Vacuum Deposition of Thick Coatings and Free-Standing Parts Using Electron-Beam Evaporation

Abstract

Continued improvements in electron-beam evaporation technology have led to applications for vacuum deposition to apply thick coatings and to fabricate free-standing parts. The use of improved electron-beam guns, rod-type source feeders, high-capacity power supplies, and beam-sweep control components has permitted high-quality thick coatings and shapes to be continuously deposited in thicknesses from 0.010 in. to more than 0.100 in. The deposition of three materials using electron-beam heated sources is described. The materials are: magnesium, as a subliming material; gold, as an evaporating metallic element; and Type 304 stainless steel, as an alloy. Descriptions of the electron-beam equipment, the materials handling, the vacuum systems, the tooling, and rate monitors are presented, together with a discussion of the continuous-deposition process techniques. Evaporation–deposition parameters for the various materials and typical conditions for the film depositions are reported. Measurements were made to determine deposition rates at various electron-beam power levels for all of the deposited materials. The effects of the substrate temperature and the deposition rate on the deposited films were investigated and data are presented showing at several temperatures and rates. Metallographic analyses and mechanical property measurements are discussed showing the variation in coating characteristics as a function of the deposition conditions. A discussion of alloy deposition is included with a description of techniques used to deposit a specific alloy (Type 304 stainless steel) as an example of alloy deposition. A description is given of the equipment and process control used to deposit thick stainless-steel parts. Metallographic and chemical analyses of these deposits are reported, including the variations in alloy composition as a function of film thickness.