Hughes Aircraft Company

Simon K Nieh

Jesse N Matossian

Frans G Krajenbrink

Robert W Schumacher

Wear-resistant titanium nitride coatings onto cast iron and other carbon-containing materials is enhanced by means of a new surface preparation and deposition process. The conventional pre-deposition surface cleaning by Ar.sup.+ ion bombardment is replaced by a hydrogen-ion bombardment process which cleans the substrate surface by chemical reaction with minimal sputtering and simultaneously removes graphite present on the cast iron surface. Removal of the graphite significantly improves the wear resistance of titanium nitride, since the presence of graphite causes initiation of wear at those sites. Hydrogen ion bombardment or electron bombardment may be used to heat the substrate to a chosen temperature. Finally, titanium nitride is deposited by reactive sputtering with simultaneous bombardment of high-flux Ar.sup.+ ions from an independently generated dense plasma. The resulting titanium nitride coating on cast iron evidences superior wear properties and adhesion compared to conventional reactive evaporation deposition techniques for titanium nitride.

Surface preparation and deposition method for titanium nitride onto

Plasma-enhanced magnetron-sputtered deposition (PMD) of materials is employed for low-temperature deposition of hard, wear-resistant thin films, such as metal nitrides, metal carbides, and metal carbo-nitrides, onto large, three-dimensional, irregularly shaped objects (20) without the requirement for substrate manipulation. The deposition is done by using metal sputter targets (18) as the source of the metal and immersing the metal sputter targets in a plasma (16) that is random in direction and fills the deposition chamber (12) by diffusion. The plasma is generated from at least two gases, the first gas comprising an inert gas, such as argon, and the second gas comprising a nitrogen source, such a nitrogen, and/or a carbon source, such as methane. Simultaneous with the deposition, the substrate is bombarded with ions from the plasma by biasing the substrate negative with respect to the plasma to maintain the substrate temperature and control the film microstructure. The substrate, metal targets, and plasma are all electrically decoupled from each other and from walls (14) of the deposition chamber (12), so as to provide independent electrical control of each component. The PMD process is applicable not only to the deposition of hard coatings, but also can be applied to any thin film process such as for electrically and thermally conductive coatings and optical coatings, requiring simultaneous, high-flux, ion-bombardment to control film properties.

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Monrovia, CA, United States of America

Simon K Nieh