Anatoliy M. Orishich

Results of a series of experiments aimed at studying laser cladding of individual tracks with the use of the B₄C–Ti–6Al–4V cermet powder mixture are reported. The influence of laser cladding parameters (radiation power, beam motion velocity, and focus position) on the characteristics of tracks being formed (geometric sizes, microhardness, and elemental composition) is studied. It is shown that an increase in the concentration of reinforcing particles in the initial powder mixture alters the character of mass transfer inside the melt pool, leading to changes in the shape of the single track. It is found that a complex heterogeneous structure is formed in the melt pool, including secondary phase compounds formed in chemical reactions due to in-situ synthesis. The microhardness values at various points of the single track are observed to differ by more than a factor of 2 (in the interval HV_0.3 = 548–1415).

The experimentally observed evolution of unstable plastic flow of laser-welded specimens of Al–6Mg–2Li, Al–1.6Cu–1.1Mg–1.8Li, and Al–3.4Cu–0.66Mg–1.5Li aluminum–lithium alloys under different heat treatment conditions after welding was analyzed. A comparison of the jerky flow of alloys with different concentrations of magnesium, copper, and lithium was performed. The effect of copper on the spatial consistency of the localized shear bands formed in aluminum–lithium alloys under unstable plastic flow was studied.

Results of an experimental study of the strength characteristics and structural-phase composition of a nondetachable connection of dissimilar materials based on thermally hardened aluminum alloys D16T of the Al-4.4Cu-1.5Mg system and 1420 of the Al-5.2Mg-2.1Li system obtained by butt-end laser welding are reported. The phase composition of the welded joint is studied with the use of synchrotron radiation by the method of transmission diffraction. The welded joint microstructure is considered by optical microscopy. It is demonstrated that heat treatment (quenching and artificial aging) allows one to improve the chemical properties of the welded joint.

Results of theoretical and experimental investigations of physical and mechanical properties of a heterogeneous material based on the TiB ceramics and Ti–6Al–4V metallic alloy obtained by means of selective laser melting are reported. Elastic properties of the heterogeneous structure under analysis are described by the method of conditional moments. Young’s modulus of the created heterogeneous material based on the titanium alloy and titanium boride is measured. The experimental data are found to be in good agreement with the numerical predictions.

The paper presents the results of an experimental study of the microstructure and microhardness of a functionally gradient material fabricated from 316L stainless steel and tungsten carbide (WC) ceramic particles by the selective laser melting method. High-quality defect-free cermet coatings with different ceramic contents were obtained. Optical and scanning electron microscopy and energy dispersive analysis show that laser processing leads to dissolution of WC ceramic particles. The produced coating has a dendritic structure and contains iron- and chromium-based carbides. The coating microhardness is in the range HV_0.3 = 280 – 430.

One of the most promising methods of spraying protecting coating is the laser coating with strengthening phases, alloying or modifying elements. The purpose of this study is the creation of composite wear and corrosion resistant coatings by additive technology of laser coating for oil and mining industries. The possibility of obtaining complex coating with a strengthening phase is shown. Two variants of coating were considered. Variant 1: support plate made of 12Х18Н10Т stainless steel was cladded with sublayer made of Ni + Cr powder, afterwards the upper cladding layer made of Х23Н5М3ГС steel of Cr-Ni-Мn system was formed with various content of strengthening WC phase in the form of VK-12 powder. Variant 2: support plate made of carbon steel was cladded with four layers of self-fluxing cladding powder PS-12NVK-01 of Ni-Cr-Fe / WC system with addition of nanomodification of powder TiN + Y2O3 + Cr + Fe. The specialists established the dependence of microstructure, structural-phase components and micro hardness of cladded layer from the quantity of WC strengthening phase. The various content of WC strengthening phase (from 10 to 30 %) does not influence the micro hardness of the upper layer significantly – it’s average value is ≈ 700 HV The laser influence on powder mixture leads to partial deterioration of WC strengthening phase, which leads to chemical reaction of tungsten cobalt powder and stainless steеl with formation of complex intermetallic compounds and carbides. Small addition of nanosized modifier TiN + Y2O3 (0,1 % of weight) in a composite mixture with coating power PS-12NVK-01 allows increasing the hardness of protective coating by 1.4, and wear-resistance – by 2 times in comparison to the coatings with similar characteristics, obtained without nanomodifying additions.

This paper describes the experimental study of strength characteristics and the microstructure of a permanent joint of dissimilar materials (VT20 titanium alloy and V-1461 aluminum alloy), obtained by laser butt welding. Optical and electron microscopy, X-ray spectral and phase analysis, and the transmission diffraction method with the help of synchrotron radiation are all used to investigate the properties of a weld. It is shown that the laser radiation offset relative to the contact surface of dissimilar materials significantly changes the microstructure and phase composition of the intermetallic interlayer formed between the materials welded, thereby affecting the strength of dissimilar welded joints.

Results of an experimental study of how temperature affects the fracture of laser welded joints of an Al-Cu-Li aircraft aluminum alloy are presented. A comparison is made of the deformation and fracture of welded joints in the initial state and after two-step heat treatment. It is shown that the mechanical characteristics of welded samples have values close to those of the initial alloy.

The paper presents the investigation of the laser welding of the alloy Al-Cu-Li and titanium alloy Ti-Al-V, as well as the analysis of the post=processing on the strength properties of welded joints. Macro- and micro-structure of the joints have been studied. The resulting heterogeneous welded materials have been post-processed. The mechanical characteristics of the welded joints have been determined before and after the thermal processing.