Kamil Dychtoń

Thermal Properties of YSZ Powders for Plasma Spraying

The oxides in the case of theirs properties are important materials for industrial application especially, in aircraft industry for application as thermal barrier coatings. Thermal properties of zirconium oxide stabilized by yttria are better than other ceramic materials. This powder could be stabilized in room temperature by addition of rare earth elements. In this article the thermal analyses of yttria stabilized zirconia (YSZ) oxide are presented as a baseline for future measurements of thermal properties of YSZ powder with addition of rare earth elements. The thermal expansion, specific heat, thermal diffusivity and thermal conductivity of commercially available Matco 6700 powder offered by Sulzer Metco company were analyzed by thermal methods.

Process Temperature Effect on Surface Layer of Vacuum Carburized Low-Alloy Steel Gears

Gears, due to their complex shape, carried load and required accuracy are ones of most complex aircraft engine parts. Single tooth damage usually breaks the power transmission and causes failure of the entire gear system. Adequate sustainability and guarantees of transmission is therefore a condition for secure operation of whole device. Particularly high requirements for reliability are put to transmissions used in the aerospace industry. Due to the loads which are transmitted through the gears, the materials used by the manufacturer must have not only high strength but also show the abrasion resistance of the surface layer and the ductility of the core. Thermo-chemical treatment of industrial gears is a fundamental process, which gives them adequate mechanical properties regarding loads they carry and the surface conditions of work. The most promising method in the discussed field is vacuum carburizing, which by its specification of work significantly reduce the emission of CO2 and the duration of the process, without reducing the quality of the final product. The main aim of the paper is to present criteria for selection of carburizing parameters (mainly temperature increase) as a part of thermo-chemical treatment process performed using vacuum methods. Proper (higher to compare with conventional methods) carburizing process temperature is crucial in programming of carbon diffusion process meaning in process time and final carburized layer characteristics as carbon profile and homogeneity of the carburized layer.

The Influence of Sodium Molybdate on the Rate of Corrosion of Aluminum in Phosphoric(V) Acid

Corrosion rates of aluminum in phosphoric (V) acid solutions were determined gravimetrically in a presence of sodium molybdate which acts as an inhibitor. Inhibition efficiencies were calculated. The most effective corrosion inhibition was observed for 0.5 M H3PO4 and 100 mM of Na2MoO4. Since insoluble corrosion products precipitated onto specimens and influenced the determined corrosion rates, an analysis of a morphology of the specimens was performed by using a scanning electron microscope. The corrosion products are composed of Mo, P, Al and O. An Mo/P atomic ratio varied between 0.8 and 1.6 depending on the concentrations of phosphoric (V) acid and sodium molybdate. For three concentrations of H3PO4, the concentration ranges of sodium molybdate, where the gravimetric method may be applied were determined.

The replacement of chromate by molybdate in phosphoric acid-based etch solutions for aluminium alloys

ABSTRACT Corrosion inhibition of aluminium alloys in the acidic solutions is important in the aluminium finishing industry (stripping solutions for anodic films). Sodium molybdate is a potential replacement for chromate-containing species used in the stripping solutions. It was tested as the corrosion inhibitor of 2024 aluminium alloy in orthophosphoric acid solutions. A corrosion rate of the alloy as a function of an initial concentration of sodium molybdate and temperature was determined by using gravimetric and gasometric methods. The corrosion rate was significantly lower in the solutions containing over 5 mM of sodium molybdate when compared to the uninhibited solution. The inhibition efficiency decreased with the increase of the temperature for the constant concentration of sodium molybdate. Sodium molybdate reduced the corrosion of the alloy by adsorption as well as formation of insoluble corrosion products on the alloy.

The Influence of Ar/N2 Plasma Gases on Microstructure of Ceramic Coatings Produced by PS-PVD Method

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.

Influence of Low Pressure Plasma Spraying Parameters on MCrAlY Bond Coat and its Microstructure

Low pressure plasma spraying (LPPS) is one of the most advanced processes of an MCrAlY bond coat formation. It ensures the forming of metallic coatings free of oxides which can act as an bond coat for thermal barrier coatings used, among others, for protection of turbine blade surface. The paper presents results of tests into microstructure of coatings made from AMDRY 997 powder on the base of type Inconel 617 heat-resistant nickel alloy. The tests were carried out using light and scanning electron microscopy. Evaluated was the influence of spraying conditions on microstructure, porosity and thickness of the obtained coating. Test results show that the LPPS method allows to form coatings of low porosity and free of oxides which can be used as an bond coat in thermal barrier coatings.

Thermal Analysis of Halide Activator Used in Aluminizing of TiAl Intermetallics

A detailed study of thermal analysis of ZrCl4 was carried out to investigate the influence of the halide salt type activator on the growth behavior of coating formed in vapor phase aluminizing process and subsequently to identify the most suitable condition. The equilibrium partial pressures of vapor species generated at the decomposition temperature of ZrCl4 were calculated by using a procedure based on minimization of the whole Gibbs energy with Factsage 6.2 using Fact 53 and SGsold thermodynamic databases. The results were discussed and compared with literatures. With the aid of thermodynamic analytical tools, chloride salt activator was analysed and the decomposition temperature with related enthalpy change was evaluated.