Marcin Drajewicz

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 Influence of Overaluminizing on TGO Formation on Thermal Barrier Coatings Deposited by Low Pressure Plasma Spraying and Chemical Vapour Deposition Methods on Rene 80 Nickel Superalloy

The paper presents results of research into isothermal oxidation test of thermal barrier coatings characterized by high oxidation resistance and hot corrosion. Bondcoats were deposited by overaluminizing of MeCrAlY–type coating deposited by LPPS method. The outer ceramic layer of yttrium oxide stabilized zirconia oxide (Metco 6700) was deposited by plasma spray physical vapour deposition (PS-PVD). For comparison purposes additionally LPPS-sprayed were MeCrAlY bondcoats, which were not subsequently aluminized.. The isothermal oxidation test at 1100oC for 1000h shown that thickness of the TGO layer in overaluminized bondcoat was significantly thicker in comparison with conventional LPPS-sprayed MeCrAlY bondcoats.

The Effect of the Aluminide Coating on the Thermal Properties and Oxidation Resistance of Inconel 625 Ni-Base Superalloy

An investigation was conducted to synthesize βNiAl coating on the nickel based superalloy Inconel 625 in the low activity chemical vapor deposition process (CVD). The deposition was carried out for 8 hours at 1050°C using the BPXpro3252 IonBond company equipment. Surface morphology and cross-section microstructure of the diffusion coating were studied and compared using an optical microscope, an X-ray diffractometer and a scanning electron microscope (SEM) equipped with an energy dispersive spectroscope. It was found that 29 μm thick aluminide coating consisted of two layers: an outer one and the inner interdiffusion one. The outer layer consisted of the βNiAl phase. The inner one consisted of the βNiAl phase with chromium, molybdenum and niobium carbides (M23C6 and MC type) inclusions. Outer layer hardness was about 564 HV0.002 while interdiffusion layer hardness was about 725 HV0.002. Thermal diffusivity of Inconel 625 superalloy with and without coating was measured using a NETZSCH model 427 laser flash diffusivity apparatus. The thermal diffusivity measurements were conducted in the argon atmosphere at the temperature interval 20 - 1200 oC. Thermal diffusivity of the uncoated Inconel 625 Ni-base superalloy at the room temperature is about 2 mm2/s, while for the coated superalloy thermal diffusivity is about 2.8 mm2/s. The increase of the temperature from 20 to 1200 oC leads to the increase of the thermal diffusivity of the coated sample from 2.8 to 5.6 mm2/s. Cyclic oxidation tests for both coated and uncoated superalloys were performed at 1100°C for 1000 h in the air atmosphere. The aluminized samples exhibited a small mass increase and the α-Al2O3 scale was formed during the oxidation test.

Microstructural Characterization of Thermal Barrier Coatings Deposited by APS and LPPS Thin Film Methods

In the paper first results of TBCs deposition by LPPS-Thin Film method were presented. The LPPS-Thin Film is a new type of processes for deposition of thermal barrier coatings. In this method deposition of thin ceramic layer in very low pressure is possible as well as coatings with columnar structure (in plasma spraying-physical vapour deposition process). The MeCrAlY bond coats were deposited by APS method. The overaluminising by CVD method of conventional MeCrAlY was also conducted. The analysis of microstructure of both type bond coats as well as outer ceramic layer were presented using light and scanning electron microscopy methods. Results of EDS microanalysis showed the increasing of aluminum content in outer zone of overaluminized MeCrAlY coating. In ceramic layer the columnar structure were observed which was connected with powder evaporation during plasma spraying. The new type of MeCrAlY-NiAl bondcoat could increase the oxidation of TBCs deposited by LPPS Thin Film method.

The technology of TBC deposition by EB-PVD method

The role of thermal barrier coatings is to ensure heat resistance of elements in the hot section of turbofan aircraft engines in high temperatures. Stages of the production process are made up of preparing the base material, forming the aluminide interlayer by chemical vapour deposition method and depositing of the ceramic coating. The paper presents results of tests into microstructure of ZrO2 and Y2O3 ceramic coatings formed by EB-PVD method. The microstructure was assessed in several spots of the turbine blade of a high pressure turbofan engine by means of determining the coating thickness as well as height and width of ceramic columns, depending on the forming conditions.

Microstructure and Isothermal Oxidation Resistance of Thermal Barrier Coatings Deposited by LPPS, CVD and PS-PVD Methods on Inconel 617 Nickel Superalloy

The paper presents results of research into thermal barrier coatings characterized by higher oxidation resistance. Bondcoats were formed by overaluminizing of the MeCrAlY coating, deposited by low pressure plasma spraying (LPPS). The outer ceramic layer of yttrium oxide stabilized zirconia oxide was deposited by plasma spray physical vapour deposition (PS-PVD). For comparison purposes additionally formed were MeCrAlY bondcoats, which were not subsequently aluminized. The research showed that during CVD overaluminizing there was formed an additional layer built of the β-NiAl phase, which protects the base material from oxidation. Preserved below it increased chromium content ensures resistance to hot corrosion. The outer layer was characterized by columnar structure, similar to that obtained in the EB-PVD process. The isothermal oxidation tests showed that thickness of the TGO layer into overaluminized bondcoat significantly thicker in comparison with conventional LPPS-sprayed MeCrAlY bondcoats.

The Properties of Refined Glasses with Aluminum Hydroxide Nano-Molecules

New refining technology of soda – calcium – silicon glass surfaces with inorganic compounds nanomolecules has been presented in the study. In order to determine modification of the glass surface SEM observation and EDX analysis have been carried out. The glass samples were subjected to the UV-VIS, photo-elasticity and ellipsometry examinations. From obtained results follows, that refining of the glass surface by nanopowder aluminum hydroxide compounds provides forming of very thin surface layers. This type of modification improves physical glass properties. As the example results of microhardness refined glass are presented in the article.Keywords: glass, surface, nanoparticles, refining

The Formation of TBCs Using LPPS, CVD and PS-PVD Methods on CMSX-4 Single-Crystal Nickel Superalloy

In the paper new type of thermal barrier coatings characterized by good oxidation and hot corrosion resistance were presented. Bond coats were formed by overaluminizing of an MeCrAlY type coating deposited by low pressure plasma spraying (LPPS). The outer ceramic layer of yttria stabilized zirconia (Metco 6700) was deposited by plasma spray physical vapour deposition (PS-PVD). Rene 80 nickel superalloy was used as base material. The research showed that double-layer bond coat was formed with external NiAl phase layer and inner MeCrAlY layer. The outer ceramic layer was characterized by columnar structure similar to that obtained in the EB-PVD process. The presence of secondary reaction zone (SRZ) was noted.