การศึกษาพฤติกรรมของการออกซิเดชั่นและการเกิดสพอลเลชั่นของผิวเคลือบ CoNiCrAIY ที่ผลิตโดยการพ่นเคลือบด้วยเปลวพลาสมาและการพ่นเคลือบด้วยเปลวเพลิงความเร็วสูงที่อุณหภูมิสูง

Study of the Oxidation and Spallation Behaviour of Plasma-Sprayed and HVOF-Sprayed CoNiCrAIY Bondcoat at High Temperature

Name: ธนิต คุ้มปากพิง

Name: Tanit Khumpakping

Organization : มหาวิทยาลัยเทคโนโลยีพระจอมเกล้าธนบุรี

keyword: Thermal Barrier Coating

; oxidation

; Thermal spraying

; Failure analysis

; Spallation

Abstract: Thermal Barrier Coating (TBC), consisting of a ceramic topcoat (ZrO2-Y2O3) and a metallicbondcoat MCrAlY (where M = Ni and/or Co), is applied on to component surfaces to provide athermal barrier and an oxidation resistance for the components in order to protect against hightemperature oxidation. Most applications are used in high temperature sections of gas turbineengine. During service, an Al2O3 scale is formed between the bondcoat and the topcoat, whichprotects the component from further oxidation. If the oxide film does not possess a good structuralstability or does not have a good protective behaviour, it will lead to premature damage or failure ofthe coatings and the components. The thesis investigated the failure of the TBC used on a high pressure turbine blade (HPT) after it has been in 14000 hours service at maximum temperature of about 1200 OC. The result showed that Al depletion had occurred in the bondcoat adjacent to the bondcoat/topcoat interface. The degree of Al depletion varied throughout the TBC on the turbine blade. In the area where Al depletion had not been identified, precipitations of an Al-rich phase were detected. Large amount of the Al was contained within the Al-rich phase, leaving only a small amount of Al in the surrounding matrix. The assumption was made that the Al content in the bondcoat diffuses to form the Al-rich phase, causing the remaining Al to be insufficient to form a protective oxide film between bondcoat/topcoat interface. Therefore, other oxides were formed. The formation of other oxides, their non-protective property such as NiO, CoO and oxide spinels as the bondcoat oxidationproducts would accelerate the failure of TBC due to interconnected porosity and internal oxidewithin the bondcoat are also responsible for the Al diffusion blockage during service. In the secondpart of the thesis, a Design of Experiment was carried out utilising a Full Factorial technique toselect the optimum parameters for air plasma spraying (APS) and high velocity oxy fuel (HVOF)process. The result clearly revealed that the discontinuities within the bondcoat are significantlyinfluenced by the particle size of the coating powder. The oxidation test was then performed byoxidising the TBC samples at 1100 OC in atmospheric furnace. The oxidation result showed that thediscontinuities control characteristic and oxidation behaviour of the thermal-grown oxide layers.The coatings produced by HVOF technique, which have a small amount of porosity and a low oxidecontent will prolong the life of the coating.

มหาวิทยาลัยเทคโนโลยีพระจอมเกล้าธนบุรี

Address: กรุงเทพมหานคร

Email: info.lib@mail.kmutt.ac.th

Name: สุพัฒน์พงษ์ ดำรงรัตน์

Role: อาจารย์ที่ปรึกษา

Created: 2545

Issued: 2005-11-11

Modified: 2559-01-14

วิทยานิพนธ์/Thesis

ISBN: 9749635175

CallNumber: MT185

tha

DegreeName: วิศวกรรมศาสตรมหาบัณฑิต

Level: ปริญญาโท

Descipline: เทคโนโลยีวัสดุ

Grantor: มหาวิทยาลัยเทคโนโลยีพระจอมเกล้าธนบุรี

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