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The lifespan of plasma-sprayed thermal barrier coating (TBC) systems is difficult to predict owing to the variety of microstructures and deterioration histories. In this study, we developed a novel TBC damage model to reflect deterioration histories; thus, it can be applied to various TBCs. Damage to TBCs is classified into oxidation and mechanical damage; therefore, a detailed deterioration history can be reflected. In addition, by introducing a virtual S–N diagram, a life prediction model that can be applied to TBCs with various microstructures was established. We used the proposed damage and life prediction models in isothermal aging and thermal cycle tests with different aging cycles. The predicted lifespan of TBCs by using the proposed models was within 95% of the results obtained by performing actual tests in the temperature range of 1150–1350°C.

In this work, the corrosion behaviors of as-plasma sprayed Yb2SiO5 and LaMgAl11O19 coatings under an environment with a volumetric ratio of 90% H2O-10% O2 were investigated at 1300 °C. The results showed that Yb2SiO5 and LaMgAl11O19 coatings had good water vapor corrosion resistance. Therefore, Si/Yb2SiO5/LaMgAl11O19 tri-layer EBCs were designed and prepared to completely cover the surface of SiCf/SiC by using atmospheric plasma spraying (APS). The water vapor corrosion behaviors of SiCf/SiC with and without EBCs at 1300 °C were investigated. The results showed that tri-layer coating can provide better corrosion resistance for SiCf/SiC at a high-temperature steam environment at 1300 °C. By comparing the water vapor corrosion behaviors of single-layer coatings and the tri-layer EBCs under same corrosion environment, it was found that the thermal mismatch stress and the formation of TGO is the main causes of tri-layer coating failure.

The erosion behavior of three different cermet coatings namely, Al2O3, Al2O3 + 3% TiO2 and Al2O3 + 13% TiO2 was studied in order to perform erosion analysis. The coatings were sprayed using Plasma spray gun in a simulated coal-fired boiler conditions on SAE-347H steel. An optical profilometer was put to use in order to find weight loss, erosion profiles and erosion rate (mm3/g) in term of volume loss. All the Plasma gun sprayed cermet coatings were able to protect SAE-347H steel from erosive wear at incident angles of 30°, 60° and 90°. In case of uncoated SAE-347H steel specimens the solid particle erosion (SPE) rate was highest at an incident angle of 30°, nominal at incident angle of 60° and lowest at incident angle of 90°.

A Ni60/Ni-WC composite coating was fabricated by the plasma spraying technology and microstructure of the coating was analyzed. Moreover, erosion resistance of the coating under different erosion angles was tested. Results demonstrated that the coating has lamellar structures and contain some pores. WC particles distribute evenly in the coating and bond well with the parent phase. When the erosion angle increase, the weight loss of the erosion-induced coating increases firstly and then decreases, showing plastic-brittle composite erosion characteristics.

The possibility of increasing the complex of physical, mechanical and operational properties of plasma sprayed coatings from powders of the PG-19M-01 and PRH18N9 grades due to the electric pulse effect on the heterophase high-temperature flow during spraying and next surface plastic deformation of the deposited coatings by shot blasting has been investigated. It is shown that shot blasting provides the formation of a hardening layer with a thickness of up to 180...200 μm, while the maximum level of microhardness is observed at a depth of about 60 μm. The microhardness of the coating from PG-19M-01 powder at the point of maximum hardening increases by 35%; steel coatings from PR-H18N9 powder – by 48% compared to the state after spraying. Experimental studies of the effect of this treatment on the bond strength and wear resistance of the obtained coatings have been carried out. It is shown that after shot-blasting the bond strength of the coatings decreases by 10...15%, and the wear resistance increases by 32...38%.

Current study deals with the effect of carbon nanotube (CNTs) and graphene nanoplatelets (GNPs) reinforcement on the mechanical properties and the adhesion strength of plasma sprayed alumina (Al2O3) single splats, using in-situ picoindentation and nanoscratch test, respectively. The hardness of the Al2O3 splat was measured as 18 ± 5.3 GPa which increased to 34.22 ± 8.44 GPa on 1 wt% CNTs addition and to 42.5 ± 9.06 GPa on 0.5 wt% GNPs addition. Hybrid addition of CNTs and GNPs provided the maximum hardness value of 51.25 ± 8.76 GPa to the Al2O3 splat. Similar trend in the elastic modulus has been reported with a minimum value for Al2O3 splat, i.e. 159 ± 35.40 GPa, and maximum for the Al2O3 splat mixed synergistically with CNTs and GNPs (269 ± 43.12 GPa). Adhesion strength of the Al2O3 splat (0.21 ± 0.11 MPa) also showed a nearly 5-fold increase on hybrid addition of CNTs and GNPs with a maximum value of 1.08 ± 0.38 MPa. This improvement in the properties were due to the extremely high mechanical properties of CNTs and GNPs and better melting of the splats, which not only improved the densification but also provided a better interlocking between the splat and the substrate.

metal supported solid oxide fuel cells (PMS-SOFCs) are regarded as a promising choice for power generation. 430 L steel is a popular choice for SOFC support due to its acceptable electrical perform...

