Effect of the hot-wire laser irradiation method and a Ni-based alloy middle layer on mechanical properties and microstructure in additive manufacturing of WC–Co cemented carbide

In fabrication of WC–Co cemented carbide, the mechanical properties of the fabricated object deteriorate in the presence of porosity defects and W 2 C, which is generated by WC decomposition. To fabricate cemented carbide objects without such defects, this study investigated additive manufacturing using the hot-wire laser method with sintered rod-shaped cemented carbide (WC–16 %Co). To evaluate the effect of the laser beam irradiation method on the fabricated cemented carbide, two fabrication methods were carried out: one in which the rod leads the direction of fabrication (the laser directly irradiates the top of the cemented carbide rod), and one in which the laser leads the direction of fabrication (the laser irradiates between the bottom of the cemented carbide rod and the base material). With the rod leading, WC decomposition was observed in the upper part of the object, where the laser directly irradiated, and many defects were observed. However, with the laser leading, the WC decomposition was suppressed, but the base material element Fe invaded the fabricated structure, causing a decrease in hardness. Fabricating a middle layer consisting of a Ni-based alloy to suppress the influence of the base material achieved a WC–Co cemented carbide object with a sufficient hardness of over 1400 HV without WC decomposition or any defects. • A new additive manufacturing method using hot-wire laser method with sintered cemented carbide rods was developed. • Direct laser irradiation of the cemented carbide causes decomposition of the WC. • A Ni-based alloy intermediate layer prevents degradation of the cemented carbide structure's properties. • Successfully fabricated a cemented carbide body with no change in hardness and grain size.