Effects of carbon content on the microstructure and mechanical properties of MoCoB–Co cermets.

MoCoB–Co cermets with varying carbon contents were synthesised using reactive boronizing sintering, followed by an investigation into their microstructure and mechanical properties. Adding an appropriate amount of carbon facilitates the wetting of liquid on ceramic particles and improves the density of the cermets. However, excessive carbon addition can render some carbon insoluble, leading to a reduction in density. With the increase in carbon content, the pores transition from spherical to irregular shapes, and the MoCoB particles shift from equiaxed to long rod-like structures. The presence of long rod-like MoCoB particles promotes crack deflection and transgranular fracture, thereby improving the toughness of the material. The bonding strength of the MoCoB/hcp-Co interface is higher than that of the MoCoB/fcc-Co interface. Carbon addition increases the hcp-Co content in the binder phase, further improving the toughness of the material. Cermets with a 0.5 wt% carbon additive exhibit outstanding mechanical properties, including a hardness, transverse rupture strength and fracture toughness of HRA 91.5, 1967 MPa and 15.3 MPa m1/2, respectively. [ABSTRACT FROM AUTHOR]