High performance absorbing coatings attract great interest because of the urgent demand for radar stealth technology. However, most reported absorbing coatings focused on the incident microwave were perpendicular to the surface of the coatings. Here, a kind of absorber of TiC/Al2O3 was prepared by plasma spraying method and the influence of TiC content and oblique incident microwave irradiation on the absorbing properties of TiC/Al2O3 were reported. The absorbing performance firstly increased and then decreased with increasing the TiC content due to the impedance matching and attenuation constant cannot match well at the same time. Meanwhile, compared with TE polarization, TM polarization of the plasma-sprayed TiC/Al2O3 coatings was more sensitive to the incident angle. This study demonstrates the feasibility of plasma-sprayed TiC/Al2O3 absorbing coatings for electromagnetic applications.

In the research, the effect of different critical plasma spray parameters (CPSP) on the microstructure and mechanical properties of plasma-sprayed LMA coatings with thickness of 797 μm were investigated. As a result, the porosity of coatings was increased from 12.14% to 24.88% with the decrease of CPSP from 1.20 to 0.86, while bonding strength of coatings was obviously reduced from 15.98 ± 0.36 MPa to 4.87 ± 0.7 MPa. Relatively, Young's modulus and hardness of the coatings exhibited a decreasing tendency with the decrease of CPSP. When the CPSP was decreased from 1.20 to 0.97, the residual compressive stress of coating surface varied from −162.10 ± 12.13 MPa to −93.49 ± 3.28 MPa, and that obtained from cross-section was decreased from −116.02 ± 5.92 MPa to −70.68 ± 3.99 MPa. Meanwhile, the fracture toughness of coating was improved from 0.62 ± 0.05MPa⋅m1/2 to 1.34 ± 0.05 MPa⋅m1/2, which was higher than that of cross-section of coating. The microstructure and mechanical properties of LMA thick coatings were strongly dependent on the CPSP.

Plasma spray grade Al2O3-13TiO2 and ZrO2 powders were blended physically in different proportions (80 wt% Al2O3-13TiO2 + 20 wt% ZrO2, 20 wt% Al2O3-13TiO2 + 80 wt% ZrO2 and 50 wt% Al2O3-13TiO2 + 50 ...

This paper reports the unusual ion sorption of zinc ions to the structure of solution-precursor plasma-sprayed hydroxyapatite coatings studied via X-ray photoelectron and Raman spectroscopy techniq...

Phosphate coatings have been produced by plasma-spraying hydroxyapatite (HA) and tricalcium phosphate (TCP) powders onto Ti substrates at initial temperatures of 20, 300, and 550°C, followed by hydrothermal treatment (HTT) at 650°C, and the variation in the phase composition of the coatings has been examined in relation to the phase composition of the plasma-sprayed powders: 100 wt % HA, 100 wt % α‑TCP, and 100 wt % β-TCP. The as-prepared coatings produced by plasma-spraying the HA powder consisted of 87–91 wt % HA and 9–13 wt % CaO, and after HTT their phase composition was 89–93 wt % HA and 7–11 wt % CaO. The coatings produced by plasma-spraying the α-TCP powder at initial substrate temperatures from 20 to 550°C consisted entirely of a crystalline α-TCP phase. The coatings produced by plasma-spraying the β-TCP powder consisted of both β-TCP and α-TCP, and the content of the latter phase decreased from 100 to 80% as the substrate temperature was raised from 20 to 550°C. After HTT, the coatings contained 26–28% HA, independent of the phase composition of the starting TCP powders.

Recently, multifunctional coatings offering simultaneous tribological benefits and protection from adverse environments are gaining widespread attention. While, metallic coatings offer excellent durability, their performance is limited to ambient temperature. In this study, it is shown that plasma sprayed Graphene nanoplatelates (GNPs) reinforced CeO2 (CG) coatings offer excellent tribological properties both at room and high temperature. Interestingly, unlike conventional coatings where wear property degrades at high temperature, the wear properties of CG keeps on improving from RT to 873 K. Maximum reduction in wear rate (260%) and COF (26%) was observed at 873 K. It is believed that this coating could pave the path for designing coatings operating at high temperature.

