# Cutting Speed and Feed Influence on Surface Microhardness of Dry-Turned UNS A97075-T6 Alloy
## 4 Conclusions  
In this work, the cutting speed and feed influence on the microhardness of dry-turned UNS A97075-T6 alloy samples was analyzed. The results were compared with the non-machined samples, before and after a corrosion process, in order to study the possible connection between cutting parameters, microgeometrical deviations, microhardness, and corrosion. The microgeometrical deviations, evaluated through \(Ra\) and \(Rz\), showed a general trend to increase with feed. However, no significant modifications were observed as a function of cutting speed. The natural roughness, induced by the feed, was predominant over the cutting speed thermal effects (such as surface alterations originated by the indirect adhesion tool wear). These observations are in good agreement with previous research regarding parametric analysis on surface roughness for the 7000 aluminum alloys series. In addition, no significant changes in \(Ra\) were observed after corrosion. However, an \(Rz\) increment was observed, regardless of feed and cutting speed. For the highest feed value (0.20 mm/r), this increment was slightly higher. Therefore, feed seemed to be more influent for the highest tested values. Additionally, the dispersion in the results seemed to be higher for \(Ra\). This fact was more evident for \(Rz\). The appearance of surface alterations, due to pitting corrosion, resulted in a higher dispersion of the maximum height of the surface profile (\(Rz\)). This effect was softer for \(Ra\), because it was calculated as an average value of the surface profile deviations. In general, a surface microhardness (\(HV\)) increment was observed in all samples, after machining and before corrosion, regardless of \(v_{c}\) and \(f\). The highest microhardness was obtained for the intermediate cutting speed (60 m/min) and feed (0.10-0.15 mm/r) values. For low feed and cutting speed, mechanical effects predominated over thermal effects. This fact resulted in finer microstructure than in the non-machined part, giving rise to microhardness increments. For the intermediate range of feed and cutting speed, the mechanical effects were stronger. The thermal effects were increased, but not high enough to compensate for the mechanical effects. As a result, the grain microstructure was finer than for low feed and cutting speed. Finally, for the highest cutting speed (80 m/min), the thermal effects were more relevant and compensated for the mechanical effects, increasing the grain size and reducing the microhardness. Therefore, the mechanical effects, produced by feed, should not be neglected against the thermal effects, produced by cutting speed, within the low range of tested cutting speed. A general microhardness reduction was observed in the samples after corrosion. However, a higher dispersion in the results was obtained in a wide range of cutting parameters analyzed, due to the irregularities in the surface produced by pitting corrosion. Therefore, the corrosion process negatively affected microhardness, but it was not possible to establish a direct relationship between cutting parameters, surface roughness, and microhardness after a corrosion process. It is necessary to highlight that previous works in this regard usually focused on high-speed values of cutting speed, typically used on non-hybridized alloy. Under these conditions, the cutting speed is the most relevant cutting parameter and, therefore, thermal effects predominate over the mechanical ones. However, there is a gap in knowledge regarding the analysis of the possible influence of feed when low cutting speeds are used. Hence, this work covers this gap. Finally, it is necessary to point out that this work is framed within a broader research line, currently in development, regarding the analysis of the cutting parameter influence on the surface integrity of UNS A97075 alloy, turned under dry conditions. This research line focuses on analyzing the relationship between cutting parameters, surface topography, and mechanical properties.