Clinically and histologically, plasma spray showed a better effect on the peri‐implant soft tissues by reducing the inflammatory reaction, promoting collagen fiber formation, higher fibroblast‐like cell attachment, and upregulating E‐cadherin expression than Erbium: YAG laser and control groups. [ABSTRACT FROM AUTHOR]

RENbO4 ceramics have the potential to serve as a viable alternative to YSZ for advanced thermal barrier coatings. However, the fabrication of stoichiometric plasma spray RENbO4 coatings remains unexplored. Herein, we proposed a strategy to deposit a stoichiometric NdNbO4 coating using the atmospheric plasma spray technique. This was accomplished by the addition of excess Nb2O5 in feedstock powder to compensate for the evaporated Nb2O5 during the plasma spray process. The influence of powder composition and critical plasma spray parameters (CPSP) on the microstructure and phase formation of NdNbO4 coatings were characterized. Further, quantitative assessment of Nb2O5 evaporation with varying plasma parameters was also characterized using energy‐dispersive X‐ray fluorescence spectroscopy. Moreover, the support vector machines (SVM) model was used to construct a relation between the initial powder composition, CPSP, and stoichiometry of the coating. This strategy can be used for the fabrication of stoichiometric RENbO4 coatings for next‐generation thermal barrier coatings. [ABSTRACT FROM AUTHOR]

The NiCoCrAlY and NiCoCrAlYHf bond layer alloy was prepared by vacuum melting, followed by the deposition of a ZrO2-7%Y2O3 (7YSZ) ceramic coating on its surface using atmospheric plasma spraying. The cyclic oxidation process of the coating was systematically investigated through extensive analytical equipment and first-principles calculations and compared with conventional NiCoCrAlY coatings. It is demonstrated that NiCoCrAlYHf coatings exhibit greater resistance to oxidation and peeling than NiCoCrAlY coatings when thermally cycled at 1050 °C in air. The reason for this difference is that Hf doping can reduce the growth rate of the thermally grown oxide (TGO). In addition, the formation of HfO2 in the TGO layer, which delays the phase transition of Al2O3, reduces the growth of internal stresses in the coating and improves the adhesion of the TGO layer and bond strength of the interface. As a result, Hf doping significantly increases the oxidation lifetime of the coating, approximately 8 times that of NiCoCrAlY. [ABSTRACT FROM AUTHOR]

This study aimed to determine the effects of spray dried plasma (SDP) on growth performance, carcass traits, tibia quality, and hemagglutination inhibition titers in broilers fed two nutritional strategies with high or low nutrient density. In the study, 816 one-day-old Ross 308 male broiler chickens were divided into a 2 × 2 factorial arrangements consisting of four treatment groups with 12 replicates (17 birds/replicate) based on diets with high nutrient density (HND) or low nutrient density (LND) from d 0 to 42 and receiving either control or 1% SDP diets during d 0 to 10. The results showed that feed intake (FI) and body weight gain (BWG) were increased (P < 0.05) and feed conversion ratio (FCR) was significantly reduced (P = 0.003) for broilers fed HND diets from d 0 to 42. The inclusion of SDP increased the BWG (P < 0.001), FI (P < 0.001), and FCR (P < 0.05) during d 0 to 10 of broiler life but not effect of SDP was observed for the whole 0–42 d period. Carcass yield increased with HND (P < 0.001) and dietary SDP (P = 0.002). However, HND feeding significantly decreased liver (P < 0.001), bursa of Fabricius (P = 0.002), abdominal fat (P < 0.001), proventriculus (P < 0.001) and gizzard weight (P < 0.001), but increased heart weight (P = 0.013), although spleen weight remained unaffected (P > 0.05) on d 42. Tibial bone morphometric and mechanical properties improved (P < 0.05) with SDP supplementation, and bone ash, Ca, and P remained unaffected (P > 0.05) on d 14. With the exception at d 28 (P = 0.037), the antibody titer to ND virus was similar among all treatment groups (P > 0.05) at d 0, 14, and 42. In conclusion, HND diets improve performance of broilers during the whole period and SDP supplementation during starter phase improve performance at this period, but also increased carcass yield, and tibial quality. Therefore, inclusion of SDP in the starter diet could be a beneficial nutritional strategy to improve the health and production of broilers provided feeding strategies using various nutrient densities. [ABSTRACT FROM AUTHOR]

