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New Tools and Processes for Improving Machining of Heat-Resistant Alloys Used in Aerospace Applications


A286 and INCONEL 718 are materials that, due to their high Ni content and heat resistance, are very difficult to machine, and this results in the high cost of parts manufactured with these materials. The results of this process will open the way for more cost-effective production processes for aerospace parts. TiAl is a good candidate material for future aerospace applications, due to its low weight and good resistance at high temperatures. However, its low machinability (10% of that of Ni alloys) makes the production costs very high for many applications. A reduction of the TiAl intermetallic machining cost will open up the possibility of the design and application of new parts.

Project objectives

The partners of this project want to develop new machining tools, nanocomposite coatings and machining processes to address the following industrial objectives:

  • tool life increase
  • reduction of production costs
  • increase of machining productivity (more advanced cutting parameters)
  • optimal coolant utilisation
  • improvement of finishing quality.

All these objectives are related to the machining processes of heat resistant alloys used in aerospace applications. The selection of materials will be focused on the following:

  • Fe-Ni alloys: A286
  • Ni based materials: INCONEL 718, IN 100
  • Intermetallics: g-TiAl

Description of the work

The project objectives will be addressed by the development of new tool geometries, hard and low-friction nanocomposite coatings produced by physical vapour deposition (PVD) methods and new machining processes (high pressure cooling). At a first stage, the machining shops and end-users will collaborate with the R&D centres, and the tools and coating producers, in defining which machining processes and tools will be used to evaluate the new developments. Three demonstrators (one from each material family) will be defined, as they will be used at the end of the project to evaluate the performance of the new tools, coatings and machining processes. With the defined characteristics of the tools and their problems, the possibility of addressing new tool designs will be evaluated, taking into account that these tools will be coated.

New nanocomposite coatings will be developed, considering the special requirements specified by the end-users and machining shops. There will be mainly three lines of the research. The system AlTiSiN will be optimised to cope with the demands of hardness and friction. An approach will also be made to other compositions, where the Ti will be substituted by other elements that have shown better friction behaviour, or where low-friction phases are added.

The developed nanocomposite coatings will be tested in the laboratory facilities. The coatings will be applied on standard and newly developed tools, and the machining parameters that show the best behaviour of the tool from an efficiency point of view will be investigated. The tools will also be analysed to determine the failure modes, and this analysis will act as input for coating optimisation. At this point, optical microscopes, scanning electron microscopes (SEM), profilometry and roughness measurement devices, and metallography facilities will be used. Furthermore, advanced machining processes, like high pressure cooling machining, will be tested on the coated tools to increase even more efficiency (tool lifetime, machining speed, etc). The tests will start with the Fe-Ni and the Ni alloys, and will further address the machining process for the g-TiAl intermetallic.

The third leg of the testing table will consist of real production tests performed at the machining shops. The results of these tests will provide feedback and help the optimisation of both coatings and machining parameters. The results will be evaluated in the production of real parts (demonstrators), one of each from the material families selected.

Expected results

  • Reduction by more than 50% of the process costs where the tools have been coated and new cutting technologies have been applied.
  • Increase by more than 100% in machining efficiency of milling Fe-Ni, Ni alloys and g-TiAl
  • Increase by more than 100% in machining efficiency of turning Fe-Ni, Ni alloys and g-TiAl
  • Increase by more than 50% in machining efficiency of drilling Fe-Ni, Ni alloys and g-TiAl

The term ‘machining efficiency’ is directly related to production costs, and takes into account parameters such as tool life, machining speed and tool cost.