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New thermochemical treatment using pressure support to increase lifetime and reliability of forming tools and mechanical components

Tool wear has a critical influence on lifetime and reliability. One of the main ways to reduce the deterioration process of forming tools and mechanical components is to improve surface characteristics through hardening treatment such as nitriding/nitrocarburizing. At present, a large variety of nitriding processes are performed in industrial applications. Nitriding enhances wear resistance and fatigue life of the machine parts and tools. Each nitriding technique has its own specific advantage and disadvantage. For example, conventional nitriding of surface contaminated materials or chromium steels with thin passive layers may be problematic. Consequently, complex and expensive pretreatments are necessary. Ion nitriding processes partially solve the problems. Nevertheless, this last technique presents other inconveniences because of the necessity to generate an electrical field surrounding the pieces, mainly when the geometry of the pieces is complicated (holes, grooves, sharp edges) or when the positioning of the pieces into the furnace is important. In general, ion nitriding techniques are very geometry sensitive, and specific knowledge and expertise regarding process required plasma is requested to control the process.

High pressure nitriding is a new technology, existing several prototype furnaces (manufactured by ALD), which can resolve all these above mentioned problems.

The most important advantages of the processes with pressure support, which have been demonstrated during the project, are the following:

- The rapid depassivation of the surface causes a quicker build-up of an enclosed nitride layer and thus shortens treating times.
- High alloyed materials and titanium alloys can also be easily nitrided.
- The precleaning of the parts can be limited to a minimum.
- The results are not geometry-related.
- A specific layer structure is possible by optimization of the process. It has been demonstrated that with high pressure nitriding process it is possible to obtain compound layer, almost, ?-monophase without to introduce carbon gas on high alloys steels (i.e. AISI H13). This monophase layer shows good toughness properties. This result is very interesting industrially.
- High repeatability of results.

Several standard processes have been developed in the project to apply in real parts by the industrial partners.

Reported by

Fundación Tekniker
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