In this study, Al 2 O 3 –20TiO 2 (AT) and Cr 2 O 3 –3TiO 2 –5SiO 2 (CT) coatings were prepared by atmospheric plasma spraying (APS), The microstructure, phase compositions and corrosion behavior were studied comparatively. The results indicated that both coatings had layered structure, with an average surface roughness RA around 6 μm, an adhesive strength around 35 MPa, and a porosity around 4 %. The AT coating mainly composed of γ-Al 2 O 3 and α-Al 2 O 3 , and the CT coating composed Cr 2 O 3 respectively. Moreover, the AT coating exhibited better corrosion resistance than the CT coating. In artificial seawater, the corrosion process was strongly related to the porosity. The corrosion rate (based on the corrosion current density) of the two coatings showed a same trend which decreased first and then increased. It was thought that the blocking of early corrosion products in holes was helpful to delaying the progress of corrosion. In contrast, the later corrosion products would promote the formation and propagation of cracks, accelerating the corrosion. In the simulated environment with high pressure and hydrogen sulfide seawater, the corrosion process was strongly related to the porosity as well as the brittleness of the coatings. The corrosion rate (based on the weight loss) of the AT coatings still remained the same trend as it in the artificial seawater. However, the CT coating showed a continuously increasing corrosion rate, due to higher porosity and brittleness resulted in a large number of cracks under external stress, which offered corrosion channels. [ABSTRACT FROM AUTHOR]

Achieving high crystallinity levels, dense, crack-free microstructures with near-stoichiometric phase composition and controlled secondary phase formation are crucial for enhancing the performance of environmental barrier coatings (EBCs). To investigate the impact of APS process parameters on the as-sprayed crystallinity, microstructure, and phase composition of Yb 2 Si 2 O 7 EBCs, various spraying conditions were explored by adjusting torch power, nozzle size, powder feedrate, stand-off distance, and adding a shroud attachment to the torch. The velocity of particles controlled the density of the EBCs by an interplay between deposition efficiency and splat flattening ratios. Increasing nozzle size from 5/16″ to 1/2″ reduced particle velocity by up to 40 %, resulting in improved deposition efficiencies, porosity levels and coating thickness. However, larger nozzles led to higher silicon evaporation and up to 8 wt% more stable Yb 2 SiO 5 (I2/a) secondary phase was formed. Increasing the stand-off distance from 50 mm had minimal effect on microstructure, but metastable Yb 2 SiO 5 (P 21/c) was detected (up to 9 wt%) at longer stand-off distances of 100 and 150 mm. Raising the powder feedrate from 15 gr/min to 60 gr/min improved deposition efficiency (up to 9 %) and density (up to 15 %) of EBCs, yet resulted in higher silicon-depleted phase formation (up to 12 wt%). Adding a shroud to the torch nozzle exit led to severe silicon evaporation and formation of up to 42 wt% and 6 wt% of Yb 2 SiO 5 (I2/a) and Yb 2 O 3 , respectively. Moreover, due to the shroud's funnelling effect on smaller particles as well as particle overheating, porous microstructures with up to 28 % porosity levels were formed. High levels of crystallinity (∼75–91 %) were achieved in the as-sprayed condition for all the coatings, indicating real-time crystallization during spraying in all the spraying conditions. [ABSTRACT FROM AUTHOR]

Abradable environmental barrier coatings (EBCs) are used to reduce clearances between blades and casings in the hottest parts of aero gas turbines, increasing the overall efficiency of the turbine, however, research into the mechanical performance of such coatings is limited. The aim of this work was to better understand the relationship between microstructure and erosion and wear performance in abradable EBCs, since publicly available literature regarding such coatings is scarce and the potential efficiency gains in gas turbines are significant. In this study, ytterbium disilicate abradable EBCs containing three different porosity levels (determined by fugitive polyester phase addition) were deposited using atmospheric plasma spraying with porosity levels of 8, 15 and 21.5% by area. These coatings were then characterised in numerous ways; the porosity was quantified, the thermal conductivity was measured, the superficial hardness and erosion resistance were measured, and finally, the coatings were subjected to a rig test designed to simulate in-service cutting mechanisms against a tipped turbine blade. The results show that increasing the level of porosity via increasing the amount of pore forming phase in the feedstock, led to reduced erosion resistance and improved cutting by a turbine blade. [ABSTRACT FROM AUTHOR]

Thermal barrier coatings (TBCs) provide thermal protection for high-temperature components of aero-engines and steam turbines, but are susceptible to failure under thermal cyclic loads. The effective design of interfacial texture is one of the approaches to enhance the lifetime of ceramic TBCs. In this study, four types of interfacial textures were designed on the surface of substrates, and 8YSZ coatings of equal thickness were prepared using atmospheric plasma spraying, and thermal cycling tests were carried out. Meanwhile, the thermal cycle lifetime, microstructure evolution, residual stress, and energy release rate criterion were also studied. The optimal morphology and parameters of the texture are determined. It is found that the lifetime of the concave trapezoidal texture is the longest, with a deflection angle of 67°, diameter of 700 μm, depth of 500 μm, and spacing of 5 mm. This study can provide theoretical guidance for the interfacial texture design of ceramic TBCs. [ABSTRACT FROM AUTHOR]

