Variation of Grain Size in Vapor Deposited Titanium Coatings on Beryllium Substrates

摘要

The increase in grain size (to a final constant value) during deposition is a well known occurrence in physical vapor deposition. Columnar grain structures result as the coating thickens beyond the point of constant grain size (in general, for those thicknesses greater than approximately 25 mu m). As the deposition is taking place, the grain size of the Ti coating increases from that on the order of 0.01 mu m to that greater than 1.0 mu m. At a certain critical thickness during deposition, t/sub c/, the grain size stabilizes. In this study, the minimum coating thickness required to produce the ultimate grain size is sought. The effect of coating texture and deposition conditions on coating to substrate bond strength has been established in earlier work. Purpose of this investigation is then to relate the critical thickness to achieve a stable grain size with the texture of the coating. The distribution of grain size within the coating may provide a qualitative characterization of the stress relief driven growth in grain size which produces enhanced bonding of the Ti coating to its Be substrate. (ERA citation 11:051284)