# Wear Behavior of Uncoated and Coated Tools in Milling Operations of AMPCO (Cu-Be) Alloy
## 4 Conclusions  
In this study, a comparison of uncoated and CrN/DLC multilayered coated tool performance in the machining of a copper-beryllium alloy was made. Various machining tests were performed, evaluating the influence of both cutting length and feed rate on the tools' wear behavior and produced machined quality. The following conclusions can be drawn:  
* Regarding the surface roughness of the machined part, it was clearly noticed that the feed rate had a high influence on this parameter, with values of surface roughness increasing by up to four times from the feed rate of 750 mm/min to 1500 mm/min. This was registered for both uncoated and coated tools; however, the coated tools produced better results for cutting lengths of up to 36 m, with surface quality deterioration from that point onward. The uncoated tools produced an overall better surface quality for the maximum cutting length of 48 m.
* The tool's wear behavior was similar with an increase in the feed rate values, with the sustained flank wear being more severe for a feed rate value of 1500 mm/min. A flank wear of 80.71 mm and 102.3 mm was registered for uncoated and coated tools, respectively. These maximum flank wear values were registered for higher cutting lengths, with the coated tools experiencing considerably more wear for higher cutting lengths than the uncoated tools. However, for cutting lengths of 18 and 36 m, these tools exhibited less wear than the uncoated ones. Thus, it seems that the 36-m cutting length represents a turning point for the tools' wear behavior. For the 48-m cutting length, the uncoated tools presented a better behavior than the coated ones, thus, the improved behavior of the coated tools ends at about a cutting length of 36 m.
* Regarding the tool wear mechanisms, it was possible to observe that the main wear mechanisms were adhesion, tool chipping, and abrasion. In addition to these, coating delamination was registered in the coated tools. Tool chipping and cutting-edge breakage was more prominent for higher values of feed rate, and was registered in both coated and uncoated tools. Both the coated and uncoated tools presented similar wear behaviors, with the coated tools exhibiting less wear and producing a better machined quality in the beginning of the tests. However, for longer cutting lengths the coated tools were outperformed by the uncoated ones, producing a worse surface finish and suffering more wear. This indicated that this coating was not best suited for finishing operations of copper-beryllium alloys, following the described machining strategy. The development of different machining strategies for finishing can prove beneficial for the optimization of the wear behavior of these tools, a subject that can be explored in future work. It was also found that feed rate has a very high influence on the produced machining quality, with lower feed rates producing the lowest surface roughness values. Preliminary tests carried out at a feed rate value of 350 mm/min produced highly satisfactory values, for both coated and uncoated tools, with the values obtained from each of the tool types being very similar; however, in this case, the uncoated tool outperformed the coated tool for every cutting length value, i.e., it produced an overall better surface finish. By lowering the feed rate, it is possible to skip additional steps that are required to produce mold parts, such as grinding and polishing operations, which are very usual regarding molds for shiny surfaces. This opens a new avenue of future study regarding the influence of feed-rate on the machining of these alloys, and how this can contribute for the optimization of the processing of copper-beryllium alloys. Regarding the study of this lower feed-rate, more intermediate stages should be inserted, accompanied by an analysis of the wear of both tools throughout the test. Furthermore, other machining parameters (such as cutting speed and even different lubrication conditions) and strategy influences on the surface roughness could be evaluated.