Purpose. The article is aimed to investigate the structure of the composite coating obtained by pulse-plasma treatment using cathodes of high-carbon material with higher amount of carbide-forming elements. Methodology. The coating was produced using electrothermal axial plasma accelerator with the following operating parameters: voltage applied to the electrodes is 4.0 kV; amplitude of the current is 18 kA; distance between electrodes of about 50 mm. The treatment was carried out according to the scheme: five pulses with electrode of steel T1 + five pulses with electrode of cast iron Cr28Mn3. The pulsed plasma treatment was followed by heat treatment as holding at 950 °C for 2 hours, followed by oil cooling. Optical (Nikon Eclipse L150) and electron (JEOL JSM-6510) microscopy, energy dispersive spectroscopy (X-Act, Oxford Instruments), the microhardness measurement (FM-300 Future-Tech Corp.) were used for microstructure studying. Findings. It is shown that pulsed-plasma treatment using various electrodes resulted in formation of laminated coating «P18 steel/cast iron 230Cr28Mn3» of 110-130 microns thick. The analysis of micro-hardness coating before and after the post-plasma heat treatment is carried out. It is found that quenching resulted in increase of coating microhardness from 4900-7300 МPа tо 10500-13500 МPа (layer “T1”) and 12000-16500 МPа (layer “230Cr28Mn3”). Originality. The distribution of the alloying elements within the coating is studied. The diffusion transition layer having variable tungsten and chromium content was revealed between the layer “T1” and layer “230Cr28Mn3”. It was shown that after plasma deposition an oversaturated solid solution is being formed in the coating. During post-heat treatment it decomposes with the precipitation of 45-70 % carbides of different shape resulting in sharp increase of microhardness. Carbides amount is proportional to content of carbon and carbide-forming elements in the electrode used for certain layer deposition. Practical value. It was shown the possibility of the formation of a composite layered pulsed-plasma coating with variable chemical composition and micro-hardness in cross-section by means of varying the cathode material and by use of post-plasma heat treatment.
COMPOSITE IMPULSED-PLASMA COATING «STEEL T1/CAST IRON CR28MN3»
2017
Article (Journal)
Electronic Resource
Unknown
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