Temperature-dependent nano SiC obtained from the polymer-derived ceramics method was used to modify ZrC coating by supersonic atmosphere plasma spraying. The crystallinity and grain size of SiC increased with increasing annealing temperatures. SiC annealed at 1400 °C exhibited the lowest crystallinity of 48.4 %, which led to massive re-pyrolyzing gas spillage from the modified ZrC coating during ablation, causing penetrating cracks. SiC annealed at 2100 °C exhibited the largest grain size of 190.4 nm, which could produce locally massive amounts of SiO 2 , accelerating the sintering of ZrO 2 in the coating and leaving maximum residual stress. SiC annealed at 1800 °C possessed a medium crystallinity of 81.5 % and a grain size of 12.2 nm, which was favorable to improve the ablation resistance of ZrC coating for forming fine-grained ZrO 2 scale with minimum residual stress. Our work provides a novel perception of the microstructure-property relationship for ablation-resistant coating under extreme conditions. [ABSTRACT FROM AUTHOR]

In this study, the (AlTiCrNbTa)O 2 high-entropy ceramic coating was fabricated by laser cladding with squash presetting. Prior to laser cladding, the atmospheric plasma sprayed NiCoCrAlY and Al 2 O 3 –TiO 2 coatings were deposited on steel substrate. The microstructure and element distribution of the (AlTiCrNbTa)O 2 coating were investigated by XRD, EDS, SEM and TEM in detail. The results showed that the feedstocks with various structures were successfully transformed into the (AlTiCrNbTa)O 2 high-entropy ceramic with single rutile structure through laser cladding. The (AlTiCrNbTa)O 2 coating had a thick and compact structure, which consisted of mainly uniform solid solution in rutile structure and partially segregated Al 2 O 3 with dendritic crystals structure. The (AlTiCrNbTa)O 2 coating combined tightly with the Al 2 O 3 –TiO 2 coating, and presented a high level of hardness (17.7 GPa) and elastic modulus (298.7 GPa). [Display omitted] [ABSTRACT FROM AUTHOR]

Al2O3-13wt. %TiO2 is a widely used coating material for the protection of metallic surfaces. The reduced graphene oxide (rGO) added alumina-titania composite coatings deposited using Air Plasma Spraying (APS) are used for enhancing the wear resistance of engineering components. In this work, the addition of rGO at varying weight percentages of 0.5, 1, and 1.5% to the Al2O3-13wt.%TiO2 powder resulted in composite coatings with improved microstructural characteristics, mechanical properties, and tribological performance. The use of SEM and XRD analyses revealed the presence of rGO between the coating splats, offering protection from crack initiation. Furthermore, there were noticeable changes in the microhardness and surface roughness of the coatings. Coatings reinforced with higher weight percentages of rGO had extremely low wear rates and offered a low coefficient of friction, with unpulled rGO acting as protective layers. However, it was also observed that the wear of coatings with 0.5 wt% and 1.0 wt% rGO addition was mainly due to the delimitation and subsequent pulverization at 1.5 kgf load and 0.17 m/s sliding speed. Overall, this work provides valuable insights into the use of composite coatings for enhancing the wear resistance of surfaces of components. [ABSTRACT FROM AUTHOR]

Plasma spray is a promising technology for surface protection and modification in many industrial application fields. However, the low adhesive or cohesive strength of the plasma sprayed coatings limited their further application. The cohesive strength was enhanced 115% ultra-sonicating the substrate during the plasma spraying process of Ni-10wt.%Al coatings. With the increase of power density from 0 to 1.32 W/cm2, the porosity, residual stress and strain were all decreased. However, when the power was further increased to 2.20 W/cm2, the porosity, residual stress and strain were all increased. Ultrasonic energy and the ultrasonic effects of acoustic pressure, acoustic streaming, heat effect, and cavitation effect would affect the physical processes of wetting, filling and solidification of the molten droplets during the plasma spraying process, affecting the microstructure and cohesive strength of the plasma sprayed coatings. The ultrasonic energy and ultrasonic effects which are affected by the ultrasonic power density affecting the fundamental physical processes is the key to enhance the cohesive strength of the plasma sprayed coatings. [ABSTRACT FROM AUTHOR]

