Alumina film sputter deposition on mold steel by large-area electron beam irradiation

During the large-area EB irradiation, plasma generation is confirmed by collision of electrons with vaporized workpiece materials above the substrate surface due to its high energy density. This phenomenon would cause the sputtering of target material when it is set near the substrate surface. Thus, there is a possibility for coating a target material on the substrate surface by the large-area EB irradiation. The simultaneous sputter deposition of target material with melting and resolidification of workpiece surface by the large-area EB would improve the adhesion strength between the coated film and the workpiece surface. In this study, a new ceramics coating method with sputtering of target tube by large-area EB irradiation is proposed. Ceramic target tube made of alumina is put on the substrate surface of mold steel, and the large-area EB is irradiated to the substrate surface. The alumina film with thickness of several micro meter can be formed on the substrate surface. Moreover, the film formation mechanism is discussed by changing material property of a jig supporting the alumina target tube. The spectrum of plasma generated on the substrate surface during the EB irradiation is also analyzed. It is made clear that the magnetic property of jig greatly influences on the film formation. Furthermore, main components of plasma generated on workpiece surface during the process are components of steel in the case of low number of EB irradiation, while much more alumina component as a film is detected in the case of high number of EB irradiation.