Matthieu Cavellier's PhD Thesis

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The aim of this work was to evaluate the possibilities of the miniaturized nitrogen ion implantation process "Hardion+" developed by Quertech Ingénierie, for surface treatment of pure magnesium, pure copper, brass and bronze.

Thanks to this new process, we were able to create magnesium nitride in pure magnesium, which induced an increase in surface hardness. Even though the same process was used, it was impossible to create any metal nitride into pure copper or copper alloys.
Nevertheless, we observed an enhancement of surface properties: ball-on-disk tests highlighted that friction coefficient and wear rate decreased due nitrogen implantation, and different kinds of corrosion tests performed on copper and brass revealed that corrosion resistance in salt solution can be increased. Nanoindentation tests proved that surface hardness of bronze was multiplied by four after nitrogen implantation.
Various nitrogen implantation doses were tested on copper, brass and bronze and the results showed that an optimal dose inducing the most significant enhancement can be found. However, this optimal dose can be different according to the property targeted, and in some cases, a small variation around this optimal dose can be sufficient to loose these remarkable properties.
Although the implanted layer thickness is below 500 nm, some macroscopic and long-range effects can be observed, such as the creation of a diffusion barrier by nitrogen implantation into copper. The advantages of this new property are already used for treatment of spot welding electrodes, and makes people from connector industry thinking about all the possibilities of "Hardion+" process.

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