Session BB2.6

3:45 PM BB2.6
SYSTEMATIC STUDIES OF SPLAT-SUBSTRATE INTERACTIONS BY SCANNING ELECTRON MICROSCOPY. Tomas Chraska, Jerome Birs and Alexander H. King, Department of Materials Science & Engineering, State University of New York, Stony Brook, NY.

The adhesion of thermal sprayed coatings to their substrates is determined by the properties and morphology of the splats which compose the first layer of the coating. Therefore, a detailed study of single splats has been conducted. Molybdenum was sprayed on four different polished substrates (Steel, Copper, Aluminum and Glass) preheated to three different temperatures (room temperature, 200C, 400C). Specimens were examined in plan view and cross section using SEM and the specimen chemistry was determined by EDS. A number of very different morphologies (e.g. pancake- , flower-, crater-like) has been observed depending on the material and temperature of the substrate. Generally, more splats remained on substrates preheated to the highest temperature. Cracks extending from the splat to the glass substrate or deformation of metallic substrates in the direction of impact were observed, but no signs of alloying were detected. Yttrium stabilized zirconia was sprayed on steel with and without single splats of bond coat (NiCrAl), at room temperature. Powders with four different particle sizes were used. Preliminary results indicate that adhesion of YSZ splats to steel without the bond coat is negligible, and the nature of the bond coat effect is demonstrated in our micrographs.Acknowledgement: this work is supported by the National Science Foundation MRSEC grant number DMR 9632570.