National Research Nuclear University “MEPhI” (Moscow Engineering Physics Institute), Moscow, Russia:

V. I. Polskiy, Assistant Professor of a Chair of Physical Problems of Materials Science
V. L. Yakushin, Professor of a Chair of Physical Problems of Materials Science
P. S. Dzhumaev, Assistant of a Chair of Physical Problems of Materials Science, e-mail: PSDzhumaev@mephi.ru
V. N. Petrovskiy, Assistant Professor of a Chair of Laser Physics

This study presents the experimental results of the evolution microstructure, elemental composition and surface hardening of aircraft industry titanium alloys VT16 and VT3-1 (ВТ16 and ВТ3-1) processed by laser and high-temperature pulsed plasma flow treatment. Laser treatment was carried out in ML3-06LD (МЛ3-06ЛД) and ML4-1 (МЛ4-1) laser installations, used for automatic processing of materials. ML3-06LD used the focused laser beam emitted by solid-state fiber laser source with maximum continuous output power in the range of 500–700 W with the beam diameter of 20 mm. ML4-1 was used for the point treatment in the argon gas atmosphere with Nd (YAG) pulsed laser beam focused to 100-1000 m spot. Specific power of the pulse changed from 1.5·104 to 5.1·104 W/cm² and 2 ms pulse duration. High-temperature pulsed plasma treatment was carried out, using the Z-pinch type experimental plasma accelerator setup “Desna-M” (“Десна-М”) by helium plasma flows with an energy density up to 100 J/cm2 and pulse duration equal to 15 s. It was found that VT16 laser weld joint processed by ML3-06LD laser device in the argon atmosphere has the scaly surface relief. Significant changes in microhardness across the weld joint from 3500 MPa at the edge to 5300 MPa at the center were observed. There was made a definition, that laser surface processing leads to the hardening of the surface layers up to 1.7 times. Surface processing of laser device ML4-1, followed by the pulsed helium plasma treatment with the specific energy of the incident flow Q = 40 J/cm² and pulse number N = 2, leads to the smoothing of the surface relief, compared to the initial state of the sample. There was observed the formation of the ordered submicrocrystalline cellular microstructure with the mean transverse size of the cell about 200 nm and significant surface hardening up to 7200 MPa.

This work was carried out within the center “Nuclear systems and materials” with the state support of the Program of increasing of competitiveness of National Research Nuclear University “MEPhI” (agreement with the Ministry of Education and Science of August 27, 2013; No. 02.а03.21.0005).

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