Papers by Keyword: Ceramic Coatings

Abstract: Plasma Spray Physical Vapour Deposition (PS-PVD) is one of the promising methods considered as an alternative to Electron Beam Physical Vapour Deposition (EB-PVD) process used for production of ceramic columnar layer for turbine blades protection against high temperature. The PS-PVD method enables to control the coating structure. In presented article the dense to columnar structure was formed during single-step PS-PVD process using yttria stabilized zirconia oxide (YSZ). The ceramic coating was deposited using LPPS-Hybrid (Oerlikon-Metco) system at Rzeszow University of Technology. The IN 713 alloy with aluminide coating produced by CVD method was used as a base material. The inner zone of the ceramic coating was characterized by dense structure and the outer was characterized by columnar structure. The influence of power current, gas composition flow, powder feed rate and coating time on thickness of both zones was investigated using Scanning Electron Microscopy method. The relationship between process parameters and thermal conductivity was also investigated using Laser Flash Method (LFA). Conducted experimental process showed that using of 1800A power current higher Ar flow (80 NLPM) as well as powder feed rate (30 g/min) enables to obtain dense structure of coating. When higher energy of plasma (power current 2200 A, plasma gasses flow (Ar-35 NLPM, He-60 NLPM) and lower powder feed rate was used the columnar zone was formed. The thickness of obtained coating was in range 140-200 μm. The formation of thick dense layer increased the overall thermal conductivity of coating in comparison with conventional columnar ceramic layer. The combination of thin 20 μm dense-zone with thick (120 μm) columnar zone reduces thermal conductivity of whole coating.

Abstract: The plasma spraying is commonly used in medical application. The Atmospheric Plasma Spray (APS) method was applied for production of yttria-stabilized zirconia (YSZ) on AISI 316L stainless steel surface and also on Ti6Al4V titanium alloy surface. In present article two examples of coatings production were presented. In first experimental the YSZ was plasma sprayed (APS) on 316L stainless steel surface. The coating was deposited using A60 (Thermico) plasma torch. The initial parameters were selected and it was concluded that minimal power current was 500A. The thickness of obtained coating was in range 100-150 micrometers. The X-ray phase analysis showed the presence of tetragonal t-phase of ZrO₂. The lamellar structure of coatings with large porosity was observed. In second experimental the newly developed Plasma Spray Physical Vapor Deposition method (PS-PVD) was used. The YSZ coating was deposited on titanium Grade 5 surface. The conducted research showed the formation of two types of coatings structure. When the power current was lower (2000 A) the dense lamellar-like coatings was obtained. If the power current was increased (up to 2200A) the columnar ceramic coating was observed.

Abstract: In this study, thermal and optical properties (emittance and reflectance of solar radiation) of different colors ceramic tiles for use in outside surfaces were measured. Although widely used in the brazilian residential market, these materials are not properly characterized with respect to these properties. The thermal emittance measures were performed using an emissometer (D&S pattern SA1) and the solar reflectance using a spectrophotometer UV-Vis-NIR (model Lambda 1050). These properties are important for the determination of Solar Reflectance Index, SRI, that may help designers and consumers to choose the appropriate materials to make their buildings more energy efficient and comfortable. The SRI indicates the ability of a surface to reflect solar radiation and mitigate the temperature rise of surfaces, being used in LEED certification (Leadership in Energy and Environmental Design) to evaluate the performance of some opaque elements in constructions. The studies revealed a wide variation of SRI (values are between 72 and 22) in the same product with different colors. In particular two samples showed SRI lower than 29, which place them even below the minimum requirement of LEED for application in some types of outside surfaces, as steep roofs and pavement materials (LEED v. 2009 used in Brazil).

