Incorporation of tungsten carbide nanoparticles via colloidal processing in a mixture of powders for the formation of nickel aluminides formed in-situ by PTA

Abstract The intermetallic phases of the Ni-Al system are important due to their superior mechanical strength and outstanding magnetic and thermal properties, even under severe service conditions, such as high temperatures and oxidative atmospheres. The addition of nanoparticles to the matrix is an effective strategy to improve their properties even further. The aim of this study is to use the colloidal process to produce tungsten carbide (WC) nanoparticle carriers to be inserted into intermetallic Ni-Al phases formed in - situ. With this goal in mind, Ni carriers (2 μm to 3 μm) with 2.0 wt% of WC nanoparticles were produced by a colloidal process. Those carriers were subsequently homogenized with Ni and Al powders (75 μm to 150 μm), and then molten using plasma transferred arc. The samples were characterized by stereoscopy, high-resolution optical and scanning electron microscopy (FEG/EDS), X-ray diffraction (XRD) and Vickers microhardness. The results showed that the production of nickel with WC nanoparticles is achievable through colloidal processing. The amount of nickel in the carriers was considered enough to maintain the Ni/Al ratio in the in situ formation of the intermetallic compounds. The use of these carriers enables the addition of nanoparticles without their attaching to the surface of the metal powders, which suggests a reduction of diffusion barriers during the in-situ formation of intermetallic phases when compared to traditional impregnation methods.Furthermore, the inclusion of the WC nanoparticles increased the hardness of the deposited metal while preserving the ordered intermetallic phase, suggesting that the hardness gain can be primarily attributed to microstructural refinement, as indicated by the transition from dendritic to acicular structures.