# Assessment of the Functional Properties of the Surfaces of Ductile Cast Iron Parts
## 1 Introduction  
Ductile cast irons, especially cast iron grade EN-GJS-600-3 [1; 2], are particularly popular for production in the engineering, automotive, or machine tool industries [3; 4; 5]. The main advantages of this material are its low price, good castability, and low costs associated with casting preparation. The strength of ductile cast irons is at a level similar to that of typical carbon steel grades [6]. At the same time, almost all ductile cast iron grades are characterised by good machinability [7] and a high vibration damping coefficient [8], which makes them popular for use in the construction of body components (such as hubs, heads, and housings) of equipment operating under highly stressed conditions and equipment exposed to vibration [9; 10] joined to other components by multi-bolted connections [11; 12; 13; 14]. EN-GJS-600-3 ductile cast iron has a hardness between 190 and 270 HBW [15]. However, specific cutting resistance for cast iron is usually slightly lower compared to steel. It mainly depends on the hardness and is usually in the range of 1400 to 1500 N/mm\({}^{2}\). EN-GJS-600-3 ductile cast iron has a fairly high carbon content (about 3.7 \(\pm\) 0.2%) and a relatively high content of hard silicon particles (about 2.7 \(\pm\) 0.4%) against a soft matrix. Thismakes this material extremely 'aggressive' to the cutting tool material. One of the more common recommendations when machining parts from this material is to use tools with cutting inserts of negative geometry to guarantee high tool life (chipping resistance) of the cutting blades [16; 17; 18]. On the other hand, protective coatings based on aluminium oxides and fine-grain carbide cutting inserts are recommended to increase the wear resistance of cutting inserts. In turn, the selection of appropriate technological parameters for cast iron machining is an important practical issue, especially in terms of the requirements for the state of the geometric texture of the surface set by constructors and ensuring high volumetric efficiency and stable machining by technologists [19]. The machinability of cast iron is one of the basic indicators describing its susceptibility to change in volume, shape, and dimensions [19]. Machinability can be expressed directly by values of basic quantities such as periodic cutting speed and roughness. As a rule, an increase in the periodic cutting speed contributes to faster tool wear (due to an increase in cutting resistance and temperature in the cutting zone). Therefore, there is a natural limit to the maximum value of the periodic cutting speed, beyond which it should not be exceeded when following the desire to improve the machinability of the material. Maintaining a balance between machining parameters such as feed rate and turning speed is one technique for addressing machinability issues. [PERSON] et al. [20] conducted simulation and experimental studies to develop a model for estimating surface roughness. They showed that surface roughness increases with increasing feed rate. With respect to spindle speed and feed rate per tooth, [PERSON] et al. [21] adjusted the depths of the cut. To simulate the measured surface roughness, they were able to create a fairly accurate simulation model. In order to obtain a better surface quality within the roughness parameters, some researchers [22; 23; 24; 25; 26] have conducted studies changing the machining parameters. [PERSON] et al. [22] created a regression model and a neural network model to predict surface roughness, which resulted in good agreement with the experiment. Considering the cutting parameters and cutting tool geometry in the model, [PERSON] et al. [23] developed a method to predict further surface quality. By simulating the surface roughness profile, [PERSON] et al. [24] fitted the simulated data to the experiment to obtain a prediction model. [PERSON] et al. created a model consisting of cutting speed, feed rate, and depth of cut to demonstrate the influence of cutting parameters [25].