Effect of substrate morphology on the deposition behavior of α-Al2O3 films by room temperature granule spray in vacuum process

Abstract

In this study, we investigated the influence of surface morphology of a hard substrate on the deposition behavior of α-Al2O3 films coated by a granule spray in vacuum (GSV) process at room temperature. Three types of α-Al2O3 films were prepared by chemical vapor deposition (CVD) on a WC-Co base material: (006) textured film with a uniform and small mold-type morphology, (110) and (012) textured films with large grains and a relatively flat morphology, and flat (006) textured film after polishing. These CVD α-Al2O3 films were further coated with nano-grained α-Al2O3 films by the GSV process. The deposition behavior, adhesion strength, and residual surface stress were found to be strongly influenced by the surface morphology of the hard substrate. For the (006) textured CVD α-Al2O3 film with steep crests and troughs on the surface, the GSV α-Al2O3 film was deposited uniformly, possibly because the powder can be directly anchored by the molding effect and subsequent hammering effect. Such different deposition characteristics also led to a variation in the surface residual stress.