When industrial parts such as gears are machined[1] at very high speed, the absence of cutting fluid (for economic and ecological reasons) leads to an increase in temperature at the material/mill interface, which can reach 800-1000°C. In order to increase the service life of the hobs, which are repeatedly used through multiple regrinding/decoating/surface preparation/recoating operations, the surface of the cutting tool is covered with a very hard coating. This very thin coating, with a thickness of 1 to 5 µm (micron), must have a high resistance to temperature, abrasion and impact, a low chemical affinity with the materials to be machined, optimised chip evacuation, etc.

The TINALTA[2] project, obtained by Stéphane LUCAS and led by Emile HAYE, is financed thanks to the Win²Wal programme of the SPW-EER, and involves the Laboratory of Analysis by Nuclear Reactions (LARN) of the Department of Physics of UNamur (NISM Institute) and the spin-off Innovative Coating Solutions (ICS). The aim is to propose a product/process combination that allows the coating of machining tools with an optimised, high-performance trimetallic nitride, in particular with a very high service life.  This coating is currently being qualified and validated on an industrial scale. It still needs to prove various indicators and pass a reliability study at high production rates.

  1. Machining is a generic term that includes a whole series of operations such as turning, milling, drilling, etc.
  2. TINALTA: Product/Process combination allowing the coating of machining tools with an optimised metal nitride

"The coating is deposited by PVD (Physical Vapor Deposition). This vacuum deposition method is based on plasma processes," explains Emile Haye, post-doctoral researcher in charge of the project at UNamur. "A plasma is an ionised gas obtained when a voltage is applied between two surfaces in a vacuum, in the presence of a small quantity of gas. It is the same principle as neon, except that by modulating the electrical parameters, it is possible to 'spray' a source of material, which then condenses on the opposing surfaces. This method of coating synthesis has the advantage of requiring no solvents and no additional steps. The energy balance of this process is therefore low," he continues.

Emile HAYE

Among a series of constraints specific to the deposition of this coating, it is important that it can be removed. Once the tool has been used, it is re-sharpened. The coating is then removed and the surface repaired before a new coating is applied. Thus, the tool can be reused several times (up to 10-12 times). This reconditioning of industrial tools is justified for tools with high added value (hobs, gear tools), because of their very high price.

Within the framework of the TINALTA project, we have developed an innovative process, based on PVD methods, with an original coating composition. This was made possible by pooling the ICS and LARN expertise.

ICS

An application for a European patent has just been filed and there are many prospects for development. We'll show you in pictures!

The project partners

Project funding: Win²Wal programme of the RW, agreement 1910092.