Gas flow sputtering — An approach to coat complex geometries and Non Line of Sight areas

Abstract

Most PVD techniques are limited in coating complex geometries such as turbine blades without additional substrate manipulation. A novel approach to overcome these limits is the innovative gas flow sputtering. This technique combines a hollow cathode glow discharge with an argon gas flow that supports transportation of sputtered material to the substrate. The mixture of gas and sputtered material flows around the contour of the geometry and reaches Non Line of Sight areas. In this investigation different complex geometries such as u-shaped profiles and pipes were coated with pure titanium. The influence of the angle between gas flow direction and substrate surface (incident angle) on coating thickness distribution, microstructure and crystal orientation was examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that a stripe or a pipe placed parallel to the gas flow direction is coated over the whole length. The pipes are coated outside as well as inside. The circumference of a cylinder positioned perpendicular to the gas flow direction is completely covered with material. In all cases the coating thickness varies over the surface, which is caused by the interplay between convection and out-diffusion as the main deposition mechanisms.