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1

Influence of air plasma spraying process parameters on the thermal barrier coating deposited with micro- and nanopowders

Kubaszek Tadeusz, Góral Marek, Pędrak Paweł

Materials Science Poland

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2022

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Vol. 40, No. 3

80--92

EN

This study investigates the optimal conditions to deposit a thermal barrier coating using micro- and nanopowders in the air plasma spraying (APS) process. The influence of the APS process parameters on the thickness, porosity and hardness of the yttria-stabilized zirconia (YSZ; ZrO2 × 8Y2O3) coatings deposited with a single-electrode plasma gun was determined. The temperature and velocity of melted particles were determined by the DPV diagnostic system to decrease the number of experimental processes. The current and H2 flow rate were changed in this research. Metco-6700 YSZ micropowder has already been used in plasma spray physical vapor deposition. The results of this study suggest the possibility of using it for APS. The particles of this powder are characterized by high temperature (2,700°C–2,900°C) and high speed (>380 m/s). The highest thickness of the coating was obtained with 6 NLPM (normal liter per minute) H2flow and 800 A current. Difficulties were observed with the feeding of the powder particles at higher H2flow. The results showed that using APS, deposition of Metco-6609, a nanopowder normally used in suspension plasma spraying, is possible. In this research, this powder was fed using a carrier gas. The coatings were around 40 μm thick and had high porosity. The lowest porosity of the coating was obtained at a current of 600 A and H2 flow rate of 12 NLPM. In the coatings, unmelted spherical particles were also visible.

2

Effect of Isothermal Treatment on Ni3Al Coatings Deposited by Air Plasma Spraying System

Mehmood K., Rafiq M. A., Durrani Y. A., Khan A. N.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 1

277--283

EN

Ni3Al coatings were obtained on AISI 321 steel samples by air plasma spraying system. The behavior of heat treatment on intermetallic coatings were evaluated after exposure at various temperatures i.e. 500ºC to 800ºC. The stay time in this regard was varied from 10 to 100 hours. The coatings were then characterized by X-Ray diffraction analysis, optical and scanning electron microscopy, eddy current measurements and stress analysis. It was observed that the formation of NiO increases drastically with time and temperature. The hardness of the coating increases with the formation of NiO. It was noted that the residual stresses can be correlated with the formation of NiO. Further, the development of residual stresses can be monitored by a non-destructive technique i.e. eddy current method.

3

The porosity assessment of ceramic topcoat in thermal barrier coatings deposited by APS method

Pytel M., Góral M., Nowotnik A.

Advances in Manufacturing Science and Technology

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2016

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Vol. 40, nr 2

53--65

EN

In the paper the comparison of open porosity measurement results of ceramic topcoats in thermal barrier coatings (TBCs) was presented. TBCs were produced by Air Plasma Spraying (APS) method and were consisted of two coatings – an outer ceramic topcoat and metallic MeCrAlY bond coat deposited onto surface of René80 Ni-based superalloy. For deposition of ceramic coatings Metco 201 B NS, Metco 204 NS and Metco 210 powders were used whereas for deposition of metallic bond coat AMDRY 365-1 MeCrAlY powder was used. Both types of coatings were deposited using Thermico A60 plasma gun. The microstructure investigations of cross-sections of produced TBC’s were carried out using Hitachi S-3400N scanning electron microscope. Qualitative image analysis of microstructure of produced TBCs as well as analysis of percentage of pores surface area content AA was performed. The evaluation of porosity in ceramic topcoat was carried out by image analysis using MeTilo v.12.1 quantitative software.

PL

W pracy przedstawiono analizę wyników badań porowatości otwartej w zewnętrznej warstwie ceramicznej powłokowej bariery cieplnej TBC. Międzywarstwę metaliczną wytworzono przy użyciu proszku AMDRY 365-1, natomiast warstwę ceramiczną przy zastosowaniu proszku Metco 201 B NS, Metco 204 NS i Metco 210 firmy Oerlikon Metco. Warstwy natryskiwano za pomocą jednoelektrodowego palnika plazmowego A60 firmy Thermico, w warunkach ciśnienia atmosferycznego (APS) na podłożu nadstopu niklu René 80. Badania mikroskopowe powłokowych barier cieplnych TBC prowadzono przy użyciu skaningowego mikroskopu elektronowego Hitachi S-3400N. Wykonano analizę jakościową obrazów mikrostruktury oraz określono pole powierzchni przekroju płaskiego porów otwartych. W ocenie porowatości zewnętrznej warstwy ceramicznej stosowano program komputerowy do ilościowej analizy obrazu MeTilo v.12.1.

