# Comparison of the Wear of Toroidal and Spherical Cutters in Milling and the Impact of Corrosion
## 1 Introduction
For example, mechanical wear is often accompanied by corrosive wear, resulting in what is referred to as mechanical-corrosive wear [25; 26; 27]. It is important to identify the elementary processes of tool wear, as this allows for a better prediction of the service life of the tool, as well as making their service life more efficient [27]. The evolution of the wear of the ball end mill is divided into three stages these being the initial stage, the intermediate wear stage, and the late wear stage. In the intermediate wear phase, the reworked layer becomes smoother, which increases the contact area and reduces the pressure on the surface, thus reducing the wear rate, mainly due to the formation of crescent-shaped pits. In the advanced wear stage, the quality of the powder of the ball end cutter deteriorates rapidly, generating pronounced burs at the margins, which significantly accelerate wear. At this stage, profile breakage, fragment detachment, and micro-cracking occur, leading to tool failure [28]. I agree with what the author says above, but is there not an intermediate stage before late wear? The visible effects of wear can be damage to the edge surface of the tool and changes in the shape of its geometry, and these cause qualitative changes in the characteristics of the machined surface over time. As a result, the life of the tool is negatively affected by the intensity of the working conditions, but also by the corrosion of the working environment [26]. It is important to monitor tool wear and keep tools in good condition to avoid non-compliant surface processing. Wear is caused by both thermal and mechanical forces, which can be mitigated by operating with proper operating parameters and with the proper trajectory to spread wear along the entire length of the edge. While each tool will eventually have some sort of wear, the effects can be delayed by paying close attention to the cutting speed, feed on the tooth, and the angle of inclination of the tool's axis relative to what is normal on the surface. Once tool wear occurs, the protective corrosion-resistant layer is removed, exposing the worn area to further corrosion. This paper addresses a detailed scientific analysis of milling tool wear, focusing on the comparison between three toroidal milling cutters and three spherical milling cutters used in machining a total of 45 complex surfaces with each tool. To ensure a rigorous and replicable evaluation, the machining regimes (feed rate, depth of cut, and feed) were kept constant, varying only in the angle of inclination of the tool. This variable parameter makes it possible to isolate the influence of tool geometry and angle of inclination on wear, making it easier to determine its minimum and maximum values. The main objective of the study is to quantify and compare the wear values for the two types of milling cutters, highlighting the differences in their performance and durability under surface processing conditions with complex geometries. In addition, the paper extends the investigation into the long-term effects of corrosion on the analyzed tools. Based on the measurements made five years ago, following initial processing, new measurements will be made on the worn surfaces of the tools, which in the meantime have been exposed exclusively to ambient conditions without being reused. This stage of the study aims to evaluate corrosion-induced changes. The choice of the five-year period for storage, although seemingly arbitrary, reflects a realistic range in which corrosion can significantly affect worn surfaces and in which special tools, stored for future applications, could be reused. The results of this analysis will provide essential information on the impact of corrosion on the functional integrity of tools and the feasibility of their reuse. This study contributes to optimizing tool selection by application and developing maintenance and storage strategies, reducing the costs associated with premature tool replacement and improving the sustainability of manufacturing processes.