Michal Slaný

While the machining of Inconel 718 has been widely studied, its cast counterpart Inconel 713LC remains underexplored, despite its relevance in high-temperature aerospace and energy components. This work presents a comprehensive investigation of dry milling behavior in Inconel 713LC, focusing on the interplay between tool wear, cutting forces, surface integrity, and chip formation across a broad range of cutting parameters. A stable process window was identified: 30–50 m/min cutting speed and 0.045–0.07 mm/tooth feed, where surface roughness remained below Ra 0.6 µm and tool life exceeded 10 min. Outside this window, rapid thermal and mechanical degradation occurred, leading to flank wear beyond the 550 µm limit and unstable chip morphology. The observed trends align with those in Inconel 718, allowing the cautious transfer of established strategies to cast alloys. By quantifying key process–performance relationships and validating predictive models for tool life and cutting forces, this study provides a foundation for optimizing the dry machining of cast superalloys. The results advance sustainable manufacturing practices by reducing reliance on cutting fluids while maintaining surface and dimensional integrity in demanding applications.

High-velocity oxyfuel (HVOF) coatings are used to protect components from corrosion and wear at higher temperatures and from wearing out after a certain period of time. Hence, to enhance the life of components, further recoating is required, but removing the older coating is a challenging task due to its high hardness. Thus, this research work studied the electrolytic dissolution process of removing WC-CoCr 86/10/4 HVOF coatings and found that at a voltage of 3 V, the coating was not removed, but at a slightly higher voltage of 6 V, the coating was removed completely. When the voltage was 12 V, the surface was damaged, and corrosion also occurred. A combination of tartaric acid (C₄H₆O₆), sodium bicarbonate (NaHCO₃), and water was used as an electrolyte. By using a combination of a voltage of 4.5 V, a current of 1.6 A, and an electrode distance of 55 mm, the coating was completely removed after 10 h, with negligible attacks on the base material. Where the corrosion of the base material is unacceptable, voltages in the range of 4 to 6 V are recommended. If parts have coatings on all surfaces, a voltage within the range of 6 to 12 V can be recommended. The coating from tab SB-002JI-5 TOOLOX-11 and hexagonal mandrel SB-00EA-1 160 TIS was also removed successfully.

Dry machining is one of the main ways to reduce the environmental burden of the machining process and reduce the negative effect of the cutting fluid and aerosols on operators. In addition, dry machining can reduce overall machining costs and, in the case of large workpieces, reduce the extra work associated with removing residual cutting fluid from the workpiece and adjacent area. For high-strength structural steel products, it is typical to drill holes with larger diameters of around 20 mm. Therefore, this work is devoted to the investigation of the dry drilling process carried out on a workpiece made of S960QL steel with a helical drill with a diameter of 21 mm. The aim was to find suitable cutting conditions for dry drilling with regard to process stability and workpiece quality. An experiment performed with a coolant served as a comparison base. A dry drilling experiment was performed with cutting speeds from 30 to 70 m·min⁻¹ and feeds from 0.1 to 0.3 mm·rev⁻¹, and with the results of this experiment, the same experiment with flood cooling was performed. During the drilling process, spindle torque values were recorded using the indirect spindle current recording method. The macroscopic chip morphology was studied to understand the cutting process. The chip thickness ratio was measured, as well as the maximum diameter of spiral chips. On the final workpiece, the qualitative and dimensional parameters of the holes were evaluated, such as the diameter, cylindricity and surface roughness, depending on the change in the cutting conditions and cutting environment. Evaluation of the obtained data led to the following conclusions. When drilling the S960QL material, there is only a very small increase in the drilling torque during dry drilling compared to drilling with cutting fluid. The increase in friction demonstrated by the chip thickness coefficient is significant. The influence of the environment on the dimensional accuracy showed a tendency for a slight increase in the holes’ diameters during dry machining. In comparison, the cylindricity of the dry-drilled holes shows a lower deviation than the holes drilled with cutting fluid. The surface roughness of the holes after dry drilling is affected by the increased friction of the outgoing chips, despite the resulting parameters being very good due to the drilling technology standards. This work provides a comprehensive view of the dry drilling process under defined conditions, and the results represent suitable cutting conditions to achieve a stable cutting process and a suitable quality of drilled holes.