Effects of Cr3C2, VC, and TaC on Microstructure, WC Morphology and Mechanical Properties of Ultrafine WC–10 wt. % Co Cemented Carbides

Chao Yin,Jianming Ruan,Yong Du,Yingbiao Peng,Jianzhan Long,Kai Li

doi:10.3390/met10091211

Abstract

In this study, the effects of Cr3C2, VC, and TaC on microstructure, WC grain morphology and mechanical properties of WC–10 wt. % Co ultrafine cemented carbides were investigated. The experimental results showed that WC grains size decreased and size distribution became narrow by adding Cr3C2, VC, and TaC. The inhibition efficiency was in the order of VC > Cr3C2 > TaC. Cr3C2 addition would induce triangular prism grains and Co phase was strengthened by Cr3C2, resulting in the enhancement of transverse rupture strength (TRS) and impact toughness. WC morphologies in cemented carbides with VC addition were triangular prisms with multi-steps in basal and prismatic planes due to anisotropic growth. The multi-steps in basal and prismatic planes led to low TRS and fracture toughness. The inhibition mechanism of TaC is to reduce the surface energy of WC and slow down the solution/re-precipitation rate at the WC/Co interfaces by adsorbing on the surface of WC grains. The sample with 0.8 wt. % Cr3C2 had excellent comprehensive mechanical properties. Its Vickers hardness, fracture toughness, TRS and impact toughness were 1620 kg/mm2, 9.94 MPa·m1/2, 3960 MPa and 50.4 J/m2, respectively. In summary, Cr3C2 is the first choice as the grain growth inhibitors (GGI) for the preparation of ultrafine cemented carbides.

Highlights

Due to their high hardness, wear resistance and fracture strength, the WC–Co cemented carbides have been extensively used in industries, such as cutting, machining, mining, and drilling tools [1].As the increasing cutting speed and efficiency is in great demand for cutting high performance materials, further improvement of their mechanical properties are urgently needed
Previous studies have shown that the mechanical properties of WC–Co cemented carbides can be substantially increased when WC grain size decreases to submicron and nanometer scale [2,3,4,5]
The local composition was measured by the energy dispersive X-ray (EDX) spectroscopy performed on the microstructures

Summary

Introduction

Due to their high hardness, wear resistance and fracture strength, the WC–Co cemented carbides have been extensively used in industries, such as cutting, machining, mining, and drilling tools [1]. Previous studies have shown that the mechanical properties of WC–Co cemented carbides can be substantially increased when WC grain size decreases to submicron and nanometer scale [2,3,4,5]. With the addition of VC, multi-steps in WC grains were deemed to cause stress concentrations on loading and increase the sensitivity to cracking, resulting in low TRS and fracture toughness [20]. No systematic comparison of the effects of Cr3 C2 , VC, or TaC on the microstructure, WC morphology, and mechanical properties of ultrafine cemented carbides has been performed. The effects of Cr3 C2 , VC, and TaC on microstructure, WC morphology, and mechanical properties were investigated and compared to the samples without any GGI. The results may provide a scientific basis for selecting GGIs during ultrafine cemented carbide production

Materials Preparation

Characterization

Microstructure and Phase Constitution Analysis

Mechanical Properties and Fracture Morphology

Conclusions