A.G. Grigoryants

Laser surfacing of nickel-based composite war-resisting coatings reinforced with tungsten carbide

Abstract Investigations were carried out into the phase and structural state of the gradient coating produced by laser surfacing using tungsten carbide powders in a cobalt coating and a nickel alloy. The results show that the structure contains the WC carbide with the particles of the carbide forming spherical agglomerates, a nickel solid solution, alloyed with iron and cobalt, Me2W6 intermetallic phase, where Me = Fe, Cr and also CrO2 oxide. It is shown that the layers after reheating are characterized by the more extensive dissolution of the carbide and agglomerates and the formation of chromium-containing inclusions. The distribution of the elements and microhardness values in the cross section of the deposited coating was determined.

Optimization of the shape of nozzles for coaxial laser cladding

The results of mathematical modelling of the flows of powder in nozzles for coaxial laser cladding are presented. The modelling results are used to determine the optimum geometrical parameters of the nozzle used for the construction of appropriate technological equipment. Calculations are carried out to determine the optimum values of the flow rate of powder, the size of powder particles, the geometry of the powder flow and the distance from the outlet of the nozzle to the surface of the components. The resultant values were used in the development of technological processes of cladding with powders of different composition.

Technology of low-frequency vibrational treatment of welded structures in engineering

New equipment and technologies for low-frequency vibrational treatment of components in engineering are examined. The design of new equipment and its technological characteristics are described, the technology of stress relieving after welding, casting, machining, etc. is discussed, and equipment for inspecting the stresses prior to and after treatment is analysed.

Special features of laser welding using fibre and CO2 lasers

Investigations were carried out into the effect of different gas media on the process of welding in fibre lasers and comparison with CO2 lasers using the method of smooth variation of the position of the focal spot in relation to the surface of the welded specimens. The penetrating capacity of the metal was determined. Special attention is given to the effect of the density of the laser radiation power on the behaviour of plasma and the processes taking place in the weld pool in the welding in fibre lasers with a power of 2.5 and 5 kW. The effect of the intensity of laser radiation on the formation of the welded joint is described.

A device for removing metal from the weld pool when studying the shape of the weld pool

Abstract The dimensions and shape of a weld pool have a strong effect on both the technological and service parameters of welded joints. To investigate the shape and dimensions of a weld pool, a device for removing molten metal from the pool cavity for different materials and thickness of the welded specimens was designed and constructed. Investigation of the shape of the pool in laser welding showed special features of the pool in comparison with arc welding

Prospects for using laser radiation to improve cracking resistance in welding cryogenic steels

Abstract It is shown that in welding large structures with stable austenitic welding materials made of nitrogen-containing cryogenic chromium–nickel–manganese austenitic steels, cracks can form in the welded joint both during crystallization and in the solid-state at subsolidus temperatures. In laser welding, the structure of the cast weld metal can be greatly refined in comparison with arc welding and this should increase the solidification cracking resistance. In addition, laser welding can be used to produce the welded joint in a single pass thus preventing reheat cracking.

Development of technology and equipment for ultrasonic shock treatment of welded joints

Abstract New equipment and technology for ultrasonic shock treatment (UST) of components in engineering are described. The design of new equipment and its technical characteristics are outlined. Technology and the results of stress relief after welding, surfacing, pressure working and other operations are presented.

A system for automatic control of precision laser welding in engineering

A system for automatic control of the welding zone is described. The system can be used for positioning the focus of laser radiation in relation to the joint between the welded components without participation of the operator and also to control the temperature of the treatment zone.

Efficiency of the process of two-beam deep penetration laser welding

Numeral simulation of the interaction between laser radiation and surface plasma and welded component is conducted. Results of experimental investigations are given.

Investigation of thermal efficiency of treatment with the radiation of a high-power ytterbium-based fibre laser

Application effectiveness of a high-power fibre Yb-laser for the laser welding of metals is investigated. Expediency of the intensive laser welding conditions featuring maximal productivity and energy intensity is established.