Abstract
Owing to their extreme hardness, cubic boron nitride (cBN) composites are widely used in cutting applications. The performance of cBN composites is closely related to the characteristics of the binder. Therefore, novel binders must be developed to improve the performance of cBN composites. In the present work, TiAl intermetallics were used as binders to fabricate cBN composites by employing a high-temperature and high-pressure sintering method. The phase transformation, sintering reaction mechanism, thermal stability, and mechanical properties of the resultant cBN composites were investigated. It was found that during the sintering process, Ti atoms preferentially reacted with boron nitride particles, whereas Al atoms enriched and transformed into TiAl3 phases and formed cBN/AlN, AlB2/TiN, and TiB2/TiAl3-layered structures eventually. The composites maintained good oxidation resistance at 1200 °C. A decrease in the particle size of the TiAl binder improved the uniformity of particle size distribution and increased the flexural strength of the composites.
Highlights
Introduction as a Binder on CubicBoron NitrideCubic boron nitride has excellent hardness, wear resistance, thermal stability, and chemical inertness
When MAX phases, such as Ti3 AlC2 and Ti3 SiC2, are used to sinter polycrystalline cubic boron nitride (PcBN), they decompose under high temperatures and high pressure
The current study presents the results of using high-temperature and high-pressure sintering to prepare PcBN composites by using TiAl as a binder
Summary
Cubic boron nitride (cBN) has excellent hardness, wear resistance, thermal stability, and chemical inertness. In comparison to other intermetallic compounds, γ-TiAl has a higher oxidation resistance, a higher specific melting point, and superior high-temperature stability. It is considered as a potential PcBN binder. (5) TiAl can maintain the intermetallic structure during the sintering process and form a matrix-reaction product-intermetallic compound, which help to retain the advantages of using a metallic binder for a complete bonding. This process can avoid the presence of metal residues and maintain good mechanical properties at high temperatures. The sintering mechanism and the effects of the grain sizes of binder particles on the uniformity and controllability of PcBN structures were systematically investigated
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