Effects of nanocomposite grain growth inhibitors and multi-walled carbon nanotubes on the microstructure and mechanical properties of ultrafine cemented carbides

Obtaining cemented carbides with smaller WC grain size and better properties is key to their wider application. Ultrafine cemented carbides were prepared by using spark plasma sintering (SPS) with nano VC-Cr3C2 as nanocomposite grain growth inhibitors (NGGIs) and multi-walled carbon nanotubes (MWCNTs) as reinforcing materials. The effects of NGGIs and MWCNTs on the microstructure and mechanical properties of alloys were evaluated. The results indicated that the specimens (0.5 wt % NGGIs and 0.4 wt % MWCNTs) prepared at 1350 °C for 8 min under a pressure of 50 MPa have enhanced mechanical properties (HV 2520.85 kgf/mm2, KIC 13.26 MPa·m1/2) and a homogeneous microstructure. The grain size of WC is suppressed (the average grain size is 200-400 nm). NGGIs can prevent the dissolution of W and C in liquid Co, thereby inhibiting the growth of WC grains. The uniform dispersion of MWCNTs in WC matrix mobilizes their fiber-reinforcement effect. The combination of NGGIs, MWCNTs, and SPS can improve the mechanical properties and optimize the microstructure of the alloy.