Preparation of Thick Functionally Graded Layers of Ceramics by Surface Modification of Tantalum and Titanium Using High Temperature Plasma Processing

Surfaces of metals, such as Ta and Ti, have been changed successfully to a new type of ceramic layers having the compositional gradient by means of the plasma processing at high temperature above 900°C. Surfaces of Ta and Ti were transformed to thick layers of ceramics, i.e. TiC, TiN, TaC or TaN components, respectively, by carburizing or nitriding. Resultantly, a Vicker’s hardness of each modified sample surface remarkably increased over 3000 kg/mm2. The density of carbides or nitrides in the modified layer and at the interface was measured to decrease with depth. The width of interface was wide about 7 \\micron, in the case of TiC . Additionally, the irradiation of 20 MeV-electron beam to samples as the pretreatment before the plasma processing was effective to increase the thickness of modified layer.