Nanoparticle growth during laser remelting was studied to provide references for optimizing technological parameters. The variations of nanoparticle sizes during laser remelting plasma-sprayed presetting of nanostructured Al2O3-13 wt%TiO2 coating were investigated on the basis of the classical theories of grain growth and by combining the temperature courses of nanoparticles at different positions, which were obtained from laser remelting finite element numerical simulation of the temperature field. Moreover, the effects of initial nanoparticle size and different remelting positions on grain growth were analyzed. A laser remelting test was conducted on the corresponding plasma-sprayed nanostructured coating. Results show that the overall trend of nanoparticle growth in the laser remelting test is consistent with theoretical calculation results, indicating that the classical theory of grain growth can offer some theoretical guidance to understanding nanoparticle growth during laser remelting.

The effects of SiC on microstructure and properties of plasma sprayed ZrB2–ZrC composite coating were investigated. Plasma sprayed ZrB2–ZrC and ZrB2–ZrC–SiC composite coatings were prepared and compared. The addition of SiC could improve the density of the ZrB2–ZrC–SiC coating that lead to better mechanical properties. The reason was that SiC improved the melting state of powder feedstocks during plasma spraying process and refined grains in ZrB2–ZrC–SiC composite coating.

Erosion can cause the progressive material loss of thermal barrier coating system (TBCs), raising a challenging problem when gas turbine engines operate in extreme conditions. Therefore, detecting the erosion of coatings plays a crucial role in health monitoring of TBCs. In this work, atmosphere-plasma-sprayed (APS) TBCs specimens were fabricated with five different embedded luminescent sublayers (YSZ:Eu, YSZ:Tb, YSZ:Dy, YSZ:Er, YSZ:Sm, each is 50 μm thick) in the ceramic top coat for each TBCs specimen. To accelerate the erosion rate for detection purpose, a specially designed erosion testing machine was employed in the experiments. In addition, we developed a device to capture the distinctive emission of the exposed luminescent sublayers after erosion and thereby proposed an optical method to detect the erosion in the TBCs. For the specimens embedded with the luminescent sublayers, the size and depth of the eroded area were efficiently determined by the luminescence imaging with a relatively high accuracy.

The preparation, microstructures, complex permittivity and the electromagnetic interference (EMI) shielding properties of plasma-sprayed ZrB2/Al2O3 ceramics were investigated. The sprayed ceramics displayed high dielectric losses in terms of a high imaginary part of the complex permittivity in the range of 120–150, indicative of exceptional EMI shielding performance. The total EMI shielding efficiency (EMI SE) of 30 wt% ZrB2 filled Al2O3 ceramics is greater than 31 dB at 25℃ and 44 dB at 600℃ in the range from 8.2–12.4 GHz with a thickness of 1.2 mm. In addition, the ZrB2/Al2O3 ceramics still maintain high EMI SE and a long-term life at high temperature (600℃ for 300 h). Therefore, ZrB2/Al2O3 ceramics may be good candidates for high temperature EMI shielding materials with high EMI shielding efficiency and a long-term life.

Yttria stabilized zirconia (YSZ) based composite topcoats were prepared with three advanced ceramic materials as second phase component; CaZrO3, (La0.75Nd0.25)2Zr2O7 and Nd2Ce2O7. The solid particles erosion (SPE) testing of the air plasma sprayed composite topcoats was carried out at room temperature and 900 °C to study the effects of second phase on erosion behavior. The erodent was angular fused alumina of 40-45 mm size. The erosion mechanism was followed in all topcoats with cracking and fracturing of the plasma sprayed splats due to erodent particles impact and impingement, whereas micro-ploughing was observed after 900 °C SPE testing as an additional feature. The hardness and intrinsic properties of second phase component in the composite topcoats played a crucial role in improving the erosion rate (ER) at ambient as well as 900 °C. The Nd2Ce2O7/YSZ topcoat show lower ER due to combatively higher hardness of Nd2Ce2O7 and good interfacial bonding with YSZ. The overall lowering of ER at 900 °C as compared to that of at ambient conditions was ascribed to the anelastic mechanical response of the ceramic topcoats due to thermal cycling involved in the SPE testing at high temperature.

