OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 6 4 3) to establish an empirical dependence of the wear of the additively manufactured TE from maraging steel MS1 depending on the modes of copy-piercing EDM; 4) to assess the effect of the modes of copy-piercing EDM on the surface quality of the additively manufactured TE from maraging steel MS1. Research methodology The research was carried out on the basis of the center of collective use “Center of additive technologies” of the Federal State Educational Institution of Higher Professional Education “Perm National Research Polytechnic University”. Manufacturing of TE prototype was carried out by the additive technology method (SLM). Tool electrodes were made of MS1 maraging steel powder. The powder particles had an average size of 20–40 μm and were spherical. Maraging steel are unique low-carbon martensitic steels that gain strength from intermetallic precipitates formed during the aging heat treatment process. Low carbon content provides good weldability, and significant alloying additives allow achieving high strength due to precipitation hardening mechanism. The following defects occur during the SLS process: cracks, pores, rather rough surface with the presence of melted powder particles. It is necessary to work out fusion modes on this MS1 powder. Carrying out trial modes will allow obtaining TE with a minimum number of defects. The fusion modes were studied using the Realizer 50 machine (Fig. 3a). This machine operates according to the SLM technology. It is used primarily for producing small-sized parts from various powders. The machine has a pulsed fiber laser. This laser has the ability to adjust the beam trajectory, as well as the duration of illumination. One of the main advantages of the Realizer SLM 50 is the high level of detail in the products. Argon was used as a protective gas for sintering. Four modes (Table 1) of fusion of MS1 powder material were used to obtain TE and the best quality one was selected. Ta b l e 1 Technological modes of manufacturing the tool electrode No. t, μs I, mA S, μm Pav, W Filling step, μm h, μm V, m/s 1 40 1,400 20 35 0.05 30 1 2 40 1,400 30 35 0.05 30 0.75 3 20 1,200 20 30 0.05 30 1 4 20 1,400 20 35 0.05 30 1 The parameters varied during manufacturing of TE from the powder of MS1 maraging steel by SLM method were exposure time for each point t, μs; operating current I, mA; distance between points of the laser trajectory S, μm; average power of laser radiation Рav, W; filling step, μm; thickness of a single layer h, μm; scanning speed V, m/s. The samples of tool electrodes were made in the form of parallelepipeds with a length of 30 mm and a cross section of 5×5 mm. Fig. 1 shows the obtained samples on the growth substrate. The high energy density of the SLM process leads to excessive material evaporation and spattering, resulting in the formation of a large number of pores. The pores reduce the fatigue characteristics and mechanical properties of the resulting products by acting as stress concentrators. Cracks on the surface of the products obtained by SLM methods are caused by a large temperature gradient be- Fig. 1. Samples of tool electrodes
RkJQdWJsaXNoZXIy MTk0ODM1