Wire-arc additive manufacturing (WAAM) is considered as a rather promising alternative to conventional subtracting production process for manufacture of large expensive metal components with complicated geometrical shape. Up-todate direction of WAAM investigations is aimed on production of functional metallic components with complicated geometrical shape and high accuracy, surface processing and mechanical properties meeting the strict requirements of aerospace, automotive and instrumental industries. At the same time, structural application of metal components based on their mechanical properties is studied insufficiently. It is necessary to understand additionally influence of technological conditions (such as energy input, protective gas role, speed of wire feed, welding speed, facing features and its sequence etc.) on the thermal initial parameters and finishing mechanical properties. The paper displays that mechanical properties of low-alloyed silicon-manganese composition of C-Mn-Si type with ferrite-pearlite structure is higher comparing with conventional steel 09G2S. It is shown that impact strength values for C-Mn-Si-type composition, which id formed via WAAM method, is higher by 2 times in comparison with welded joints which are faced by Sv-08G2S wire.

The results of study of impact strength of C-Mn-Si composition metal after wire-arc additive manufacturing (WAAM) are presented. It was established that destruction of the samples of such composition at the temperatures below tough-brittle transition occurs both via tough and brittle mechanisms. The samples manufactured in the direction along built-up welding are characterized by essentially lower impact strength comparing with those manufactured in vertical direction of samples cutting. Impact strength of the samples made of 09G2SA standard steel is substantially lower than for C-Mn-Si composition metal which was obtained via additive technology. Fractographic analysis of fractures for C-Mn-Si compositions manufactured via additive technology using carbon dioxide and gas mixture displays tough pit destruction type. The samples with high impact strength are characterized by forming of cleavage facets after tough crack propagation to the sample middle, what is accompanied by significant widening opposite to a notch and narrowing under a notch. The samples with low impact strength are characterized by forming of brittle fracture directly under a notch without essential sample plastic deformation. It is shown that built-up welding with partial or complete recrystallization of rolls is required for forming of cold-resistant metal structure. In this case, order of rolls location, heat input and parameters of welding conditions make the direct effect on shape, geometrical dimensions, fusion penetration and number of rolls, as well as on size and morphology of the structural components, percent relation between cast and recrystallized microstructure of seam metal. The complex of these factors finally determines structural state and cold resistance of seam metal.

The article presents the results of the study of the effect of laser treatment on the structure and microhardness of the surface of high-carbon steel samples. The treatment is carried out in order to obtain surface layers, parts with high properties for industries of various purposes. The samples from high-carbon steel U10 A after preliminary thermal treatment by modes of 780–800 °C heating for 2 minutes with cooling in 10 percent water solution of sodium chloride with tempering at 270–320 °C and cooled in the air and without the thermal treatment are treated with the Nd:YAG laser with the capacity up to 1 kW. Metallographic studies and microhardness properties illustrate the influence of laser surface processing on the increase in mechanical properties. It is shown that the laser thermal treatment of steel allows obtaining a surface microhardness of about HV 800-1000 MPa and depends on the original state of the metal and the previous thermal treatment.