Enhanced densification and microstructural refinement in low-Ni WC composites: Conventional sintering optimisation

Resumen

Nickel is among the substitutes for Co as a binder in cemented carbides due to its higher corrosion resistance,
lower cost and critical availability. However, the low wettability of Ni in WC has limited the development of
cemented carbides with a low metal binder content, especially when sintered by conventional methods. In this
study, high-density WC-Ni cemented carbides, with 10 and 15 Ni vol% (5.9 and 9.1 wt%), were manufactured.
To ensure that metal particles were in contact with the WC and thus ensure homogeneous sintering, nanosized-Ni
(nNi, from now on) powders were dispersed in a matrix of micron-sized WC powders. Using colloidal processing
routes enables high and homogeneous dispersion of nNi throughout the entire volume of the part. Green samples
of the two compositions were pressureless sintered under high vacuum and flowing argon atmospheres, both at
1450 ºC and 1500 ºC. The best sintering condition resulted in being under high vacuum at 1450 ºC in terms of
microstructural parameters and hardness. Obtaining relative densities of 96.6 % and 97.2 %, WC grain sizes of
2.4 µm and 2.7 µm and Vickers hardness of 10.5 GPa and 9.3 GPa for WC/10Ni and WC/15Ni compositions,
respectively. Furthermore, plasticity mechanisms were evaluated by studying the microstructure of the hardness
indentation transverse plane.