Microstructural evaluation of laser remelted gadolinium zirconate thermal barrier coatings

Mustafa Guven Gok; Gultekin Goller

doi:10.1016/j.surfcoat.2015.06.074

Microstructural evaluation of laser remelted gadolinium zirconate thermal barrier coatings

Mustafa Guven Gok, Gultekin Goller^*

^*Corresponding author for this work

Department of Metallurgical and Materials Engineering

Istanbul Technical University

Research output: Contribution to journal › Article › peer-review

39 Citations (Scopus)

Abstract

Thermal barrier coatings having NiCoCrAlY bond coat and Gd₂Zr₂O₇ top coat were produced utilizing HVOF and APS processes. Then the coatings were subjected to CO₂ continuous wave laser remelting by using different laser parameters. The effect of laser remelting process on the surface roughness, microstructure, grain size, hardness and phase transformation was investigated. The microstructural characterizations showed that a smooth, flat and dense surface having a network of segmented cracks was observed and open porosities were sealed throughout with a thin (~35μm) remelted layer. The surface roughness value decreased from 8.3μm to 2.9μm for as-sprayed and laser remelted specimens respectively. Furthermore, equiaxed and columnar grains that are perpendicular to the surface were formed and the grain sizes decreased from 7.03μm to 3.69μm due to laser process parameters. The hardness value increased from 10.66GPa to 12.73GPa with decreasing grain size. XRD patterns of as-sprayed and laser remelted top coats indicated that the structure of the coating has been changed due to preferred orientation after surface modification by laser remelting.

Original language	English
Pages (from-to)	202-209
Number of pages	8
Journal	Surface and Coatings Technology
Volume	276
DOIs	https://doi.org/10.1016/j.surfcoat.2015.06.074
Publication status	Published - 25 Aug 2015

Bibliographical note

Publisher Copyright:
© 2015 Elsevier B.V..

Funding

This work was supported by the Scientific Research Project Funds of Istanbul Technical University (Project Number: 38102 ) and the Academic Staff Training Program (OYP) of the Council of Higher Education of Turkey . The authors thank Prof. Dr. Yilmaz Taptik, Assoc. Prof. Dr. Ozgul Keles and Hasan Huseyin Sezer for their contributions on thermal spray and characterization processes.

Funders	Funder number
Council of Higher Education of Turkey
Istanbul Teknik Üniversitesi	38102

Keywords

GdZrO
Hardness
Laser remelting
Microstructure
Plasma spraying
Thermal barrier coating

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10.1016/j.surfcoat.2015.06.074

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title = "Microstructural evaluation of laser remelted gadolinium zirconate thermal barrier coatings",

abstract = "Thermal barrier coatings having NiCoCrAlY bond coat and Gd2Zr2O7 top coat were produced utilizing HVOF and APS processes. Then the coatings were subjected to CO2 continuous wave laser remelting by using different laser parameters. The effect of laser remelting process on the surface roughness, microstructure, grain size, hardness and phase transformation was investigated. The microstructural characterizations showed that a smooth, flat and dense surface having a network of segmented cracks was observed and open porosities were sealed throughout with a thin (~35μm) remelted layer. The surface roughness value decreased from 8.3μm to 2.9μm for as-sprayed and laser remelted specimens respectively. Furthermore, equiaxed and columnar grains that are perpendicular to the surface were formed and the grain sizes decreased from 7.03μm to 3.69μm due to laser process parameters. The hardness value increased from 10.66GPa to 12.73GPa with decreasing grain size. XRD patterns of as-sprayed and laser remelted top coats indicated that the structure of the coating has been changed due to preferred orientation after surface modification by laser remelting.",

keywords = "GdZrO, Hardness, Laser remelting, Microstructure, Plasma spraying, Thermal barrier coating",

author = "Gok, {Mustafa Guven} and Gultekin Goller",

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year = "2015",

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doi = "10.1016/j.surfcoat.2015.06.074",

language = "English",

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AU - Goller, Gultekin

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N2 - Thermal barrier coatings having NiCoCrAlY bond coat and Gd2Zr2O7 top coat were produced utilizing HVOF and APS processes. Then the coatings were subjected to CO2 continuous wave laser remelting by using different laser parameters. The effect of laser remelting process on the surface roughness, microstructure, grain size, hardness and phase transformation was investigated. The microstructural characterizations showed that a smooth, flat and dense surface having a network of segmented cracks was observed and open porosities were sealed throughout with a thin (~35μm) remelted layer. The surface roughness value decreased from 8.3μm to 2.9μm for as-sprayed and laser remelted specimens respectively. Furthermore, equiaxed and columnar grains that are perpendicular to the surface were formed and the grain sizes decreased from 7.03μm to 3.69μm due to laser process parameters. The hardness value increased from 10.66GPa to 12.73GPa with decreasing grain size. XRD patterns of as-sprayed and laser remelted top coats indicated that the structure of the coating has been changed due to preferred orientation after surface modification by laser remelting.

AB - Thermal barrier coatings having NiCoCrAlY bond coat and Gd2Zr2O7 top coat were produced utilizing HVOF and APS processes. Then the coatings were subjected to CO2 continuous wave laser remelting by using different laser parameters. The effect of laser remelting process on the surface roughness, microstructure, grain size, hardness and phase transformation was investigated. The microstructural characterizations showed that a smooth, flat and dense surface having a network of segmented cracks was observed and open porosities were sealed throughout with a thin (~35μm) remelted layer. The surface roughness value decreased from 8.3μm to 2.9μm for as-sprayed and laser remelted specimens respectively. Furthermore, equiaxed and columnar grains that are perpendicular to the surface were formed and the grain sizes decreased from 7.03μm to 3.69μm due to laser process parameters. The hardness value increased from 10.66GPa to 12.73GPa with decreasing grain size. XRD patterns of as-sprayed and laser remelted top coats indicated that the structure of the coating has been changed due to preferred orientation after surface modification by laser remelting.

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KW - Hardness

KW - Laser remelting

KW - Microstructure

KW - Plasma spraying

KW - Thermal barrier coating

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Microstructural evaluation of laser remelted gadolinium zirconate thermal barrier coatings

Abstract

Bibliographical note

Funding

Keywords

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