2.1.1. Employed Tools

In this work, four tool types were used to machine the DSS alloy. The tools' substrate was cemented carbide WC-Co grade 6110, provided by INOVATOOLS, S.A. (Leiria, Portugal). This cemented carbide grade presented as micro-grain, with a measurement of about 0.3 μm, and used 6% Co (wt.) as a binder. The tools' substrate was ground, yet the patterns left by this process were seen in the tools' surfaces, even after the deposition process. Regarding the tools' dimensions, all the produced tools were 4 mm in diameter and had a total length of 68 mm. As this study aimed to compare the influence of different coatings as well as different tool geometries in the wear mechanism suffered during machining tests, four tools with different geometries were produced and were coated with three different coatings, TiAlN, TiAlSiN and AlCrN. After production, the tools were subjected to an ultrasonic bath using acetone for 10 min; after this first bath, the tools underwent a second one for 5 min. The acetone was changed between the baths. These tools were coated with three types of PVD coatings, the TiAlN, TiAlSiN and AlCrN coatings. This enabled the comparison of the wear behavior and machining performance of these coatings by creating four different tools, as seen in Table 1.

**Tool Ref. Tool Geometry Number of Flutes/Edges Rake Angle Relief Angle** T1 Flat end-mill 2 30◦ 10◦ T2 End-mill with a 45◦ chamfer, 0.08 mm from the cutting edge 4 35◦ <sup>10</sup>◦ T3 Flat end-mill 4 40◦ 5◦ T4 End-mill with a 0.2 mm corner radius 4 35◦ <sup>10</sup>◦

**Table 1.** Tools created for the machining of UNS S32101.

Regarding the deposition of these coatings, CemeCon CC800/9ML PVD unbalanced magnetron sputtering equipment provided with four target holders was used. After the cleaning process, the tools were assembled in a holder and placed inside the equipment. To ensure that the coatings were deposited onto the tools' surfaces as homogenously as possible, the tool holders were rotated at a speed of 1 rpm during the process. The coating process was similar for the TiAlN and TiAlSiN coatings, with the use of four similar targets. In the case of the AlCrN coating, four targets were also used, two being composed of 100% Cr and the other two of 100% Al. These targets were distributed alternately inside the reactor, resulting in the deposition of alternating layers of Cr and Al. Thin, alternating layers of Al and Cr were achieved on the T1 and T3 tools. The set of parameters used for the deposition of the mentioned coatings can be observed in Table 2. During the deposition

of the various tool sets, flat substrates were placed inside the deposition chamber to create a sample that could be used to determine the coatings' mechanical properties.


**Table 2.** TiAlN, TiAlSiN and AlCrN PVD coatings' deposition parameters.

These parameters have been selected based on previous successful experiments carried out in similar substrates. After deposition, all the tools were packed carefully, avoiding the handling of the tools' cutting areas.
