WC-Co additive manufactured depositions on a HSS 390 steel substrate: a microstructural investigation

The Direct Energy Deposition (DED-AM) is a novel 3D printing process widely employed for building layer by layer components for several industrial fields, such as biomedical, aerospace and automotive. WC-Co is a well-known cermet coating for tribological applications, mainly characterized by the dispersion of WC particles into a Co matrix acting as a binder. Considering its high wear resistance as well as its high hardness and strength, the thermal spraying technique is commonly used to perform WC-Co coatings on several substrates, but currently DED may be successfully employed as an alternative manufacturing process. In the present study, WC-12%Co powders were deposited on the HSS 390 tool steel using two DED- laser deposition methods and different process parameters; power, scanning speed and feed rate were appropriately changed in order to consider their effect on the microstructural properties of the hardfacing material. Microstructural analyses were carried out by means of optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Preliminary results demonstrated that the use of different deposition methods as well as the number of layers could significantly affect the distribution of phases across the additive manufactured coating. Moreover, the results obtained by this experimental investigation enabled to suggest possible optimization of the process parameters to prevent the presence of different defects such as cracks and porosity.