Structural-phase composition and mechanical properties of stainless steel – low carbon steel metal composite

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The subject of the study is a metal composite obtained by electric arc surfacing in argon of corrosion–resistant steel on low-carbon steel. Powdered chromium-nickel steel was deposited with an increased content of silicon and molybdenum relative to the traditional composition. In this work, we studied the elemental and structural-phase compositions, as well as the mechanical properties of both components of the material and the composite as a whole in the initial state and after annealing at 680 °C for 3 h. The main part of the corrosion-resistant component is a two-phase auste­nitic-ferritic mixture with a ratio of 65 % HCC phase and 30 % BCC phase. The material has high microhardness (more than 4000 MPa). The highest microhardness (4550 MPa) is observed in a narrow strip of deposited metal with a width of 25 μm, where the phase composition is represented by martensite (BCC), and austenite is absent. The transition across the boundary into carbon steel is accompanied by a decrease in microhardness to 1225 MPa. Here, a decarbonized zone with a width of 180 μm was formed near the fusion line. The resulting non-equilibrium stress-strain state of the composite led to low strength, low plasticity and brittle fracture of the deposited layer during tensile testing. After annealing, microstructure of the corrosion-resistant component became more uniform in size of both austenitic and ferritic structural elements. As a result of these transformations, internal stresses decreased and microhardness decreased to 3100 MPa. At the same time, the width of the decarbonized zone in the base metal increased. All these changes led to the fact that, although the tensile stress of the annealed material increased by 8 %, and the deformation to rupture – by 27 %, however, nature of the fracture remained brittle and rupture still occurs along the deposited layer. This is determined by the austenitic-ferritic phase composition of the stainless component, which, in turn, is determined by chemical composition of the deposited material.