Rapid Consolidation of WC-ZrSiO4 Hard Materials by Spark Plasma Sintering: Microstructure, Densification, and Mechanical Properties

Jeong-Han Lee,Ik-Hyun Oh,Ju-Hun Kim,Sung-Kil Hong,Hyun-Kuk Park

doi:10.1007/s12540-021-00969-w

Abstract

Densely consolidated WC-based hard materials with 5–20 vol% ZrSiO4 was fabricated by spark plasma sintering at 1400 ℃ at a constant heating rate of 70 ℃/min−1. To achieve mechanical alloying of WC-ZrSiO4, planetary ball milling was carried out for 12 h, during which the brittle-brittle components (WC-ZrSiO4) became fragmented and their particles became refined. It was observed that certain, specific, non-isothermal sintering kinetics, such as apparent activation energy, sintering exponents, and densification strain, affected the densification behavior. The evolution of phase structure from powder to compact was found to be related the lattice distortion and micro-strain in the basal planes of WC. By examining the mechanical properties of the samples, it was that the added zircon content leads to enhanced fracture toughness (12.9 MPa m1/2) owing to the presence of WC-ZrSiO4 in the cemented carbide. In fact, the microcrack propagation of the fracture passed through zircon from a transgranular to a ductile component (fcc) where the crack tips could be absorbed.Graphic

Highlights

Hard materials, such as cemented carbide, cermets, and ceramic composites, have been widely used in cutting tools that are employed in machining various difficult-to-cut materials [1, 2]
The aim of this study was to obtain fully dense WC-ZrSiO4 hard materials from different powders varing in particle size and physical properties, and to observe how they prevent the dissociation of zircon due to the rapid consolidation of compacts in spark plasma sintering (SPS), which was preceded by the planetary ball milling process wherein the powders were mechanically alloyed
The derived crack bridging effect surrounded the precipitated zircon because of the crack deflection of tungsten carbide. This effect was Cemented carbide materials with zircon and improved toughness were produced in a fully densified state via SPS, which was preceded by the mechanical activation of the respective powders

Summary

Introduction

Hard materials, such as cemented carbide, cermets, and ceramic composites, have been widely used in cutting tools that are employed in machining various difficult-to-cut materials [1, 2]. WC-Co cemented carbides are the most popular because of their high stiffness, hardness, wear resistance, and temperature stability [3, 4]. Even when hard materials are used, the cutting tools are vulnerable to wear and tear, which softens the tools and reduces their lifespan, during the high speed and high temperature cutting process [5]. When maching conductive materials (workpiece) that heat up rapidly due to the discharge of electrictiy, the Co phase on the surface of the cemented carbide dissolves. This leads to the formation of a molten layer, which in turn causes the softening of the cutting tool [6, 7].

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Conclusion