Investigation and application of EB-PVD and related processes for high-rate deposition of aluminum alloys

Abstract

Electron beam physical vapor deposition (EB-PVD) with high power axial EB guns has high deposition rates and therefore is well suited for depositing comparatively thick coatings with high throughput in mass production processes. The top sliding layer on bearing shells is a well-known use case for this technology. In low-cost manufacturing, often semi-finished products such as sheets or strips are coated, from which final products with a broad range of dimensions can be manufactured.The adaptation of related processes such as pretreatment and substrate cooling of three different semi-finished products was the focus of the investigations. All process steps were optimized for high throughput. Deposition with AlSn or AlSnCu alloys was carried out at coating rates up to 1 μm/s. These alloys, containing elements with different vapor pressures, were evaporated out of one continuously fed crucible with long-term stability.The deposited coatings have finely dispersed tin clusters in the aluminum matrix. The tin clusters have linear dimensions in the range of 200 to 400 nm. This size range is a direct consequence of the high coating rate; it is thus process-specific for EB-PVD. Such coatings are highly beneficial for applications such as plain bearings. Initial load tests have impressively confirmed the advantages for EB-PVD processed bearings.