Structural Features of a Heat Affected Zone with Pulsed Arc Surfacing of Railway Crossovers

Results are provided for structural studies and mechanical property evaluation of surfacing layers prepared by pulsed arc surfacing with austenitic wire A7-1G on high-carbon steel É76 during production of railway crossovers. Welding and surfacing of various materials, especially if one of them has a high carbon content, is an important practical task connected with obtaining an effective surfacing layer structure and heat-affected zone. Use of light and scanning electron microscopy methods shows that pulsed arc melting makes it possible to form various austenitic and pearlitic steel compounds, and within the heat-affected zone in carbon steel a fine ferrite-pearlite mixture with a minimum ferrite grain size of 1 μm is present. Features of the ferrite formed in this case are its irregular shape, curvature, interrupted nature, and defects in the form of discontinuities. Part of the cementite undergoes transformation into granular form. These features of the heat affected zone structure are favorable from the point of view of providing the crack resistance indices required for the joints obtained. It is demonstrated that with tests by a three-point bending scheme for crossover elements the failure load increases by 15% compared with welded joints of the same steels.