# Comparison of the Wear of Toroidal and Spherical Cutters in Milling and the Impact of Corrosion
## 1 Introduction  
Tool wear is a common phenomenon in the machining process, which directly affects machining accuracy, quality, efficiency, and economic efficiency. Monitoring tool wear can enhance finishing process efficiency, reduce machining costs, and yield positive economic benefits. Most publications in the field discuss the experimental analysis of the wear mechanism on the ball end milling cutter [1]. In their work, [PERSON] et al. [2] experimentally performed the machining of hardened 1.2379 (X1655 CrCoMo12) steel (S8 HRC) using a spherical cutter to identify tool durability and appropriate machining parameters, based on the analysis of edge wear patterns. They concluded that the cutting, adhesion, and positioning mechanisms are all responsible for tool wear [2]. Tool wear is a continuous process and influences the dynamics of machining. Increasing cutting speed leads to increased abrasive wear, which becomes as dominant as chemical wear [3]. The increase in wear on the edge causes an intense increase in frictional forces, which leads to an increase in cutting force [4]. Extreme machining conditions that generate high temperatures at the interface between the tool and the workpiece can significantly accelerate tool wear [5]. The intensity of tool wear, in addition to its direct influence on the surface processing time, also influences the roughness of the machined surface [6, 7, 8, 9, 10, 11]. A few specialized studies have established the relationship between cutting regimes and tool wear in relation to changes in surface quality [12, 13, 14, 15, 16, 17, 18], but those publications have not mentioned the production area with the applicability of toroidal milling cutters and spherical cutters. [PERSON] argues that regular milling puts a lot of pressure on the tooth and the protective layer of the tool, so the cemented carbide and the coppering layer must be chosen carefully, because poor resistance can destroy the edges of the tool. The coating almost perfectly holds the processed material from sticking, but its durability to wear and adhesion to the base can be improved by adjustments to the machining strategy [19]. A very important factor in the process of milling a complex surface with a ball end milling cutter is the selection of the machining strategy and the angle of inclination [20]. These parameters have a significant impact on machining time, surface quality, and tool wear [21]. According to the findings in [22], the inclination angle of the machined surface, \(\alpha=0\), should be avoided, because in this case, the cutting speed is equal to 0. [PERSON] and [PERSON] [23] used ball end mills at different tilt angles to study tool durability and quality of machined parts and concluded that machining at a tool tilt in the range of 10-20\({}^{\circ}\) is the optimal machining for fast milling in the mold manufacturing industry [23]. [PERSON] and [PERSON] argue that tool geometry has a significant influence on the processing of CFRP materials. This study focused on investigating the effect of tool angle of action on wear, cutting forces, roughness of the machined edge, and delamination in non-contiguous milling of CFRP laminates [24]. Tool wear is commonly associated with mechanical processes that contribute to the gradual degradation of the tool; however, the influence of chemical factors should not be overlooked. Corrosive effects play a significant role in determining a tool steel's resistance to corrosion-related wear. Over time, and depending on environmental conditions, virtually all metals are subject to corrosion to varying degrees. Tool steels are a large group of non-alloy and alloy steels that are used in the formation of various materials in engineering, their most important feature being their durability. It is intended that the material from which the tool is made has a good resistance to wear, considering all the processes and stages that a tool goes through with various factors, including physicochemical factors. In most cases, the wear process is due to several factors combined.