We have studied the effect of heat treatment conditions on the size and number of pores in plasma-sprayed aluminum oxide parts. Samples 100 × 100 × 2 mm in dimensions have been characterized by X-ray computer tomography, qualitative phase analysis, and scanning electron microscopy. The results demonstrate that the number and size of pores vary nonmonotonically with increasing heat treatment temperature, which is due to the heating-induced polymorphic transformations of aluminum oxide, accompanied by changes in the average density of the material and the associated changes in its volume. The temperature dependences of the number of both small and large pores have extrema at ~1100°C. At this temperature, the number of small pores decreases drastically, whereas the number of large pores increases. Further raising the temperature to 1300°C leads to an inverse process: the number of small pores increases drastically, whereas the number of large pores drops sharply. This is due to the transformation of δ-Al2O3 into α-Al2O3, which occurs very rapidly and is accompanied by a large increase in the density of the material of the plasma-sprayed parts and its embrittlement.

Statement of problem Soft-tissue attachment to different surfaces may play a pivotal role in the long-term success of dental implants. However, studies on the issue, especially on newer materials, are sparse. Purpose The purpose of this in vitro study was to evaluate the viability and adhesion of human gingival fibroblasts (HGFs) on different implant abutment materials with specific surface modifications. Material and methods One hundred and fifty specimens in 6 experimental groups were evaluated: smooth-machined titanium alloy (Ti), laser-modified titanium (TiL), smooth-machined polyetheretherketone (PEEK) (P), laser-modified PEEK (PL), plasma-treated PEEK (PP), laser- and plasma-treated PEEK (PLP). Machined Ti was considered as the control group. Surface roughness (Sa), water contact angle (WCA), and X-ray photoelectron spectroscopy (XPS) were measured. HGF attachment and proliferation were observed at 1, 3, and 7 days after cell seeding. Comparison of the means among the groups was performed with 1-way analysis of variance (ANOVA) with post hoc comparison using the Tukey test (α=.05). Results Sa values of the laser modified groups were significantly higher than those of the nonmodified (smooth-machined) groups (P .05). On the first and third days of proliferation, the plasma sprayed groups (PP, PLP) showed significantly greater proliferation than all experimental groups (P .05). Conclusions Laser-modified titanium and PEEK surfaces led to guided gingival fibroblast attachment. Plasma treatment of PEEK surfaces increased the wettability of this polymer and improved proliferation of HGF.

The aim of this study was to determine the counter body effect on the wear behavior of TiO2-45 Cr2O3 coating. The commercial TiO2-45 Cr2O3 coating powder was deposited onto the surface of the AISI 316 L substrate using the APS method. Dry sliding wear tests were performed with Al2O3 and WC-Co counter body balls under different loads (5 N, 10 N, and 15 N) and reciprocating frequencies (1 Hz, 2 Hz, and 3 Hz). The COF values obtained from the Al2O3 ball were found to be higher than that of the WC-Co ball. In general, increasing load and sliding speed caused higher wear volume values for both counter body balls. When using Al2O3 ball under the 5 N load, a higher amount of wear debris and crack formation was observed, whereas, for higher loads, a larger plastic deformation zone which has lots of pitting and spalling was determined. As for the WC-Co ball, swelling-induced spallation and delamination were recorded as the effective wear mechanisms as well as the plastic deformation.

In this work, the yttria stabilised zirconia ZrO2 + 8 wt % Y2O3 (YSZ) coatings were studied. The coatings were manufactured by a relatively new method based on liquid feedstock, named: suspension plasma spraying (SPS). The main aim of the study was to investigate the influence of one of the fundamental process parameter, stand-off distance, on the YSZ coating mechanical properties, namely adhesion, cohesion, hardness, and dry sliding wear resistance. Moreover, the coatings surface morphology and microstructure were investigated. Despite the fact, that in the SPS method the heat flux into the substrate is much higher than in conventional atmospheric plasma spraying (APS), for stand-off distance as short as 40 mm, the structure has not been damaged by thermal stresses. The results revealed that shorter spray distance leads to obtaining coatings characterised by higher cohesion and adhesion to the substrate as well as higher hardness and resistance to sliding wear. The wear mechanism of both YSZ coatings relies on the adhesive mode, which is intensified by severe coating material delamination.

