Specimen Current Imaging of Delamination in Ceramic Films on Metal Substrates in the SEM

Abstract

Plasma spraying of yttria-stabilized zirconia on stainless steel substrates generates rapidly solidified thin film discs called splats. Constraint due to adhesion at their interface generates sufficient stresses during cooling from the splat melting to generate extensive cracking. Stress relief by cracking always accompanied by delamination of the thin films at the edges of cracked segments. It is shown here that images obtained in the SEM through amplification of the specimen current signal generate the right contrast for delineating regions of edge delamination in the cracked segments of a splat. Image analysis using this contrast provides a quantitative measure of the extent of delamination at the interface. Greater delamination in the splats formed on cooler substrates. Correlation also indicates complimentary nature of stress relief by delamination and cracking. A detailed analysis including data from solidification and cooling and cracking statistics will give a measure of the adhesion strength at the interface. This technique is a quick method for measuring delamination of microscopic degree in thin insulating films on conducting substrates.