OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 6 No. 3 2024 Introduction The relevance of the use of additive technologies in the manufacture of electrodes for electrical discharge machining (EDM) has arisen due to the increased requirements for the accuracy and quality of manufacturing of complex-profile products [1–3]. It has been established that one of the most rational additive methods for producing tool electrodes (TE) is the technology of selective laser melting (SLM) [4–8]. It is noted that the use of additive technologies allows to provide the required parameters of repeatable geometry of complex-profile elements, as well as to provide increased performance and durability of TE through the use of new compositions of powder materials. In the works [9–13] the efficiency of composite tool electrodes obtained using additive technologies is noted. The principle of SLM technology is to split the product into layers and then print the product with cyclic repetition of operations. Increased requirements to accuracy, quality and reliability of product manufacturing require the use of high-quality TE repeating the surface profile. The required dimensional accuracy of products machined by the EDM method varies from 12 to 6 grades of accuracy, and the required roughness in terms of Ra from 3.2 to 0.8 μm. Increased requirements of accuracy and roughness are connected with operational peculiarities; machined surfaces are in conjunction with kinematic units and mechanisms. The works [14–18] consider the SLM method for the production of metal tool electrodes. The authors note that the use of additive technologies for growing TE allows not only to provide the required parameters of repeatable geometry of complex-profile elements of products, but also to obtain increased performance and durability of TE by using new powder materials. The main parameters of the SLM process are laser power, scanning speed, hatch type and distance, layer thickness and powder characteristics. These parameters affect the formation of defects in the process of TE growing. Porosity is the most frequent and difficult defect to eliminate in selective laser melting. Pore formation is influenced by the properties of the initial powder material, machine parameters and growth modes [19–21]. Another defect arising in the application of powder additive technologies is nonfusion, which occurs when single tracks do not overlap sufficiently with each other. Incorrectly selected modes for a certain material lead to increased porosity. At insufficient power value in the SLS process, the powder layer is not completely melted, which leads to the effect of spheroidization or non-melting with the previous layer due to the presence of unmelted particles in the track [22]. Increasing the power value leads to intensive evaporation of the material or the most fusible components of the powder, this contributes to the formation of pores. The presence of such defects contributes to the intensification of TE destruction in the EDM process. Also the presence of instability in the TE structure can negatively affect the formation of a stable spark formation process during copy-piercing machining, which will negatively affect the quality of processing. At present, the formed approaches to the design of TE configuration and assignment of machining modes rely on the methods of design of loaded critical products. These approaches do not include the peculiarities of the physical side of the EDM process. It is necessary to optimize the dimensions and shape of TE not only taking into account mass and mechanical characteristics, but also taking into account its physical properties (electrical resistance and the possibility of forming a stable spark generation channel). Initial parameters of TE influence the formed surface and directly the TE flow rate. Structural defects intensify the process of TE consumption in the process of EDM. The required surface quality is affected by the roughness of the TE not only before EDM, but also in the process itself. On this basis, it is established that ensuring the requirements of the TE quality is an urgent scientific and technological task. The purpose of the work is an experimental study of the application peculiarities of additively manufactured TE in the copy-piercing EDM of critical products. Objectives of the study are as follows: 1) to develop a rational technique for manufacturing tool electrodes from maraging steel MS1 using the selective laser melting method. These tool electrodes should have a minimum number of structural defects for further copy-piercing EDM; 2) to establish an empirical dependence of the surface quality parameter of the additively manufactured TE from maraging steel MS1 depending on the modes of copy-piercing EDM;
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