MACHERENA - New Tools and Processes for Improving Machining of Heat-Resistant Alloys Used in Aerospace Applications
Overview
Background & policy context:
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.
Objectives:
The partners of this project wanted 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, and
- improvement of finishing quality.
All these objectives were 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;
- 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.
Methodology:
The project objectives were 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 collaborated with the R&D centres, and the tools and coating producers, in defining which machining processes and tools were used to evaluate the new developments. Three demonstrators (one from each material family) were defined, as they were 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 were evaluated, taking into account that these tools will be coated.
New nanocomposite coatings were developed, considering the special requirements specified by the end-users and machining shops. There were mainly three lines of the research. The system AlTiSiN was be optimised to cope with the demands of hardness and friction. An approach was also made to other compositions, where the Ti was substituted by other elements that had shown better friction behaviour, or where low-friction phases were added.
The developed nanocomposite coatings were tested in the laboratory facilities. The coatings were 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 were investigated. The tools were also analysed to determine the failure modes, and this analysis acted as input for coating optimisation. At this point, optical microscopes, scanning electron microscopes (SEM), profilometry and roughness measurement devices, and metallography facilities were used. Furthermore, advanced machining processes, like high pressure cooling machining, were tested on the coated tools to increase even more efficiency (tool lifetime, machining speed, etc). The tests started with the Fe-Ni and the Ni alloys, and further addressed the machining process for the g-TiAl intermetallic.
The third leg of the testing table consisted of real production tests performed at the machining shops. The results of these tests provided feedback and helped the optimisation of both coatings and machining parameters. The results were evaluated in the production of real parts (demonstrators), one of each from the material families selected.
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