This paper presents the results of the investigation of NiCrRe coating deposited by plasma spray process at the atmospheric pressure on boiler steel substrate. These coatings were characterized by means of a scanning electron microscopy, and Energy-dispersive X-ray spectroscopy. The wear resistance of plasma sprayed NiCrRe coatings has been investigated under dry sliding conditions at applied load of 10 N in air. The continuous stiffness measurement (CSM) method was used for the investigation of nanohardness using Agilent G200 Nano-indenter in order to determine the mechanical properties of the coatings. Microstructural observations pointed out that the NiCr layer with white isles of rhenium possessed porosity, oxidized, un-melted and semi-melted particles, and inclusions. According to the results the thickness of the layer is 450 µm, the indentation modulus 158 ± 24.4 GPa, hardness 3.74 ± 0.76 GPa and the coefficient of friction is 0.45.

In this work, the effects of spraying power on the microstructure, orientation, magnetic and dielectric properties of plasma sprayed cobalt ferrite coatings were investigated. With the increase of spraying power, the compactness of the coatings was increased, and the orientation degree of was also increased. However, the thickness and dielectric constant of the coatings were increased first and then decreased. The melting degree, which was induced by spraying powers, was the key factor to affect the microstructure and properties of the coatings.

Plasma spraying was employed to deposit an Al coating in order to create a self-metallurgical bonding effect through impact-induced melting with highly overheated molten droplets. Numerical simulation was employed to estimate the interface temperature between the molten Al splat and the Al substrate. The interface bonding was examined from cross sections of the Al splat and the etched coatings. The results show that, with Al droplets higher than 1800°C, impact-induced Al substrate melting occurs. The measurements showed that, during spraying, most Al particles were heated to temperatures theoretically causing an impact-induced melting effect, which subsequently produces a metallurgical self-bonding effect. The observed results confirm the metallurgical bonding in plasma-sprayed Al coating.

In the present study, the microstructure development and properties of the starting Fe-B-C powders for plasma spraying fabricated by dispersing a consumable rotating rod were investigated as functions of alloying elements additions. These powders were prepared in the following compositional ranges: B (10…14 wt.%), C (0.01…0.5 wt.%), Me (0…5.0 wt.%), where Me – Cr, V, Mo or Nb, balance Fe. Structural properties were characterized by etallography, X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. Mechanical properties of the powders were measured by a Vickers indenter. Compression strength, oxidation resistance, and melting temperature were also determined. Chromium or vanadium were found to dissolve completely in Fe2(B, C) and Fe(B, C) constituent phases of the Fe-B-C powders replacing iron and forming substitutional solid solutions. By entering into the iron borides structure, these alloying elements improve ductility and oxidation resistance but lower melting temperature and hardness of the powders. Molybdenum or niobium were mainly found in secondary phases such as Mo2B, Mo2(B, C) or NbB2 at the Fe2(B, C) boundaries. As a result, these alloying elements enhance hardness, oxidation resistance and melting temperature of the powders.

Aim of this study: To compare marginal bone loss around machined and plasma sprayed dental implant collar surfaces after 24 months follow up period in mandibular overdenture cases. Materials and methods: Eight patients with completely edentulous ridges received 32 implants; each patient received 4 implants at the lower arch; 2 machined collar implants were placed at one side and 2 plasma sprayed collar implants were placed at the other side. The implants were loaded 3 months after placement. Radiographic marginal bone loss was measured using CBCT at time of implant placement (baseline), 3,6,12 and 24 months follow up periods. Result: Marginal bone loss was observed for both machined and plasma sprayed implant collars throughout the follow up periods with statistically significant decrease in bone level through 24 months follow up period. Conclusion: Plasma sprayed implant collar promoted better bone repair with less bone loss than did machined implant collar.

Al2O3-ZrO2 and Al2O3-ZrO2-TiO2 composite coatings were prepared by plasma spraying. The effects of TiO2 on the microstructure evolution and thermal shock resistance of the Al2O3-ZrO2 coating at hig...

Both tensile and shear adhesion strength tests were performed to evaluate interfacial strength between hydroxyapatite coatings on titanium alloy substrates subjected to anodization and heat treatment prior to deposition as well as post-deposition heat treatment. Results of the tensile adhesion strength tests were influenced by the size of the blasting media and the processing of pre- and post-heat treatments but not influenced by anodization. The finite element method (FEM) analysis of stress distribution during the shear adhesion strength test was also performed to evaluate the degree of stress singularity. The results show that the stress singularity parameters were dominant factors of stress distribution in the stress singularity fields, and they were also expected to influence the “essential” interfacial strength. In addition, the size of the blasting media had the same influence on the shear and tensile adhesion strength tests. This suggests the possibility of estimating tensile adhesion strength using the results of shear adhesion strength.