The goal of the project is the development and application of highly adherent CVD diamond (in polycrystalline and nanocrystalline NCD- forms) and diamond like carbon (DLC) coatings on compatible Si3N4 materials.
This ceramic presents a close thermal expansion coefficient to that of diamond, reducing the thermal stresses at the interface, promoting high adhesion strength. CVD diamond/Si3N4 and DLC/Si3N4 materials have a high application potential, its use as biomaterial for surgical implants and medical dev ices being emphasized.
The standard artificial joints are constituted by the UHMWPE/metal bio-tribological system that can be advantageously replaced by smooth DLC or NCD/Si3N4 bio-tribosystems.
This is made by coating a bioactive tough ceramic that enters into the bone, with an ultra-hard biocompatible film with outstanding wear and corrosion resistance. The absence of metallic wear eradicates metallosis. Simultaneously, the reduction of UHMWPE wear will diminish the implant failure probability.
Also, the production of diamond/Si3N4 medical devices for odontologic, orthopaedic and surgical uses, anticipates extended lifetime and resistance to sterilisation procedures. Si3N4 samples are diamond coated by both the microwave plasma chemical vapour deposition ( MPCVD) technique for flat specimens and hot filament (HFCVD) method for complex geometries.
The DLC films are grown by DC or RF magnetron sputtering. Further experiments dealing with friction and wear behaviour of CVD diamond aim the development of dry-running machine elements and metalworking tools that require no pollutant lubrication, with evident environmental benefits.
As cutting tools, CVD diamond/Si3N4 inserts are tested in turning operations with real-time acquisition of cutting forces by dynamometry. The cutting of very hard materials hardmetals, like cemented carbides (WC/Co), with CVD diamond coated Si3N4 inserts, is another goal for this new system.