United Kingdom Atomic Energy Authority

David S Rickerby

Joseph P Coad

Richard Stuart Nelson

John Cook

Derek S Whitmell

Clive F Knights

Philip Warrington

Silicon carbide filaments are coated to protect them from attack by a titanium matrix material when incorporating them into a metal matrix composite. The coating method comprises coating the filaments firstly with a carbon layer and then with a titanium carbide or boride layer whose carbon or boron content decreases progressively from its interface with the carbon layer to its exterior surface. A layer of titanium or a titanium based alloy may be provided on the titanium carbide or boride layer to facilitate incorporation into a metal matrix. Preferably, the layers are applied by sputter ion plating.

Silicon carbide filaments bearing a carbon layer and a titanium carbide

An apparatus for coating by sputter ion plating comprises a chamber having a gas inlet and outlet for passing gas under low pressure continuously therethrough; a cathode fabricated of coating material or precursor therefor positioned in the chamber; and means for generating a glow discharge within the chamber to sputter cathode material to form a coating thereof or of a product obtained therefrom on a substrate also positioned in the chamber. The cathode includes a plurality of projections (e.g. fins) extending from a surface, their disposition and geometry being such as to increase the effective ion current density in the chamber. In this way, high currents at low voltages and pressures may be achieved so that the apparatus can be used to coat a large substrate load, possibly at a higher coating rate.

Coating apparatus

A coating is formed on a substrate by sputter ion plating wherein a DC glow discharge is generated under soft vacuum conditions in the presence of the substrate and of a cathode constituted by the coating material thereby to release material at the cathode by ion bombardment, which released material diffuses to the substrate to form the coating thereon, and wherein a potential is applied to the substrate during coating. In order to control the coating, for example when it is an alloy containing Al and when the substrate has sharp edges, the potential is applied in the form of an AC bias of e.g. 20 to 200 volts wherein ion polishing occurs in the negative part of the cycle and retention of coating material in the positive part thereof.

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Jesmond, United Kingdom

David S Rickerby