1. YILDIZ TEKNİK ÜNİVERSİTESİ MAKİNE MÜHENDİSLİĞİ BÖLÜMÜ
HARDNESS AND FRACTURE TOUGHNESS OF ATMOSPHERIC PLASMA SPRAYED YTTRIA-STABLIZED ZIRCONIA THERMAL BARRIER COATINGS
ALI AVCI
AYSEGUL AKDOGAN EKER
Yildiz Technical Universty, Istanbul, 34349, Turkey
International Journal of Arts&Sciences
FREIBURG CONFERENCE
Nov 28-Dec 02, 2016

2. History of TBCs
Firstly, thermal barrier coatings were developed1950s by NASA. These studies aimed to protect from hot effect. After 1970s TBCs were used in gas turbine combustion chamber. In the advancing decedas, Al2O3 , mullites were used as a TBCs however their mismatch between thermal coefficient of expension of metals.

3. abstract
Thermal barrier coatings (TBCs) are commonly used in gas turbines hot section components sach as burners, blades, vanes TBCs protect the substrates and turbine components against to thermal effect and increase turbine efficiency.
It is important to increase toughness and hardness of the TBCs due to hot gasses effect and thermal shock.

4. Why TBCS are Important
Generally, Ceramic coatings on the materials surfaces are economic to protect the materials from corrosion, wear, hot effect etc.
Thanks to surface modification provides needed features morever metalic substrates preserve their toughness, machinability and durabilty etc
TBC consist of three layers;
One of them bond coat,
* to protect metalic substrate from oxidation wear corrosion
* To provide thermal adaptation between substrate and top coat(ceramic)
Other one is ceramic top coat;
* Insulation layer from hot gas or thermal effect
* Wear resistance
Last one is metalic substrate ;
* It can work high temperature almost %90 of melting temperature
* To provide toughness, durabilty and matrix
* Generally super alloys are used as substrate because of ıts hıgh feature such as high melting temp.

5. Demostration of a TBC system which is applied to turbine vane to serve as a thermal insulator

6. Material and methot Using the stainless steel as substrate
NiCrAlY commercial (Amdry 962) powder was deposited on to AISI304 stainless steel substrates as a bond coat using high velocity oxygen and fuel methot (HVOF).
Yttria-stabilized zirconia (YSZ) and Al2O3 coatings composite powders were deposited as a top coat using by atmospheric plasma spray APS on the bond coat

7. Produced steps of TBCs APS Coating System
Scaning electron microscope investigation
Cutting and polishing processes
Micro Vickers methot

8. In the present study,
The coatings toughness and hardness were investigated to be dependent on the Al2O3 rate that affects coating hardness, toughness and microstructural features.
The fracture toughness and hardness was measured using micro Vickers indentation technique and the micro structure was observed to show micro cracks using by (SEM) scanning electron microscopy.

9. Coatings power microstructural
Power material
Chemical Comp.
Grain Shape
Grain Size
Density (g/cm3)
YSZ
ZrO2 8Y2O3
Spheral μm
5,9
Al2O3
2 wt.% SiO2-98 wt.% Al2O3 μm
3,9
Amdry 997
Ni 23Co 20Cr 8.5Al4 Ta 0.6Y μm
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10. Processes parameters of coating
Material
Pressure(bar)
Flow Rate
Processes
AMDRY 997
Oxygen
Propan
Air
Spray Distance (mm)
Power Feed Rate (g/min)
10.3
6.2
7.2 24 40 50
250

11. Sem INVESTIGATION OF COATINGS

13. Vickers Hardness Value
Test was applied randomly 12 differetnt point on the samples by by HVS 1000 micro vickers hardness devices. Load was determined 300 g and loading time was 15 s.
Before the hardness test all sampless polishing test.

14. Hardness Vickers

17. conclusions Adding to AL2O3 is increasing hardness at YSZ
While porosity is getting high the hardness is falling
Vickers hardness values depending on the alumina ratio.. The values is changing between 1032 HV to HV
While hardness is increasing the wear resistance is increasing(as well mechanic strength)
Alumina ratio increase the density , decrease the porosity
Alumina protect to coatings from oxygen attack, corrosiaon and hot gas affect

18. “İstanbul Kalkınma Ajansı tarafından desteklenen Bilimsel Araştırma ve Eğitimde Mobil Laboratuvar ile İleri Karakterizasyon Uygulamaları Projesi kapsamında hazırlanan bu yayının içeriği İstanbul Kalkınma Ajansı veya Kalkınma Bakanlığı’nın görüşlerini yansıtmamakta olup, içerik ile ilgili tek sorumluluk Yararlanıcı’ya aittir”