Thermal radiation coating with low thermal conductivity and high infrared emissivity are desirable. In this work, a novel rare‐earth aluminate (PrAlO3+δ with rhombohedral structure) was synthesized via solid‐state reaction method, and the corresponding coating was fabricated using atmospheric plasma spraying (APS). The study encompassed an investigation into the phase structure, high‐temperature phase stability, thermo‐mechanical characteristics, and infrared properties. The results illustrate that as‐deposited coating contained amorphous phase, but recrystallized coating presented phase stability up to 1600°C. Furthermore, the recrystallized coating exhibited low thermal conductivity of 1.35 W/m K at 900°C as well as an average coefficient of thermal expansion of 10.36 × 10−6/K. Also, the coating exhibited high infrared emissivity related to high valance state (Pr4+) and oxygen vacancies. And the average infrared emissivity within 2–14 µm was 0.822 at 1300°C and presented slight decrease with the increase of temperature (the average infrared emissivity of 0.795 at 1800°C). [ABSTRACT FROM AUTHOR]

Purpose: Due to the harsh underground environment in coal mining, the surface of hydraulic support columns corrodes severely, resulting in significant economic losses. Therefore, a highly corrosion-resistant coatings is needed to extend the service life of the columns. Design/methodology/approach: This study aims to compare the corrosion resistance of ST-Cr3C2-NiCr (sealed treatment Cr3C2-NiCr) coatings with industrially applied chromium plating. The corrosion failure mechanism of the coatings was investigated. Findings: The results demonstrated that the ST-Cr3C2-NiCr coatings exhibited excellent corrosion resistance. After sealing treatment, the corrosion potential of Cr3C2-NiCr coatings was −0.215 V, and the corrosion current density of Cr3C2-NiCr coatings was lower than that of the plated parts. Practical implications: ST-Cr3C2-NiCr coatings prepared by supersonic atmospheric plasma spraying could provide excellent corrosion resistance in the coal industry. Originality/value: The low porosity and the presence of the NiCr phase were crucial factors contributing to the preferable corrosion resistance exhibited by the ST-Cr3C2-NiCr coatings. The corrosive process of the coatings involved layer-by-layer delamination of surface oxide film, sub-surface pitting, formation and degradation of sub-surface passive film, as well as severe block-like delamination. [ABSTRACT FROM AUTHOR]

Resin materials feature exceptional physical properties and inexpensive cost, but unfavorable surface characteristics, such as low wear resistance and poor erosion wear performance, render them tough to satisfy greater demands. The potential option is to prepare supersonic plasma sprayed Al 2 O 3 -13 wt%TiO 2 /Al 2 O 3 -phenolic resin (AT13/Al 2 O 3 -PF) coating on the surface of the resin matrix. AT13 feedstocks are classified into two types: Al 2 O 3 -13 wt%TiO 2 powder prepared by the agglomeration granulation process (AT13-1) and the mixture of spherical Al 2 O 3 and TiO 2 (approximately 13 wt%) powder (AT13-2). The effect of component dispersion on mechanical and tribological characteristics of coatings was thoroughly investigated, as well as the solid particle erosion wear behavior of coatings. The results illustrated that the evenly dispersed TiO 2 phase in AT13-1 coating was prone to homogenize the coating structure, resulting in better tribological characteristics than AT13-2 coating, although erosion wear performance was inferior to AT13-2 coating. The wear rate of AT13-1 coating was 1.36 × 10−5 mm3 (N m)−1, which was 1/21 times that of AT13-2 coating. At the 60° erosion angle, the high porosity of AT13-1 coating resulted in hard phase cracking or hard phase debonding. The high microhardness of AT13-2 coating reduced erosion wear at the 90° erosion angle. [ABSTRACT FROM AUTHOR]

Yttria-stabilized zirconia (YSZ) and TiO 2 - doped YSZ (TiYSZ) coatings were prepared using Atmospheric Plasma Spraying (APS) at different power levels to protect of flow passage components from cavitation erosion. We analyzed, the effects of TiO 2 doping and spraying power on the coatings' phase structure, microstructure and mechanical properties using XRD, Raman spectroscopy, SEM, Vickers hardness and nano-indentation. We tested the cavitation erosion behavior of TiYSZ coatings and YSZ coatings (as a reference) in a laboratory setting employing vibration-induced cavitation in accordance with ASTM standard G32-16. The results showed that the YSZ coating contained 50% c-phase and 50% t-phase, while the TiYSZ coating contained approximately 78 % c-phase. Spraying power hadlittle effect on the phase structure of either coating. However, higher spraying power increased the density of the coating, leading to greater microhardness. TiYSZ coatings were denser than YSZ at any power level and did not exhibit a distinct microcolumnar grain structure, unlike YSZ. Additionally, TiYSZ coatings displayed better mechanical properties, including higher hardness, elastic modulus, toughness, and fracture strength compared to YSZ. As a result, the cavitation resistance of TiYSZ coatings improved by about 50% compared to YSZ. Furhermore, we found that chemical degradation of YSZ-based ceramics under cavitation erosion conditions plays a role in cavitation erosion. We also observed that cavitation-induced amorphization is a key mechanism contributing to this degradation. [ABSTRACT FROM AUTHOR]