4

Thermal barrier ZrO2 - Y2O3 obtained by plasma spraying method and laser melting

Kobylańska-Szkaradek K.

Archives of Materials Science and Engineering

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2009

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Vol. 36, nr 1

12-19

EN

Purpose: The aim of the paper is to determine the influence of laser melting upon the selected physical properties of ZrO2 - Y2O3 ceramic coatings deposited by APS (Air Plasma Spraying) method on super-alloys which function as TBC (Thermal Barriers Coatings). Design/methodology/approach: Laser melting which helps eliminate pores and other structural defects of coatings deposited by plasma spraying method should contribute to the improvement of their density and durability as thermal barriers. In order to prove the assumptions made in the paper, coatings featuring varied porosity and deposited upon the nickel base super-alloys surface with the initially sprayed NiCrAlY bond coat have been subjected to laser melting and then their structure, thermal conductivity and thermal life prediction in the conditions of cyclic temperature changes from 20 to 1200°C have been examined. Findings: It has been revealed that the coatings featuring low porosity laser melted on part of their thickness and heated up to about 700°C demonstrate the highest thermal life prediction under the conditions mentioned and at slightly lower thermal conductivity. Heating is intended to lower the structural stresses which are connected with the change of ceramic volume at crystallization as well as thermal stresses resulting from varied expansion of coating and metal substrate. Research limitations/implications: Low wettability of metal by ceramic which results from various surface tensions of these materials is the cause of their lower adhesion to the substrate during laser melting all through their thickness. It is so because delaminations occur between phases the boundary and cracks. Practical implications: The worked out conditions of laser melting might be used in the process of creation of ZrO2 - Y2O3 coats which feature high working durability upon super-alloy elements. Originality/value: It has been found that homogenization of chemical composition of coatings occurs during laser melting leading to the reduction of ZrO2 - Y2O3 phase with monoclinic lattice participation as well as to the reduction of structural stresses which accompany this phase transformation during heating and cooling process.

5

Thermal barrier ZrO2-Y2O3 obtained by plasma spraying method and laser melting

Kobylańska-Szkaradek K.

Journal of Achievements in Materials and Manufacturing Engineering

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2006

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Vol. 17, nr 1-2

77--80

EN

Purpose: Purpose: The aim of the paper is to determine the influence of laser melting upon the selected physical properties of ZrO2 - Y2O3 ceramic coatings deposited by APS (Air Plasma Spraying) method on super-alloys which function as TBC (Thermal Barriers Coatings). Design/methodology/approach: Laser melting which helps eliminate pores and other structural defects of coatings should contribute to the improvement of their density and durability as thermal barriers. In order to prove the assumptions made in the paper, coatings featuring varied porosity and deposited upon the nickel base super-alloys surface with the initially sprayed NiCrAlY bond coat have been subjected to laser melting and then their structure, thermal conductivity and thermal life prediction in the conditions of cyclic temperature changes from 20 to 1200oC have been examined. Findings: It has been revealed that the coatings featuring low porosity laser melted on part of their thickness and heated up to about 700oC demonstrate the highest thermal life prediction under the conditions mentioned and at slightly lower thermal conductivity. Research limitations/implications: Low wettability of metal by ceramic which results from various surface tensions of these materials is the cause of their lower adhesion to the substrate during laser melting all through their thickness. It is so because delaminations occur between phases the boundary and cracks. Practical implications: The worked out conditions of laser melting might be used in the process of creation of TBC which feature high working durability upon super-alloy elements. Originality/value: It has been found that homogenization of chemical composition of coatings occurs during laser melting leading to the reduction of ZrO2 - Y2O3 phase with monoclinic lattice participation as well as to the reduction of structural stresses which accompany this phase transformation during heating and cooling process.