One of the most critical operations when manufacturing a turbine disc is the broaching process of mounting grooves in the shape of a “Fir Tree” or “Dove Tail”. This groove has very high requirements for precision and surface integrity. It is the geometry in charge of ensuring the fastening of the blades located on the periphery of the disc, which work in a high range of operating temperatures and at more than 60,000 revolutions per minute. As is customary for turbine components, broaching operations are carried out on nickel and cobalt-based superalloys, heat-resistant alloys capable of maintaining their mechanical properties at high temperatures. This present very low machinability, adding an extra complexity to the process.
The CFAA has a vertical broaching machine (EKIN A218) designed as a test bench with the capacity to introduce specimens in the shape of a ring or disc of 500mm in diameter. It supports a maximum broaching effort of 70kN, reaching a maximum speed in finishing operations of 40m/min. It has a single broach holder suitable for the installation of a set of brushes up to 2640mm in length.
The test bench is designed to carry out research in two fundamental lines. In the first place, development of new qualities, geometries and conditions for cutting brushes. Second, the broaching of new materials in the research phase; that is, key materials for the design of the new high-speed turbines. At this point, compliance with the strict geometric and surface requirements of the final component is pursued.