In this paper, CaO–B 2 O 3 –SiO 2 (CBS) is utilized as matrix material of microwave coating for the first time to achieve high-performance microwave absorption under high-temperature. A series of FeSiAl (FSA)/CBS composite coatings were prepared via atmospheric plasma spraying. The impact of spraying power on the microstructure, electromagnetic properties, and high-temperature stability of as-sprayed coatings were studied. The experimental results reveal that CBS could effectively suppress the formation of the lamellar structure of FSA as the low initial melting temperature, also form unexpected Fe 2 SiO 4 structure with FSA during the spraying process. The increase in complex permittivity of the coating is primarily attributed to enhanced coating density and the development of Fe-rich regions within the CBS matrix. Furthermore, the dense coating prevents the oxidation of FSA and exhibits high-temperature stability. Our coating of 1 mm thickness has a reflection loss below −5 dB with frequency range of 7–14.8 GHz at 500 °C. [ABSTRACT FROM AUTHOR]

This study concentrates on NiCrAlY-based coating with nano-boron carbide and cenosphere particles. The composition of NiCrAlY, B4C and cenosphere are maintained the same for all the samples. The plasma spray technique is used for coating. The erosive wear is carried out for different impingement angles of 30°, 60°, 75° and 90° at 900°C. The morphology of coating before and after erosive wears is studied using scanning electron microscopic analysis. Further, the study is carried out on surface roughness, scratch resistance and coefficient of friction of the eroded surface of the samples. The significant erosive wear resistance is reported for an impact angle of 60° followed by 30°. The surface roughness results reveal the formation of deep craters and the ploughing effect of material on the coatings. The scratch test and COF show the presence of coating and the brittle nature of the failure of the coating. [ABSTRACT FROM AUTHOR]

The microstructure, mechanical performance, and tribological properties of SiC ceramic coatings prepared via atmospheric plasma spraying (APS) and chemical vapor deposition (CVD) method were compared to provide good anti-wear protection for carbon/carbon composites. The surface morphology of the APS-SiC coating was characterized as having a porous structure, whilst the CVD-SiC coating presented with many pyramidal-shaped crystals constituting the surface. The APS-SiC coating consists of a dominating SiC phase and a small fraction of the Si phase, while the XRD pattern of the CVD-SiC coating mainly consists of the SiC phase. The dense crystalline microstructure of the CVD-SiC coating made it possess a higher hardness and Young's modulus at 31.0 GPa and 275 GPa, respectively. The higher H/E and H3/E2 parameters of the CVD-SiC coating implied that it exhibited better plastic resistance, which is also beneficial for anti-wear properties. The scratch test reflected the critical loads of the spallation of the APS-SiC coating and CVD-SiC coating, which were evaluated to be 25.9 N and 36.4 N, respectively. In the tribological test, the friction coefficient of the APS-SiC coating showed obvious fluctuations at high load due to damage to the SiC coating. The wear mechanism of the APS-SiC coating was dominated by abrasive wear and fatigue wear, while CVD-SiC was mainly dominated by abrasive wear. The wear rate of the CVD-SiC coating was far below that of the APS-SiC coating, suggesting the better wear-resistance of the CVD-SiC coating. [ABSTRACT FROM AUTHOR]

Atmospheric plasma spraying (APS) allows deposition of ceramic coatings on metallic substrate, significantly increasing the wear resistance of the component. Coating's microstructure and consequently its properties, depend on heat treatment of the feedstock particles. This property can be controlled by process parameters, especially electric power and spray distance. On the other hand, some plasma torches allow introducing another variable, an injection mode, which could be realized in external or in internal way. In the presented research, wear resistance of Al2O3+13 wt.% TiO2 coatings deposited under various values of spray distance and different injection modes were examined using ASTM G-99 procedure. The impact of spraying parameters on the coating's microstructure was established and connected to the functional properties of the manufactured deposits. Observed differences indicated influence of injection mode and spray distance value. Coatings deposited with internal feedstock injection exhibit lower porosity and slightly higher hardness than these made with external injection mode. In terms of wear resistance for both spray distance the wear factor was lower for internal injection system. Obtained results confirmed assumed thesis, that internal injection mode improves heat treatment and consequently ameliorate wear performance of plasma sprayed alumina-titania coatings. [ABSTRACT FROM AUTHOR]

