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INNOVATIVE PVD NANO-COATINGS ON TOOLS FOR MACHINING TITANIUM AND NICKEL ALLOYS

Final Report Summary - MATINA (Innovative PVD nano-coatings on tools for machining titanium and nickel alloys)

The aim of this project was the substantial improvement of cutting tools for the machining of nickel and titanium alloys. These alloys present several problems during machining operations, and as a result today there are important restrictions regarding tool performance that limit the economy and quality of the final parts. The most important fact when machining nickel and titanium alloys is the tendency to work harden, due to the localised overheating, and stick or adhere to the cutting tool surface. Therefore, tools with sharp edges, to avoid deforming the material before cutting it, with a very good surface finish and low chemical affinity are required, as any surface defect may cause the material to adhere to the tool.

The application of selected PVD nano-structured coatings with a thickness of less than 1 µm can improve the life of Ni and Ti cutting tools without worsening at all tool sharpness. It will make it possible that the nickel and titanium machining benefit from a technology that has already been successfully applied (micro-coatings) to machining other materials, i.e. steel alloys, but has show little if any improvement in Ni and Ti. A good selection of PVD nano-structured coatings can decrease friction, which will result in a reduction of the overheating risk, allowing higher machining speeds or even avoiding the use of lubricant. Furthermore, a hard nano-structured coating with a nano-thickness (< 1 µm) can be applied to the tool maintaining its surface finishing and sharpness, thus delaying the presence of local wear defects; this will reduce material sticking and increase tool life.

Inasmet has designed new coatings based on CrAlXN where X is a doping element. They have also worked in the development of nano-structured coatings of CrAlZrN, CrAlYN and CrAlBN. Different deposition parameters has been analysed as the influence of the target doping power, process temperature, nitrogen partial pressure. Inasmet has optimised the coating synthesis and has selected the following coatings to be applied on the tools to perform the machining tests.

A PVD coating applied by magnetron sputtering on cutting tools has shown an increase in productivity up to 30 % when machining Ti alloys. This coating is based on CrAlN. The sectors of application are: aeronautical, biomedical, energy, manufacturing.

Fabrication of aircraft components using the newly developed machining processes. The machining procedures used in the project with the selected coatings and tools will be used by the machining workshops to machine similar components in the near future.

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