OBRABOTKAMETALLOV Vol. 24 No. 4 2022 TECHNOLOGY Composition No. 1 was taken as the initial electrolyte (Table 3) [29], this electrolyte showed a poor result, the surface of the sample was practically not etched. Composition No. 2 was obtained by increasing the concentration of components of composition No. 1 with an increase in the temperature of the solution. Composition No. 3 is a modification of the previous composition with the addition of nitric acid as an oxidizer. Composition No. 4 is focused on chemical dimensional processing of steels [30]. The condition of the samples surface after chemical etching is shown in Figure 4. a b c Fig. 4. The surface of specimens as a result of chemical etching of specimens made of 3Cr2W8V steel after CTT: a – composition No. 2; b – composition No. 3; c – composition No. 4 As can be seen from the experiments, chemical etching does not give acceptable results, therefore, for layer-by-layer removal of material from samples after CTT, it was proposed to use electrochemical etching, in particular anodic dissolution, when studying the TRS at the UDION-2 installation. The removal of the material during electrochemical treatment occurs under the action of an electric current in the electrolyte medium. The electrochemical treatment process is based on the phenomenon of anodic dissolution of metals. Anodic dissolution can take place in electrolytes of different compositions, including non-aggressive ones – aqueous solutions of salts that are cheap and harmless [31, 32] compared to acidic ones. Under the action of an electric current in the electrolyte, the anode material, which is the test sample, dissolves in the form of processing products. The cathode does not wear out, which is one of the positive features of the process. As a result of the reactions, hydrogen is released at the cathode, and precipitation in the form of insoluble metal hydroxide and oxygen occurs at the anode. Insoluble hydroxide clutters up the electrolyte and reduces the productivity of the process. In this regard, it is necessary to make provision for the processes of regeneration and purification of the electrolyte from the reaction products (settling, filtration, decantation). To work out the process, parameters and composition of the electrolyte, a number of studies were conducted on the anodic dissolution of 3Cr2W8V steel samples after CTT (Table 4). For this, an electrochemical cell was placed in the thermostatic bath of the UDION-2 installation (Fig. 5), a lead cathode connected to the negative output of the power source, and a sample anode connected to the positive output of the power source, was placed in the thermostatic bath. As a power source for the electrochemical circuit, a Mastech HY3010 laboratory DC power source was used with output voltage regulation in the range of 0–30 V at an output current of 0–10 A, with the function of a stabilized current source. As in the case of chemical etching during anodic dissolution, the average rate of layers removal was calculated according to the formula (1).
RkJQdWJsaXNoZXIy MTk0ODM1