B. C. Wu - Storming Media

Zirconia/Pack-Aluminized Co-29Cr-6Al-1Y Thermal Barrier Coatings

Authors: S. F. Chang; C. H. Chao; B. C. Wu; R. Q. Leu; E. Chang; NATIONAL SUN YAT-SEN UNIV KOOHSLUNG (TAIWAN) INST OF MATERIALS SCIENCE AND E NGINEERING*

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Effects of Bond Coat Pre-aluminizing Treatment on the Properties of ZrO(sub 2)-8wt.%Y(sub 2)O(sub 3)/Co-29Cr-6Al-1Y Thermal Barrier Coatings

20 APR 90

Authors: B. C. Wu; C. H. Chao; E. Chang; T. C. Chang

Zirconia-8wt.%-yttria/aluminized Co-29Cr-6Al-1Y thermal barrier coatings (TBCs) were tested in the temperature range from 1000 to 1150 C. In this study an as-sprayed Co-29Cr-6Al-1Y bond coat was aluminized by a pack cementation process to effect an aluminum-rich outer layer consisting mainly of a CoAl phase before subsequent overlaying of a zirconia-8wt.%-yttria top coat. As a result, the high temperature oxidation resistance of a conventional vacuum plasma-sprayed Co-29Cr-6Al-1Y bond coat was improved ...

The Oxide Pegging Spalling Mechanism and Spalling Modes of ZrO(sub 2) 8 wt% Y(sub 2)O(sub 3)/Ni-22Cr-10Al-1Y Thermal Barrier Coatings under Various Operating Conditions

FEB 90

Authors: B. C. Wu; E. Chang; C. H. Chao; M. L. Tsai

MAR-M247 superalloy coated with zirconia-8wt.%yttria/Ni-22Cr-10Al-1Y duplex thermal barrier coatings were tested under various operating conditions within the temperature range from 1000 to 1150 C. The spalling modes of the top coat were classified by fractographic observations on all spalled specimens. The postulated degradation mechanism is oxidation of the bond coat, coupled with unrelieved coefficient of thermal expansion mismatch stress caused by the pegging effect of protruded bond-coat out-grown oxides growing ...

Thermal Cyclic Response of Yttria-Stabilized Zirconia/CoNiCrAlY Thermal Barrier Coatings

15 MAY 89

Authors: B. C. Wu; E. Chang; S. F. Chang; C. H. Chao

Thermal cyclic tests of zirconia-8 wt.% yttria/Co-32Ni-21Cr-8Al-0.5Y duplex thermal barrier coatings (TBCs) were conducted from room temperature to 1000, 1025, 1050, 1075 and 1100 C. Failure analyses of all spalled specimens were carried out to elucidate the degradation mechanism of the TBCs. It was found that the decrease in cyclic life of TBCs is most dramatic when the temperature is increased from 1000 to 1025 C. Specimen geometry has a ...

Microstructures, Properties and Failure Analysis of (ZrO(sub 2)-8wt. %Y(sub 2)O(sub 3))/((Co,Ni)-Cr-Al-Y) Thermal Barrier Coatings

MAY 89

Authors: B. C. Wu; E. Chang; D. Tu; S. L. Wang

The microstructures, properties and failure analysis of certain (zirconia-8wt.%yttria)/((Co,Ni)-Cr-Al-Y) thermal barrier coatings (TBCs) were evaluated in relation to the thermal cycling tests at 1050 C. It was found that the overlaying of a top coat thickness of 0.15 mm can substantially decrease the oxidation rate of bond coat when compared with top-coat-free specimen. Also, scanning electron microscopy and electron microprobe analyses of spalled TBCs revealed that irregular aggregates of bond ...