Solid particle erosion is a severe problem for a machine working in a sandy environment. Due to this service, life of instruments decreases as comparision to the requirement. In this research, the elemental composition of Ni50Ti50 has been taken to coat mild steel substrate at different substrate preheating temperatures (100, 200, 300 and 400 °C). An atmospheric plasma spraying procedure has been used to spray uniform deposition of NiTi powder on the mild steel substrate. After coating, an x-Ray diffractometer (XRD), scratch tester and scanning electron microscopy (SEM) were applied to measure the surface property. The wear property was investigated by air jet erosion test rig at 45° and 90° impingement angles. Again, the eroded surface morphology was investigated by SEM. Various phases such as NiTi, Ti2Ni, Ni3Ti, Ni4Ti3, Ti2O, TiO2 and NiO are obtained by XRD analysis. NiTi and their intermetallics (such as Ni4Ti3, Ni3Ti, TiO2) play an important role in forming dense splat formation and higher hardness. Several erosion mechanisms were obtained, such as scratches, splat fragmentation and plastic deformation. It was noticed that the erosion rate is relatively low at low substrate preheating temperatures compared to higher preheating temperatures. Scratch wear resistance for low preheating temperature is high as compared to high preheating temperature due to variations of NiTi intermetallic phases on the coating surface. [ABSTRACT FROM AUTHOR]

Abradable seal coatings represent a critical technology within the realm of advanced power systems, designed to minimize airflow channel leakage, thereby reducing energy consumption and enhancing overall efficiency. In the present study, CuAl/BN, CuAlLaF3/BN, and CuAlY/BN abradable seal coatings were prepared using plasma spraying technology. Both the as-deposited coatings and high-temperature oxidation-treated coatings were comprehensively investigated by means of scanning electron microscopy (SEM), open-circuit potentials (OCP), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), salt-spray corrosion testing, and bond strength evaluations. The results show that the addition of rare earth elements to the CuAl/BN coatings does not enhance the corrosion resistance of the coatings and even leads to a decrease in the corrosion resistance of the coatings. In contrast, the CuAlY/BN coatings exhibited a significant improvement in corrosion resistance following an oxidation treatment at 550 °C. This enhancement is attributed to the yttrium (Y) element, which facilitates the formation of passivation films and confers a resistance effect, thereby bolstering the coatings' resistance to corrosion. The bond strength of the high-temperature oxidation-treated CuAlY/BN coating was improved by about 30% after 960 h of salt-spray corrosion. [ABSTRACT FROM AUTHOR]

This paper presents and demonstrates the development of a new lightweight coating for aluminum alloy from a novel multicomponent alloy based on the AlSiMgCu system. The coating was applied using a newly designed approach that combined high velocity oxy-fuel (HVOF) and plasma spraying processes. This hybrid technique enables the deposition of coatings with enhanced performance characteristics. The optical microscopy (OM) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM + EDS) revealed a strong adhesion and compaction between the multicomponent coating and the A6061 substrate. The new coating improved hardness by 50% and increased electrical conductivity by approximately 3.3 times compared to the as-cast alloy. Corrosion tests showed a lower corrosion rate, comparable to thermally treated A6061 alloy. Tribological tests indicated over 20% reduction in friction and over 50% reduction in wear rate. This suggests that multicomponent aluminum coatings could improve automotive and parts in contact with hydrogen by enhancing hydrogen fragilization resistance, corrosion resistance, electrical conductivity, and wear properties, with further optimization of thermal spraying potentially boosting performance even further. [ABSTRACT FROM AUTHOR]

Yb-doped Y2O3 stabilized ZrO2 (YbYSZ) coatings, developed through solution precursor plasma spraying (SPPS), are engineered to resist calcium–magnesium–alumino–silicate (CMAS) infiltration by leveraging their unique micro-nano structures. This provides superior anti-wetting properties, crucial for preventing CMAS penetration at high temperatures. The investigation focused on the structural and compositional changes in YbYSZ-SPPS coatings subjected to prolonged thermal exposure at 1300 °C. Results indicate that while the coatings undergo significant sintering, leading to densification and microstructural evolution, the elemental composition and phase stability remain largely intact after up to 8 h of heat treatment. Despite some reduction in CMAS resistance, the coatings maintained their overall protective performance, demonstrating the potential of SPPS coatings for long-term use in high-temperature environments where CMAS infiltration is a concern. These findings contribute to the development of more durable TBCs for advanced thermal protection applications. [ABSTRACT FROM AUTHOR]

