OBRABOTKAMETALLOV technology Vol. 24 No. 4 2022 Ta b l e 4 Electrolyte compositions; parameters, and results of electrochemical etching (anodic dissolution) of samples after CTT Composition No. Electrolyte composition t, oC Current density j, A/dm2 Voltage U, V ÒÐ V , mm/min Comments 1 (%weight.): KNO3 – 12; NaF – 2; NaCl – 1; H2O – rest 30 75 5 0.0062 The surface is dark gray, smooth, even in the center, with a slight undulation along the edges (Fig. 6, a) 2 (%weight.): H3PO4 – 49,5; Н2SO4 – 40; H2O – rest 32 100 8.5 0.007 Textured light surface with metallic luster, case of electrolytic polishing (Fig. 6, b) 3 (g/l): NaNO3 – 60; NaNO2 – 5; Na2CO3 – 5; C3H8O3 – 15; H2O – rest 30 100 10 0.0056 The surface is dark gray, matte smooth, smooth with a few minor micro-steps (Fig. 6, c) Composition No. 1 (see Table 4) [30], recommended for dimensional electrochemical machining of tool steels, generally showed good results, except for a slight surface waviness (Fig. 6, a). Composition No. 2 [29] gives a shiny, though textured, smooth surface (Fig. 6, b), but only for this type of steel. Composition No. 3 recommended for abrasiveelectrochemical machining of metals [33] showed good results, the surfaces of the samples are matte smooth gray with minimal roughness (Fig. 6, c). Preparatory studies have shown that for the layer-bylayer removal of material in the study of TRS by mechanical method in samples after diffusion boroaluminizing, the most acceptable results are obtained by the process of anodic dissolution. It should be noted that in each specific case, the selection of the electrolyte composition and the necessary electrical and temperature conditions is carried out individually for each material, taking into account the type of its treatment; this procedure is time-consuming and requires test samples for testing the process. In these studies, the composition of electrolyte No. 3 for anodic dissolution showed the best result (Table 4). This electrolyte also showed good results with anodic dissolution of the surface layer of 5CrNiMo steel samples after CTT. To control the process of anodic dissolution of the material, in particular, to establish its required speed, adjustment of the electrolyte temperature and electrical parameters of the process (voltage, anode current density) can be applied. Fig. 5. Electrochemical cell for testing the process of anodic dissolution: 1 – cathode (lead plate); 2 – anode (sample); 3 – beaker with electrolyte solution
RkJQdWJsaXNoZXIy MTk0ODM1