Structural and mechanical properties of stainless steel formed under conditions of layer-by-layer fusion of a wire by an electron beam

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 23 No. 4 2021 aqueous suspension of chrome oxide. The microstructure was controlled after etching of the microsection. The section was etched by the solution of concentrated nitric ( HNO 3 ) and hydrochloric ( HCL ) acids at a volumetric ratio of 1:3. XRD analysis was aimed at determining the parameters of elementary cells of compositions and phase composition with the help of a Shimadzu XRD-7000S X-ray diffractometer located in the Scienti fi c and educational innovative center “Nanomaterials and Nanotechnologies” at Tomsk Polytechnic University (School of Advanced Manufacturing Technologies) at an accelerating voltage and current of 40.0 kV and 30.0 mA, respectively. The source of X-ray Cu K α radiation (wavelength of 1.5406 Å) was Cu anode. The measurement range was from 10 to 80 degrees, the scanning speed was 2.0 deg/min with a step of 0.02 degrees. The structural state was identi fi ed by the Rietveld method. The benchmark lattices were represented by the crystallographic data from COD database. The hardness distribution along the specimen height was recorded using an automatic complex based on a Duramin - 5 microhardness meter at indentation load of 25 grams (245.17 mN) and a spacing of 250 μ m from the lower edge of the specimen and between the indentations. The hardness testing along the blank height was performed on a NanoIndenter G200 setup (Materials Science Division, School of Advanced Manufacturing Technologies, NR TPU). The specimen was indented by a Berkovich pyramid at constant load, scheme and spacing between the indentations. The largest load reached 250 mN with a spacing between the sections of 100 μ m and with a spacing from the substrate of 50 μ m to eliminate edge effects of hardness measurement. The mechanical compression tests were performed on an Instron testing rig in accordance with GOST 25.503-97. The load was applied to the longest side of the specimens with a rate of 5 mm/min. During the tests, AISI 308LSi specimens did not fail; the deformation was primarily plastic. Results and Discussion In this work, a batch of specimens was manufactured on an electron-beam 3D-printer [16] developed and produced at Tomsk Polytechnic University. The specimens were studied by several methods (metallographic, tomographic, XRD analysis, etc.). Computer tomography with a resolution of 11.3 μ m has demonstrated no micro- and macro-defects on the surface and in the bulk of the specimen (Fig. 2). This result testi fi es to avoided occurrence of extended defects due to the use of electron-beam-assisted WAAM . Fig. 2. Tomography of AISI 308LSi specimens manufactured by WAAM