2.2.5. Tool Wear Analysis

After being used for machining the workpiece, the tool wear sustained by the machining tools was assessed by performing SEM analysis, identifying the main wear mechanisms as well as performing wear measurements on the tools' top views (flank wear, VB), more precisely, VB3 according to the standard ISO 8688-2:1986 [42]. This was performed in this way due to the selected machining parameters. In fact, these caused primarily localized flank wear near the tools' chamfer. EDS analyses were also carried out during tool wear assessment to characterize phenomena related to material adhesion to the tools' surfaces. The tools' rake and clearance faces were also analyzed, characterizing and comparing the sustained wear for all tested tools. Furthermore, the amount of lost tool material was assessed by comparing the change in tool geometry with that of a tool that had not been used for machining (new tool). In Figure 1, the reference for tool tooth/face identification is displayed, showing the top view of an unused end-mill, as well as the scheme used for measurement according to the standard [42].

**Figure 1.** Reference used for tool wear evaluation during SEM analysis (**a**); types of wear on endmilling cutters according to ISO 8688-2:1989 (en) (**b**) [42].

As seen in Figure 1a, the numbers depicted are used to identify the tools' rake face (RF) and clearance face (CF). As mentioned, the numbers refer to the tools' teeth. Additionally, as three tools per test condition were used, an identification number ranging from 01 to 03 was added to the end of each image reference. As previously mentioned, the selected machining parameters caused a high amount of localized flank wear (VB3) and, as such, the tool wear was assessed according to the standard [42]. The wear measurements were performed in "Position 1", depicted in Figure 1b.

After each machining test, every tool was subjected to a preparation procedure to enable its analysis using the SEM equipment; this procedure was performed as described in Section 2.2.1.
