# Assessment of the Functional Properties of the Surfaces of Ductile Cast Iron Parts
## 1 Introduction
[PERSON] and [PERSON] [26] showed that feed rate is the most influential parameter on surface quality, as observed for EN-GJS-500-7 ductile cast iron [1]. Studying the material characteristics and microstructure is also considered as a way to understand how the material behaves during machining. For example, [PERSON] et al. [27] explored the effect of the microstructure of ductile iron on machinability. [PERSON] et al. [28], on the other hand, considered cutting forces in addition to the effect of microstructure. Due to the ambiguity in determining the machinability of the material resulting from changes in the periodic cutting speed with the progress of the machining product, the second of the basic machinability indices, i.e., roughness, is a better criterion for its assessment. Roughness, unlike the periodic cutting speed, is a quantity bound by and defined in the product design documentation (and/or process documentation). Therefore, its limit value should be respected, as well as other parameters related to the geometrical accuracy of the product [29; 30; 31]. The value of the chosen roughness index is usually expressed by numbers, which is an absolute value for comparison [32; 33; 34]. This is regardless of the fact that roughness is usually assessed in alternative ways, i.e., as good (below the acceptance level of the selected index value) and as bad (above the acceptance level of the selected index value) [35]. Research on the relationship between machinability and surface roughness of cast iron parts has been carried out in several works. [PERSON] et al. [19] examined the machinability of EN-GJS-600-3 ductile cast iron from the point of view of the relationship between material microstructure and surface roughness. They showed that when machining settings are constant, there is a relationship between microstructure and surface quality. [PERSON] et al. [36] investigated the flank wear and surface roughness when machining gray cast iron with mixed ceramic tools. They found that the flank wear largely increased with cutting speed, while feed rate had the greatest effect on surface roughness. [PERSON] and [PERSON] [37] studied the evolution of surface roughness and mixed ceramic tool life during dry and compressed air-lubricated machining of gray cast iron. They found that for speeds higher than 400 m/min and compared to dry machining, compressed air machining provided good surface quality and increased tool life. [PERSON] and [PERSON] [38] examined the surface roughness and cutting forces generated when turning two white cast irons of different hardness with cubic boron nitride and ceramic tools. The results showed that feed rate was the main parameter affecting surface roughness, while depth of cut had the greatest effect on cutting force. They also described the application of the Taguchi method to determine the optimum surface roughness in turning high-alloy white cast iron [39]. [PERSON] et al. [40] investigated the effect of cutting parameters on surface roughness when machining gray cast iron with carbide tools and concluded that surface roughness mainly depends on the feed rate and the cutting radius. [PERSON] et al. [41] studied the wear evolution of carbide-cutting tools when turning gray cast iron. The results of their analysis showed that the cutting speed had the greatest influence on the flank wear of the tools. [PERSON] et al. [42] presented a comparative study of both surface roughness and tangential cutting force obtained when machining EN-GJL-250 cast iron [43] with uncoated and coated silicon nitride ceramics. Better surface quality and lower cutting force were obtained with the coated ceramic tool than those achieved by the uncoated ceramic. The review has shown that, to date, the literature provides little information related to changes in machinability and the influence of technological machining parameters on the formation of surface geometrical texture indices related to their functionality in the case of parts made of EN-GJS-600-3 ductile cast iron.