Abstract: The PS-PVD method is a promising technique for production of ceramic coatings from the vapor phase on gas turbine components. The resulting layers combine benefits of coatings made by the plasma spray method and other methods of Physical Vapor Deposition. The plasma spray process is carried out under reduced pressure (~ 200 Pa) and with the use of a gun applied in the method (the LPPS torch 0C3P). The PS-PVD enjoys many of the benefits of plasma spray methods combined with relatively low production costs and overall better properties. One of the significant costs of coating manufacturing by this method is the use of helium as process gas to generate plasma. The authors attempted to form a ceramic coating from ZrO₂, where a mixture of argon and nitrogen in various proportions was used. The resulting layers were analyzed by XRD, LFA, SEM-EDS.

Abstract: Pre-alloyed powder of Ti-47Al-2Cr-2Nb-0.15B was prepared by a gas atomization process and powder metallurgy (PM) γ-TiAl alloys were made through a hot isostatic pressed (HIPed) route. The atomized powders were canned in containers, degassed, sealed, and HIPed. Effect of two different canning materials (mild steel and commercial pure titanium (CP-Ti)) on the microstructure and properties of as-HIPed γ-TiAl alloy were discussed. Due to the reaction between mild steel containers and γ-TiAl at relative high temperature (over 1230 °C), the γ-TiAl matrix is contaminated. CP-Ti canned γ-TiAl showed bigger yield and fracture strength than mild steel canned TiAl. PM γ-TiAl alloy parts having complex shape could be manufactured by the near net-shape process.

Abstract: Electrophoretic deposition (EPD) of ceramic frits is shown to be a useful coating method for different metal surfaces and geometries since it allows obtaining very smooth surface finishes with precise control of their thickness. By the other hand, these kind of coatings show differences with the coatings obtained by conventional wet application methods as dipping, flow-coating, slushing and spraying. At this point, CIDETEC has used an own advanced ceramic coating based on no commercial enamels to determinate the best application method to obtain an excellent anticorrosive coating on carbon steel. In view of possible scaling up to particular industrial applications, a detailed characterization of the microstructure, morphology, physical, chemical and mechanical properties of the coatings was performed. The preliminary studies show that EPD system improves the characteristics of this coating.

Abstract: This manuscript was used to test feasibility that the Al2O3 ceramic composite steel plate was fabricated by Self-propagating High-temperature Synthesis (SHS).The Al2O3 ceramic coatings were prepared on the steel plates.The ceramic coatings had been subsequently characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) attachment. The results showed that the ceramic coatings could be divided into three layers called Al2O3 ceramic layer, Fe/Al2O3 blending layer and iron layer from the roof to the bottom. Al2O3 ceramic layer had many porosities and low density. The tissue structure of Fe/Al2O3 blending layer was compact and had no porosities.

Abstract: The network SiC ceramics was prepared by organic foam impregnation and pressure-less sintering technology. The co-continuous SiC_n/Mg composites were fabricated by vacuum infiltration methods. The results proved that coarse surface was observed on the surface of SiC network ceramics, which was helpful for interface reaction of metal alloy during impregnation process. The continuous interface can be formed in the SiC_n/Mg composites. KF concentration had more important influence on coatings morphologies and polarization behaviors of SiC_n/Mg composites during micro-arc oxidation process.Key words: Interpenetrating, Ceramic Coatings, Micro-arc Oxidation

Abstract: Coatings of polysilazane-based ceramics are a promising technology for the protection of steels for applications at high temperatures and chemically harsh environments where, currently, special and expensive grades of steel are used for. To this work, the polymer-ceramic transformation behavior of VL-20 polysilazane precursor and 8%YSZ and glassceramic powders as fillers, and their variables were evaluated, and the coatings on stainless steel AISI 304 substrates were characterized. The first obtained coatings showed good adherence, but also high porosity.

Abstract: The micro-arc oxidation technology were utilized to fabricated the ceramics coating in order to improve the corrosion resistance of Ti–6Al–4V alloy (TC₄). The sodium silicate solution was introduced into the electrolyte solution for increasing the coating properties. The effect of the sodium silicate content on the phase composition, surface morphology and potentiodynamic polarization behavior was investigated. The results showed that the increase of Na₂SiO₃ concertration was benefit to improve corrosion resistance of the MAO coating of TC₄ alloy. Key words: Micro-arc oxidation, Ceramic Coatings, Corrosion Resistance.