INVESTIGATION OF THE HEREDITARY EFFECT OF THE STRUCTURE OF THE INITIAL METAL-POWDER COMPOSITION AND THE PARAMETERS OF LASER SURFACING ON THE QUALITY OF DEPOSITED LAYERS OF EP648 ALLOY

The results of studies of the chemical and granulometric composition of metal powder compositions of the EP648 brand (CrNi 50WoMoTiAlNb), fraction 40 ‒ 150 microns, obtained by gas atomization (MPC 1) and centrifugal plasma spraying (MPC 2), the particle size of the powders was determined by dry sieving according to GOST 18318 ‒ 94, the fluidity of the powders was checked in accordance with GOST 20899 ‒ 98. using a calibrated funnel (Hall device), the bulk density is in accordance with GOST 19440 ‒ 94. According to research, both batches of compositions comply with the regulatory documentation TU 78-265 ‒ 2023 in their parameters. Direct laser surfacing was carried out at a running energy of 60 J/mm and 70 J/mm on plates made of CrNi68WoMoTiAlCo-VD (EP693) grade material on an ILIST-XL technological laser growing unit using the studied metal-powder compositions, the surfacing modes were selected according to previous studies. In the samples deposited from composition 1, multiple pores (0.06 ‒ 0.08 mm) were found, as well as hot crystallization cracks 0.3 ‒ 0.6 mm long, extending along the boundary of columnar crystals. No defects were found in the samples deposited from composition 2. The main parameters of metal-powder compositions affecting the formation of structural defects in the deposited material are investigated. The main defects of the initial metal-powder compositions that have a negative hereditary effect on the quality of the deposited material have been identified: the presence of satellites (small particles connected to larger ones) and pores on the surface of the powder particles, which is directly related to the method of their preparation. The effect of linear energy on the residual porosity of the deposited material has been established.

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