The sputter deposition and evaluation of tungsten and chromium for use in weapon components. Technical report

This work was conducted to establish sputter deposition as a candidate production coating process for military items. Specifically two areas were evaluated -- deposition on internal bore surfaces of gun barrels and deposition of wear resistant coatings on external surfaces. The feasibility of sputter deposition on bore surfaces of 7.62mm gun tubes was studied using both a modified dc-triode scheme with tungsten targets centered on the gun tube axis and a dc-diode scheme with the plasma supported by thermally emitted electrons from a hot target/filament centered on the gun tube axis. Although the latter scheme gave better deposition characteristics, further refinements appear necessary before the method can be adapted as a production coating process. High quality chromium coatings were produced on 7076-T6 aluminum substrates in the work involving deposition on external surfaces. The wear test results indicate the sputter deposited chromium coatings exhibited superior substrate adherence and more uniform wear characteristics when compared to the electro-deposited chromium plating. (Author) (GRA)