Abstract
The reaction mechanism of ZrB2-ZrC formation in a 30% Ni-Zr-B4C system under argon was revealed by using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicated that the reaction mechanism in the Ni-Zr-B4C system was complex. Initially, NixZry and NixBy intermetallics were formed via solid-state diffusion reactions between Ni, B4C and Zr. Then, the eutectic reaction between Ni2B and Ni4B3 lead to the formation of Ni-B liquid. The free C atoms dissolved into the Ni-B liquid to form a Ni-B-C ternary liquid, and then part of the Zr powder dissolved into the surrounding Ni-B-C ternary liquid to form Ni-Zr-B-C quaternary liquid. Finally, ZrB2 and ZrC formed and precipitated out of the saturated liquid. The eutectic liquid plays an important role during the formation of ZrB2-ZrC.
Highlights
Formation in Ni-Zr-B4 C SystemBoride and carbide of zirconium (ZrB2 and ZrC) exhibit outstanding properties such as high hardness and melting points, low density as well as high resistance to corrosion and wear, which makes them attractive candidates for high-temperature ceramics, cutting tools, corrosion-resistant parts, reinforcing particles in the composites and wear resistant coatings [1,2,3,4,5,6]
Interrupted experiments were performed in order to elucidate the reaction mechanism during the heating process
The X-ray diffraction (XRD) result of differential scanning calorimetry (DSC) product heated to 1200 ◦ C shows that the product mainly consists of a large amount of ZrB2, ZrC and a small amount of Zr
Summary
Boride and carbide of zirconium (ZrB2 and ZrC) exhibit outstanding properties such as high hardness and melting points, low density as well as high resistance to corrosion and wear, which makes them attractive candidates for high-temperature ceramics, cutting tools, corrosion-resistant parts, reinforcing particles in the composites and wear resistant coatings [1,2,3,4,5,6]. In a previous paper [21], we successfully synthesized ZrC-ZrB2 /Ni cermet powders using a Ni-Zr-B4 C system by the SHS method. Scanning electron microscopy (SEM) were used to reveal the formation mechanism of ZrB2 -ZrC in the Ni-Zr-B4 C system during combustion synthesis. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. These preliminary results will be valuable for promoting the understanding of the reaction mechanism of ZrB2 -ZrC formation in the Ni-Zr-B4 C system
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