There is a high demand for plasma-resistant coatings that prevent the corrosion of the internal ceramic components of plasma etching equipment, thereby reducing particle contamination and process drift. Yttrium oxyfluoride (YOF) coatings were prepared using atmospheric plasma spraying (APS) with commercially available YOF/YF3 powder mixtures; namely YOF 3%, YOF 6%, and YOF 9%. The etching behaviour of YOF and yttrium oxide (Y2O3) coatings was investigated using an inductively coupled plasma consisting of NF3/He. X-ray photoelectron spectroscopy (XPS) showed that the YOF 6% coating had the thickest fluorinated layer. The scanning electron microscope (SEM) examination revealed that the YOF 6% coating showed exceptional resistance to erosion and generated a reduced quantity of contaminated particles in comparison to Y2O3. Consequently, it is more suitable as a protective material for the inner wall of reactors. The YOF coatings exhibit excellent stability and high resistance to erosion, indicating their appropriateness for use in the semiconductor industry. [ABSTRACT FROM AUTHOR]

The results of experiments aimed at studying the dependence of the adhesion strength of a coating deposited onto a screw-shaped surface of a part through plasma spraying depending on technological spraying modes. Results of correlation and regression analyzes are presented. [ABSTRACT FROM AUTHOR]

Pristine SiC coating prepared by plasma spraying is difficult to achieve good ablation resistance at high temperature due to its weak SiO2 scale. Besides incorporation by ultra-high temperature ceramics, the modification of the SiC coating from its feedstock powder is necessary. In the current work, the mixed powders of SiC, Si and C, where the SiC was encapsulated and then carbonized by polydopamine, denoted as SiC@C–Si, were employed as the feedstocks, compared with the mixed case, i.e. SiC–Si–C. The SiC@C–Si coating exhibited superior anti-ablation properties, with a linear ablation rate of 0.62 μm/s, 57 % lower than the SiC–Si–C coating. This is attributed to the fact that nano-carbon formed by carbonization of polydopamine is more prone to reacting with Si than micron-sized C powder, thereby forming a dense microstructure after ablation. Besides, in-situ formed SiC by the depletion reaction increases the flow resistance and decelerates the failure of SiO2 film, thus improving the ablation resistance.

In order to improve the wear and corrosion resistances of magnesium alloys and broaden their application areas, a layer of Al-20%(mass fraction) Al2O3(abbreviated as Al-Al2O3) coating was firstly deposited on the surface of the magnesium alloy substrate by cold spraying method as the transition layer of the composite coating, and then an Al2O3-13%(mass fraction) TiO2(abbreviated as AT13) surface layer was prepared on its surface by atmospheric plasma spraying method, thereby obtaining an Al-Al2O3/AT13 composite coating. Subsequently, the surface and cross-sectional morphology of the transition layer and surface layer were analyzed by scanning electron microscopy, and the microhardness and bonding strength of the composite coating were measured using a microhardness tester and a universal testing machine. Moreover, the friction coefficient and wear rate of the composite coating were measured by a friction and wear tester, and the corrosion behavior of the composite coating in a 3.5%(mass fraction) NaCl solution was investigated through dynamic potential scanning technology. Results showed that the microhardness of the Al-Al2O3 transition layer and the AT13 surface layer were(42.3±13.7) HV0.1 and(838.8±87.6) HV0.1, respectively, and the bonding strength of the Al-Al2O3/AT13 composite coating was 31.2 MPa. Additionally, the stable friction coefficient and wear rate of the composite coating were 0.74 and 5.94×10-5 mm3/(N·m) under a load of 40 N and a wear condition of 10 min, and compared with the magnesium alloy substrate [1.89×10-4 mm3/(N·m)], the wear rate was reduced by 68.6%. After being immersed in a 3.5% NaCl solution for 30 min, the corrosion potential of the composite coating was-927 mV, and the corrosion current density was 1.81×10-5 A/cm2. Compared to the magnesium alloy substrate, the corrosion potential increased by 742 mV, and the corrosion current density decreased by an order of magnitude.

With the application of shrouds made of silicon carbide ceramic matrix composite（SiC-CMCs），the abradable coating technology suitable for SiC-CMCs is urgently needed. The four-layer structure of BSAS（Ba0.75Sr0.25Al2Si2O8）-polyester-based abradable environmental barrier coating （A/EBCs） was prepared by atmospheric plasma spraying. The influence of process parameters on the porosity and the structural evolution of the layer at 1300 ℃ were investigated. The phase structure，microstructure and coating composition were characterized by XRD，SEM，EDS and TEM respectively. The results show that the porosity of BSAS-polyester abradable top layer is 26.4%-36.8%. And the temperature-sensitive parameters of BSAS-polyester particles are primary gas （argon） flow，second gas （hydrogen） flow and spraying distance. In contrast，the speed-sensitive parameters are primary gas （argon） flow. The primary gas （argon） flow has the opposite effect on the particle temperature and velocity of the BSAS-polyester. The abradable surface layer is oxidized at 1300 ℃ for 300 h and maintains monoclinic phase structure，stable stucture and composition，and locally precipitates spherical amorphous silicon oxide particles. Furthermore，the coating abradability was evaluated by high-temperature and high-speed scraping test. Nano-scale Ni-based superalloy particles adhesion on the surface of the coating are found，and the blade incursion depth ratio （IDR） is 20%，which meets the requirements of the abradable sealing coating.

