3.5.4. T4—Wear Mechanism Analysis

T4 tools exhibited the best wear performance of all the tools, exhibiting the lowest flank wear value, especially for high feed conditions. However, these tools suffered considerable damage to their rake faces. Regarding the wear mechanisms identified on these tools, all the previously mentioned were present, especially abrasive wear, coating delamination and material adhesion to the tools' surfaces. The process of coating delamination was the same as identified in the previously analyzed tools, as can be seen in Figure 17.

**Figure 17.** Adhesive wear detected on the T4 tool's rake face, tested at 4-m cutting length and at 100% feed rate.

The substrate's machining grooves, originated from the substrate's grinding process, promoted material adhesion on the tool's surface, thus promoting abrasion and coating delamination on these areas. This was a common trend throughout all the analyzed tools.

The wear sustained by the tools tested at 4 m of cutting length was more severe than that presented by the tools tested at 2 m, with this being a clear factor on wear mechanisms, such as adhesion, at lower feed rates. For higher feed rates, adhesion was identified, but in a smaller amount than that registered at lower feed rates. There was clear evidence of abrasion being the dominant wear mechanism for this tool at a 125% feed rate. Evidence of abrasion at a high feed rate can be observed in Figure 18.

There was no evidence of cracks detected in the analysis of this coating; also, it exhibited the least amount of flank wear for higher and lower feed rates. However, these tools sustained some wear on the rake faces, which can be attributed to chip formation and removal, and the material adhering to the rake faces being pushed upward, promoting adhesion to the tools' surfaces. As seen in all the previously presented tools, this adhesion promoted the delamination of the coating, resulting in the high wear of the rake faces.
