OBRABOTKAMETALLOV Vol. 24 No. 4 2022 technology Ta b l e 2 Chemical composition of 3Cr2W8V steel, wt. % C Si Mn W V Cr Ni P S Cu 0.3–0.4 0.15–0.4 0.15–0.4 8.5–10.0 0.3–0.6 2.2–2.7 < 0.35 ≤ 0.03 ≤ 0.03 ≤ 0.03 Metallographic analysis was performed on an optical microscope “METAM RV-34” with a digital camera “Altami Studio”. The stress state of boride coatings after CTT was measured using an installation for determining residual stresses UDION-2 (Fig. 2), developed at IRNTU [23–27]. Elementary strip samples were cut from the initial plate samples on the Discotom-10 cutting machine (Struers, Denmark) using an abrasive disc cutting wheel with the use of abundant cooling (Fig. 3, a). The strips were cut in a mutually perpendicular direction along the X and Z axes (Fig. 3, b), the nominal length of the strips was 60 mm, width – 8 mm. After cutting out the strip samples, its geometric parameters (width b and thickness h), bend of deflection and initial mass were measured. This data is necessary for the subsequent calculation of the TRS. The sample strips were mounted in the devices of the UDION2 installation and its electrochemical etching (anodic dissolution) was carried out in the electrolyte of composition No. 3 (Table 4) with simultaneous recording of the real time sample deformation. After etching, the samples were dismounted and re-weighed; the average etching rate was determined by formula (1). The final stage was the calculation of the TRS in the XUdion software [28] and the construction of TRS distribution plots. Results and discussions The problem of research of TRS by mechanical method Let us denote the problems associated with the measurement of residual stresses by the mechanical method after strengthening thermal and chemical treatment. The determination of TRS by the mechanical method at the UDION-2 installation [23–28] is associated with the registration of elementary samples-strips motion (when measuring residual stresses in plates) during the removal of stressed layers of the material Fig. 2. Installation for measuring residual stresses by mechanical method (UDION-2) a b Fig. 3. Cutting elementary samples-strips from initial plates
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