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artin Hörner and Bernhard Blug Fraunhofer IWM, Fraunhofer Institute for Mechanics of Materials, Freiburg im Breisgau 79108, Germany

Maike van Geldern KSB Aktiengesellschaft, Pegnitz 91257, Germany

Alexander Michaelis and Mathias Herrmann Fraunhofer IKTS, Fraunhofer Institute for Ceramic Technologies and Systems, Dresden 01277, Germany (Received 27 January 2017; accepted 16 May 2017)

Extremely hard, wear-resistant SiC-bonded diamond materials with diamond contents of approximately 45–60% by volume can be prepared by pressureless infiltration of shaped diamond compacts with silicon. Materials with diamond grain sizes in the range of 10–100 lm can be produced having a free silicon content of less than 5 vol%. Components with large dimensions can be prepared as graded or ungraded materials. Graded components are composed of silicon infiltrated SiC base material with diamond–SiC composite layers of 0.1 mm by dip coating technology to several mm in thickness by doubled die pressing in regions with high loading. This creates the possibility of producing low-cost, wear-resistant components of various geometries and dimensions with bending strengths of 400–500 MPa, hardness values of 48 GPa, and fracture toughness levels of 4.5–5 MPa m1/2 for use in extreme wear conditions. Thermal conductivities of up to 500 W/(m K) were obtained, render these materials interesting for heat sinks.

I. INTRODUCTION

Wear-resistant ceramic components are essential to modern industry. Ever-higher demands on these components and new technological possibilities are driving the development of new wear-resistant materials. It is not surprising that extremely wear-resistant materials are typically based on materials containing diamond or cubic boron nitride (cBN). Over the last few years the costs of diamond grit has dropped strongly, making new applications possible. The main disadvantage of these materials is the need to manufacture them using high-pressure synthesis, which limits their use due to high costs and geometrical restrictions.1–3 Hence, lower-cost superhard materials and technologies for manufacturing them are highly sought after. Manufacturing of SiC-bonded diamond materials represents a promising way to obtain low-cost, superhard, wear-resistant materials.4–18 SiC–diamond composites can be produced through reactive sintering of powders or infiltration of diamond preforms with silicon. Requirements for preparing dense, fine-grained materials by reaction sintering of diamond

Contributing Editor: Nahum Travitzky a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.218

and silicon powder can be quite elaborate. Ko et al.6 prepared dense polycrystalline samples with diamond grain sizes of less than 1 lm and SiC bonding by highpressure sintering at 6 GPa. Reaction sintering of finegrained diamond materials has been performed using the capsule HIP method. However, it does result in a certain amount of residual porosity.7 This is caused by the large volume change accompanying the reacti