Pressureless Sintering of Titanium Diboride with Nickel, Nickel Boride, and Iron Additives

Abstract

The effect of relatively small additions (1-5 wt%) of nickel, nickel boride (NiB), and iron to promote the liquid-phase sintering of titanium diboride (TiB 2 ) has been studied. Carbon also was added to some samples, to reduce the amount of oxygen impurities in the TiB 2 ceramics. Green bodies that were formed by uniaxial pressing were sintered in a graphite furnace at 1300°-1700°C, both under vacuum and in a 500 mbar argon atmosphere, and high densities (>94% of theoretical density) were obtained at temperatures ≥1500°C. The weight loss of the samples during sintering was shown to be dependent on the densification rate and the final density and was not governed only by the thermodynamics of the system. Significant exaggerated grain growth was observed in samples with nickel, NiB, and iron during sintering at 1700°C. The exaggerated grain growth was observed to be closely related to the oxygen content of the samples and to temperature. The addition of carbon strongly reduced the density and the oxygen content and, thereby, inhibited grain growth. We have proposed that the exaggerated grain growth is enhanced by surface diffusion in a titanium-oxide-rich layer on the TiB 2 grains.

Microstructural development and hardness of TiB2–B4C composite samples: Influence of consolidation temperature

“…A titanium-based ceramic material of interest in the industrial sector is titanium diboride (TiB 2 ). It offers the potential for use in areas of cutting tools, wear resistant the end product does not exceed 95% of the theoretical value [8]. TiB 2 has relatively low crystalline boundary diffusion coefficient, which promotes slow densification and thus requiring prolonged sintering times.…”

Effect of Hot‐Pressing Temperature on Densification and Mechanical Properties of Titanium Diboride with Silicon Nitride as a Sintering Aid

“…This result is in contrast to the case of transition-metal additions, where extensive grain growth occurs with densification. 4,5 This microstructural evolution suggests that, to densify TiB 2 at low temperatures, the elimination of the oxide layer is necessary and the formation of a liquid phase during sintering is crucial.…”

Preparation and Characterization of TiB2-(Supra-Nano-Dual-Phase) High-Entropy Alloy Cermet by Spark Plasma Sintering

“…Nanoparticles are conspicuous in the liquid phase of HEA, with a size of 5-10 nm embedded in the amorphous phase. Fast Fourier Transform (FFT) image indicates that these nano-precipitates are simple face-centered cubic (FCC) structures [12]. It is known that the structure of CoCrFeNiAl HEA is body-centered cubic (BCC) following synthesis with the MA process, but the BCC phase prepared in the non-equilibrium process is metastable, and the CoCrFeNiAl HEA will be converted into an FCC structure beyond 1000 • C, according to our previous research [20,25].…”

“…However, their effect on lowering the sintering temperature is not obvious. Some transition metallic elements, such as nickel, iron, and titanium have been tested as binders [11][12][13][14]. Compared with AlN et al, metals have better wettability with TiB 2 .…”