Plasma spraying is a prospective method frequently employed because of its increased effectiveness in ceramic coatings. Optimizing process parameters is necessary to maximize the coating performance. This study employed response surface methodology (RSM) to investigate the impact of process variables, including current, powder feed rate, and standoff distance, on the porosity and corrosive wear loss of Cr3C2+8YSZ composite coating. Experiments were done using the central composite design method, and quadratic regression models were created for the responses based on the completed trials. All parameters are observed to be most significant as the obtained p-value is under the threshold of 0.05 as per the analysis of variance (ANOVA) calculations. The optimal plasma spray process parameters were determined to be 500 A of current, a powder feed rate of 46gm/min, and a standoff distance of 3 inches for the expected lowest corrosive wear loss of 0.000025mm/year and a reduced area percentage porosity value of 0.93. [ABSTRACT FROM AUTHOR]

The effects of reduced graphene oxide (rGO) as an additive on the microstructure, mechanical properties, and tribological behavior of air plasma sprayed (APS) nanostructured tungsten carbide–cobalt (WC-25 wt.%Co) coatings were studied. The rGO was added in three distinct weight percentage proportions of 0.5, 1, and 1.5 wt.%. The microhardness and surface roughness of the APS sprayed nanostructured WC-25 wt.%Co coatings reinforced with rGO were changed significantly. Microstructural alterations in the coatings were also noticed with the addition of additives. Gluing of rGO amid coating splats was also seen in the microstructure of the coatings. The coatings' microstructure revealed the presence of tungsten (W), tungsten carbide (WC), and semi-tungsten carbide (W2C) as the primary phases. The existence of the W2C phase in the microstructure of the coatings was mostly due to the decarbonization of WC at higher temperatures during plasma spraying. It was also found that the amount of wear of the coatings was exceptionally low because the rGO could not be extracted from the 1.5 wt.% rGO-reinforced coatings particularly. The wear degradation in the 0.5 and 1.0 wt.% rGO added coatings was mostly due to delimitation and the subsequent pulverization, notably at loads and sliding speeds of 1.5 kgf and 0.17 m/s. [ABSTRACT FROM AUTHOR]

This paper presents a study on thermally sprayed coatings. Coatings produced by high-velocity oxygen–fuel spraying HVOF and plasma spraying deposited on the A03590 aluminum casting alloy are tested. The subject of this research concerns coatings based on tungsten carbide WC, chromium carbide Cr3C2, composite coatings NiCrSiB + 2.5%Fe + 2.5%Cr, mixtures of tungsten and chromium powders WC-CrC-Ni, mixtures of carbide powders with the Cr3C2-NiCr + the composite 5% NiCrBSi and WC-Co + 5% NiCrBSi. The aim of this research is to find a coating most resistant to the erosive impact of particles contained in the medium centrifuged by industrial rotors. The suitability of the coating is determined by its high level of microhardness. The hardest coatings are selected from the coatings tested and subjected to abrasion tests against a sand particle impact jet and the centrifugation of a medium with corundum particles. It is found that the most favorable anti-erosion properties are demonstrated by a coating composed of a mixture of tungsten carbide and chromium carbide WC-CrC-Ni powders. It is concluded that the greatest resistance of this coating to the erosive impact of the particle jet results from the synergistic enhancement of the most favorable features of both cermets. [ABSTRACT FROM AUTHOR]

Gradient environmental barrier coatings (EBCs) were fabricated via atmospheric plasma spraying to deposit Yb 2 Si 2 O 7 -Yb 2 SiO 5 onto a laser-sculpted SiC substrate, with varying mass ratios. Experimental results reveal that the gradient coating exhibited remarkable integrity, showing no signs of cracking even after exposure to 90% H 2 O-10% O 2 (g) water vapor corrosion at 1300 ℃ for 100 h. Besides, the thickness of the thermally grown oxide (TGO) layer was minimal (18.53 ± 1.08 μm) compared to 75Yb 2 Si 2 O 7 -25Yb 2 SiO 5 single layer EBCs (24.93 ± 1.62 μm) with similar integrity under water vapor environment for 100 h. The superior performance of the gradient coating against water vapor corrosion can be attributed to the outmost layer containing more Yb 2 SiO 5 with excellent vapor corrosion resistance, while the innermost layer primarily comprises Yb 2 Si 2 O 7 , providing significant damage resistance and resilience to thermal shock. These favorable attributes make the gradient coating a promising candidate for EBC application in aerospace. [ABSTRACT FROM AUTHOR]