Analysis of the current state of additive welding technologies for manufacturing volume metallic products (review)

Using of welding technologies to produce metal volume objects allows considerable lowering of their manufacturing cost at simultaneous increase in productivity, compared to SLS-and SLM-processes. The most perspective welding technology of additive manufacturing of three-dimensional objects is plasma-arc technology with application of wires or powders. It allows creating at comparatively low heat input quality volumetric products with wall thickness from 3 to 50 mm from alloys based on Fe, Ni, Co, Cu, Ti, Al, as well as composite materials, containing refractory components.

The theoretical analysis of the influence of the plasma discharge temperature with non-consumable electrode on the melting of the electrode wire was carried out. The dynamics of the melting of the electrode wire and dynamics of circuit with consumable electrode arc were been investigation. The estimation of maximum values of the temperature of plasma have been made. Influence of the MIG process on the volt-ampere characteristics of the plasma discharge have been studied. These results were used for carrying out the technological experiments.

The paper is devoted to the analysis of the history of the creation of the laser as one of the greatest technical inventions of the 20th century. This paper focuses on establishing a relation between the periodization of the stages of creation and implementation of certain types of lasers, with their influence on the invention of certain types of equipment and industrial technologies for processing the materials, the development of certain branches of the economy, and scientific-technological progress as a whole. In preparing the paper, the generally accepted methods, which are widely used in the preparation of historical research works, have been applied: the historical method – for the study and interpretation of the texts of primary sources and the search for other evidence used for research, as well as for the presentation of historical events associated with the development of laser technology; the historical-genetic method – for studying the genesis of specific historical phenomena and analyzing the causality of changes in the development of laser technology; the historical-critical method – for displaying cause-and-effect relationships, reconstructing events that influenced the development of laser technology; the method of historical periodization. The variety of different possible options for the use of lasers did not allow placing all the collected materials within the framework of one paper, and therefore, the authors have decided to dwell on the facts, which, in the opinion of the paper’s authors, are the most interesting, significant, poorly studied, and little known. The paper discusses the stages of: invention of the first laser; creation of the first commercial lasers; development of the first applications of lasers in industrial technologies for processing the materials. Special attention is paid to the “patent wars” that accompanied different stages of the creation of lasers. A comparative analysis of the market development for laser technology from the stage of creation to the present has been carried out. It has been shown that the modern market for laser technology continues to develop actively, as evidenced by the continued stable growth of laser sales over the past 10 years. This indicates that the demand for laser technology is inextricably linked with the development of high technology production and scientific-technological progress. The analysis has shown that recently, the trends in the use of laser technology have changed; in particular, their industrial and medical applications are decreasing, while there is an increase in their use in the fields of sensor production and communication.

Multi-pass laser and laser-arc narrow-gap welding make it possible to obtain high-quality butt joints of large-thickness pipe steels with hardness up to 2600...2800 MPa and toughness close to the base metal toughness at a temperature of 20°C. When multi-pass welding methods are used, the subsequent pass makes heat treatment of the previous ones, and reduces the rate of their cooling yet. This allows excluding heat treatment of the joint after welding, which significantly reduces the time and costs for manufacturing large-sized structures.

This paper reports a study into the regularities of interphase interaction, features in the formation of intermetallic phases (IMPs), and defects when surfacing steel on titanium in four ways: P-MAG, CMT, plasma surfacing by an indirect arc with conductive wire, and PAW. A general tendency has been established in the IMP occurrence when surfacing steel on titanium by all the considered methods. It was determined that the plasma surfacing technique involving an indirect arc with conductive wire is less critical as regards the IMP formation. That makes it possible to obtain an intermetallic layer of the minimum thickness (25...54 μm) in combination with the best quality in the formation of surfaced metal beads. Further minimization of the size of this layer is complicated by a critical decrease in the heat input into the metal, which gives rise to the capability of the surfaced metal to be collected in separate droplets. The formation of TiFe2, TiFe, and the α-Fe phase enriched with titanium in different percentage compositions has been observed in the transition zone of steel surfacing on titanium under different techniques and modes of surfacing. The study has shown the possibility of formation, in addition to the phases of TiFe2 and TiFe, the Ti2Fe phase at low heat input. The technique of plasma surfacing by an indirect arc with conductive wire minimizes the thermal effect on the base metal. When it is used at the border of the transition of the layer of steel surfaced on titanium, the phase composition and structure of the layers in some cases approach the composition and structure of the transition zone of the original bimetallic sheet "titanium-steel" manufactured by rolling. A layer up to 5 μm thick is formed from the β phase with an iron concentration of 44.65 % by weight and an intermetallic layer up to 0.2...0.4 μm thick, close in composition to the TiFe phase. The next step in minimizing the IMP formation might involve the introduction of a barrier layer between titanium and steel.