Marek Góral

The technology of Plasma Spray Physical Vapour Deposition

Abstract The article presents a new technology of thermal barrier coating deposition called Plasma Spray – Physical Vapour Deposition (PS-PVD). The key feature of the process is the option of evaporating ceramic powder, which enables the deposition of a columnar ceramic coating. The essential properties of the PS-PVD process have been outlined, as well as recent literature references. In addition, the influence of a set of process conditions on the properties of the deposited coatings has been described. The new plasma-spraying PS-PVD method is a promising technology for the deposition of modern thermal barrier coatings on aircraft engine turbine blades.

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.

Microstructure of TBC Coatings Deposited by HVAF and PS-PVD Methods

High velocity air fuel (HVAF) is one of the high velocity flame spraying process (HVFS). The HVAF method employs a combination of liquid fuel mixed in a chamber with compressed air to obtain high velocity flows. This technology can provide high deposition levels, adequate bond strength as well as high dense coating structure. The working principle of Plasma Spray – Physical Vapor Deposition (PS-PVD) is based on evaporation of the ceramic powder, which enables advanced microstructure of the deposits. In this paper, microstructure of Thermal Barrier Coating (TBC) deposited by HVAF and PS-PVD method was described.

The Influence of Activator on Vapour Phase Aluminizing of TiAl Intermetallics

The paper presents results of research into the aluminizing process of TiAl intermetallics. The substrate was Ti48Al2Cr2Nb intermetallic alloy. The BPX Pro 325S CVD system was used for aluminizing process. Used in the experimental were four types of activators: AlCl3, AlF3, ZrCl4 and HfCl4. During the aluminizing process 2 kg of Al-Cr granules were put in a container. The deposition process was carried out in argon atmosphere for a duration of 4 hours at the temperature of 1000°C. The XRD and chemical analysis were conducted. The results showed than aluminide coatings contained TiAl2 and TiAl2 phases were formed using an AlF3 activator. In other processes the amount of Al in the coatings was smaller than in the substrate. The obtained results showed that for the aluminizing process use of aluminum fluorides is necessary.

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.

Influence of Deposition Parameters on Structure of TDCs Deposited by PS-PVD Method

The paper presents an advanced technology of Thermal Barrier Coatings (TBCs) deposition called Plasma Spray – Physical Vapor Deposition (PS-PVD). The PS-PVD is a low pressure plasma spray technology to deposit coatings out of vapor phase, which enables obtaining of columnar ceramic coatings. In this paper, the influence of various gas mixtures on properties of deposited coatings has been investigated. The measurement of coating thickness was conducted by a light microscopy method, followed by a statistical analysis. All processes had been conducted at a very low feed rate, which additionally affected ceramic microstructure.

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 Effect of Long-Term Annealing on Microstructure of Aluminide Coatings Deposited on MAR M200 Superalloy by CVD Method

The paper presents the influence of long-term heat treatment on aluminide coating. The MAR M-200 nickel superalloy was use as base material. The aluminide coating was deposited in low-activity chemical vapour deposition process using Ion Bond BPX Pro 325s device with following parameters: temperature 1040°C, time 12 hours, pressure 150 mbar. The samples (14 mm diameter) were annealed at 1020°C in vacuum for 12, 16 and 20 hours respectively. The XRD phase analysis and SEM microstructural observation with EDS analysis were conducted. The phase composition analysis showed that after deposition the NiAl phase is a main component of the coating. After the 20-hour-long annealing presence of Ni3Al phase in the coating was observed. Changes in structure of coatings and Al content during heat treatment were detected as well. The maximum duration of heat treatment performed for Ni superalloy with aluminide coating without significant changes in coating phase composition and microstructure is 16 hours.

Microstructure of Thermal Barrier Coatings (TBC's) Obtained by Using Plasma Spraying and VPA Methods

Thermal Barrier Coatings are the main type of coatings used for protecting turbine blade surfaces and the surface of modern jet engines combustion chamber parts. Depending on the type of engine element, the coatings are produced as plasma-sprayed MeCrAlY bond-coats with a ceramic outer layer or as Pt-modified aluminide coatings with a ceramic EB-PVD-deposited layer. Currently, research is being conducted on the deposition of a new type of coatings consisting of bond-coats with mulitlayer structure. In the article, the results of the study on the obtainment of TBCs with multilayer structure are presented. To obtain the metallic bond-coat, the process of atmospheric plasma spraying and the out of pack aluminizing (VPA) method were combined. The coatings were deposited on the surface of Rene 80 nickel superalloy. The first layer of the coating was a plasma-sprayed MCrAlY bond-coat, on which a diffusion aluminide layer was deposited with out of pack method. On the bond-coat, a standard ceramic zirconium oxide (ZrO2*20Y2O3) layer was deposited. The microstructure analysis, was conducted, using light and SEM microscopy. The phase and chemical composition analyses were done using EDS and XRD methods.

The Influence of Process Parameters on Structure of Ceramic Coatings Deposited by PS-PVD Method

Thermal Barrier Coatings (TBC) is the most advanced system for protection of turbine blades and vanes against high temperature, and oxidation. They are used in most advanced jet engines. In present article the new Plasma Spray Physical Vapour Deposition Technology was used to obtain yttria stabilized zirconia oxide coating with columnar structure. In research the different process parameters were changed. It was observed that powder feed rate had big influence on coating thickness. The large amount of Ar in plasma gasses combined with high powder feed rate resulted in partial evaporation of ceramic powder and splat-type structure. The same effect was observed when the power current was decreased form 2400 to 1600 A as well as pressure was increased to 200 Pa when the powder feed rate was 30 g/min. The obtained results showed that full evaporation of ceramic powder requires very low feed rate of ceramic material (2 g/min), high power current and high He content into plasma.