Structural-phase state and properties of 56GM/(W + WC(Ni)) composite alloy obtained by wire electron beam additive manufacturing

The authors investigated the microstructure and mechanical characteristics of 56GM steel-based composite produced by wire electron-beam additive manufacturing with the addition of W + WC(Ni) powders during printing. The analysis demonstrates that 56GM/(W + WC(Ni)) composite alloy is characterised by a gradient structure consisting of 56GM base layer, 56GM – 56GM/(W + WC(Ni)) intermediate layer and 56GM/(W + WC(Ni)) composite layer. The base layer of 56GM steel is characterized by a multidirectional acicular structure, which corresponds to the ferrite-martensite state. In 56GM – 56GM/(W + WC(Ni)) intermediate layer the acicular structure becomes less pronounced. In 56GM/(W + WC(Ni)) composite layer an equiaxed grain structure is formed, with an average grain size of 8.59 μm, along the boundaries of which cracks are observed. WC particles are located mainly along the boundaries of small grains and in small quantities inside the grains themselves. It was found that 56GM/(W + WC(Ni)) composite is mainly composed of α-Fe (~80.6 vol. %), Ni (~6 vol. %), WC carbide phase (~10.3 vol. %) and γ-Fe (3 vol. %). The structure and properties of initial 56GM steel change both in the area of direct addition of alloying powder and in the underlying layers due to diffusion processes and infiltration of W + WC(Ni). Microhardness values increase from ~3.5 GPa to ~6.5 GPa with distance from the substrate to the composite layer. In uniaxial tensile tests, the ultimate tensile strength and yield strength values reached 1100 – 1200 MPa and 835 MPa in the intermediate layer, respectively.