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Fracture behavior in Amorphous and Ceramic Coatings on Aluminum Alloy Substrate

Published online by Cambridge University Press:  21 February 2011

J. Kameda
Affiliation:
Ames Laboratory, Metallurgy and Ceramics Division, Ames, IA 50011
R. Ranjan
Affiliation:
KOMAG Inc., 275 South Hillview Drive, Milpitas, CA 95035
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Abstract

Fracture behavior in Ni-10 wt.%P amorphous (10 µm thick) and overlay Y2O3 stabilized ZrO2 (0-1.0 µm thick) ceramic coatings on Al alloy substrates has been investigated using small punch (SP) testing and acoustic emission (AE) techniques. SP tests showed that coating cracks extensively propagate along both the radial and tangential directions under the biaxial stress condition. The formation of cracks was more profoundly found in Ni-P amorphous coatings than in amorphous/ceramic coatings. The cumulative AE events were well correlated with the severity of coating cracking independent of the type of coatings. Ceramic coatings with a thickness of 0.25 and 1.0 µm led to a decrease in the fracture toughness by 15–20%, compared with a uncoated alloy. The coating effect on the fracture toughness is discussed in light of residual stresses induced during coating processing and the presence of coating cracks.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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